WDIFF

draft-ietf-rsvp-spec-09.txt --> draft-ietf-rsvp-spec-10.txt

Internet Draft R. Braden, Ed.
Expiration: August 1996 ISI
File: draft-ietf-rsvp-spec-09.txt draft-ietf-rsvp-spec-10.txt L. Zhang
PARC
S. Berson
ISI
S. Herzog
ISI
S. Jamin
USC

Resource ReSerVation Protocol (RSVP) --

Version 1 Functional Specification

February 12, 21, 1996

Status of Memo

This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

To learn the current status of any Internet-Draft, please check the
linebreak
"1id-abstracts.txt" listing contained in the Internet- Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim).

Abstract

This memo describes version 1 of RSVP, a resource reservation setup
protocol designed for an integrated services Internet. RSVP provides
receiver-initiated setup of resource reservations for multicast or
unicast data flows, with good scaling and robustness properties.

Braden, Zhang, et al. Expiration: August 1996 [Page 1]

Internet Draft RSVP Specification February 1996

Table of Contents

1. Introduction ........................................................4 ........................................................5
1.1 Data Flows ......................................................7 ......................................................8
1.2 Reservation Model ...............................................8 ...............................................9
1.3 Reservation Styles ..............................................10 ..............................................11
1.4 Examples of Styles ..............................................13 ..............................................14
2. RSVP Protocol Mechanisms ............................................18 ............................................19
2.1 RSVP Messages ...................................................18 ...................................................19
2.2 Port Usage ......................................................20 ......................................................21
2.3 Merging Flowspecs ...............................................21 ...............................................22
2.4 Soft State ......................................................22 ......................................................23
2.5 Teardown ........................................................24 ........................................................25
2.6 Errors ..........................................................25 ..........................................................26
2.7 Confirmation ....................................................27 ....................................................28
2.8 Policy and Security .............................................27 .............................................28
2.9 Automatic RSVP Tunneling ........................................28 ........................................29
2.10 Host Model .....................................................29 .....................................................30
3. RSVP Functional Specification .......................................31 .......................................32
3.1 RSVP Message Formats ............................................31 ............................................32
3.2 Sending RSVP Messages ...........................................44 ...........................................45
3.3 Avoiding RSVP Message Loops .....................................45 .....................................47
3.4 Blockade State ..................................................49 ..................................................50
3.5 Local Repair ....................................................51 ....................................................52
3.6 Time Parameters .................................................52 .................................................53
3.7 Traffic Policing and Non-Integrated Service Hops ................53 ................54
3.8 Multihomed Hosts ................................................54 ................................................56
3.9 Future Compatibility ............................................56 ............................................57
3.10 RSVP Interfaces ................................................58 ................................................59
4. Message Processing Rules ............................................70 ............................................71
5. Acknowledgments .....................................................89 .....................................................90
APPENDIX A. Object Definitions .........................................90 .........................................91
APPENDIX B. Error Codes and Values .....................................106 .....................................107
APPENDIX C. UDP Encapsulation ..........................................111 ..........................................112

Braden, Zhang, et al. Expiration: August 1996 [Page 2]

Internet Draft RSVP Specification February 1996

What's Changed

The most important changes in this document from the rsvp-spec-09
draft are:

o Multiple POLICY_DATA objects in any order are now allowed.

o The length field in the common header is now the total
message length [Section 3.1.1].

o The meaning of Message Id is refined and more completely
specified [Section 3.1.1].

o RSVP fragmentation is specifically called for, and IP
fragmentation disallowed [Section 3.1.1].

o The granularity of state timeouts is now specified [Section
3.6].

The most important changes in this document from the rsvp-spec-08
draft are:

o The handling of reservation errors has been fundamentally
changed, to prevent the "second killer reservation problem".
A new kind of state has been introduced into a node,
"blockade state", which is created by a RERR ResvErr message with
Error Code = 01, and which controls the merging process for
generating reservation refresh messages [Sections 2.6 and
3.4].

o RSVP now carries two flag bits in the SESSION object to
indicate to a receiver whether there are non-RSVP-capable
nodes along the path to a given sender [Sections 2.9 and
3.7].

o The optional INTEGRITY object is now specified to immediately
follow the common header and to appear in every fragment
[Section 3.1].

o There are now two flag bits in an ERROR_SPEC object: InPlace
and NotGuilty [Section 3.10].

o The text now states that implementations should be as
permissive as possible in accepting objects in any order
within a message (and required ordering is specified), but

Braden, Zhang, et al. Expiration: August 1996 [Page 3]

Internet Draft RSVP Specification February 1996

they should follow the BNF-implied order in creating a
message.

o The text now states that IP fragmentation of data packets is
generally not possible when RSVP is in use, since the TCP/UDP
port fields may be required for classification [Section 1.2].

o The rules for handling an unrecognized object class are
changed to include a third possibility: ignore and do not
forward the object [Section 3.9].

o All generic Traffic Control calls are modified to include an
interface specification, allowing the Thandle to be
interface-specific [Section 3.10.2].

o Disabling an interface for RSVP is allowed [Section 3.10.3].

Braden, Zhang, et al. Expiration: August 1996 [Page 3] 4]

Internet Draft RSVP Specification February 1996

1. Introduction

This document defines RSVP, a resource reservation setup protocol
designed for an integrated services Internet [RSVP93,ISInt93].

The RSVP protocol is used by a host, on behalf of an application data
stream, to request a specific quality of service (QoS) from the
network. The RSVP protocol is also used by routers to deliver QoS
requests to all nodes along the path(s) of the data stream and to
establish and maintain state to provide the requested service. RSVP
requests will generally, although not necessarily, result in
resources being reserved along the data path.

RSVP requests resources for simplex data streams, i.e., it requests
resources in only one direction. Therefore, RSVP treats a sender as
logically distinct from a receiver, although the same application
process may act as both a sender and a receiver at the same time.
RSVP operates on top of IP (either IPv4 or IP6), occupying the place
of a transport protocol in the protocol stack. However, RSVP does
not transport application data but is rather an Internet control
protocol, like ICMP, IGMP, or routing protocols. Like the
implementations of routing and management protocols, an
implementation of RSVP will typically execute in the background, not
in the data forwarding path, as shown in Figure 1.

RSVP is not itself a routing protocol; RSVP is designed to operate
with current and future unicast and multicast routing protocols. An
RSVP daemon consults the local routing database(s) to obtain routes.
In the multicast case, for example, a host sends IGMP messages to
join a multicast group and then sends RSVP messages to reserve
resources along the delivery path(s) of that group. Routing
protocols determine where packets get forwarded; RSVP is only
concerned with the QoS of those packets that are forwarded in
accordance with routing.

Braden, Zhang, et al. Expiration: August 1996 [Page 4] 5]

Internet Draft RSVP Specification February 1996

HOST ROUTER

_________________________ RSVP _____________________________
| | .--------------. |
| _______ ______ | / | ________ . ______ |
| | | | | | / || | . | | | RSVP
| |Applic-| | RSVP <----/ ||Routing | -> RSVP <---------->
| | App <----->daemon| | ||Protocol| |daemon| _____ |
| | | | | | || daemon <----> >|Polcy||
| |_______| |___.__| | ||_ ._____| |__.__.||Cntrl||
| | | | | | | .|_____||
|===|===============|=====| |===|=============|====.======|
| data .........| | | | ...........| .____ |
| | ____V_ ____V____ | | _V__V_ _____V___ |Admis||
| | |Class-| | || data | |Class-| | ||Cntrl||
| |=> ifier|=> Packet ============> ifier|==> Packet ||_____|| data
| |______| |Scheduler|| | |______| |Scheduler|===========>
| |_________|| | |_________| |
|_________________________| |_____________________________|

Figure 1: RSVP in Hosts and Routers

Each node that is capable of resource reservation passes incoming
data packets through a "packet classifier", which determines the
route and the QoS class for each packet. For each outgoing
interface, a " packet scheduler" then makes forwarding decisions for
each packet to achieve the promised QoS on the particular link-layer
medium used by that interface.

If the link-layer medium is QoS-active, i.e., if it has its own QoS
management capability, then the packet scheduler is responsible for
negotiation with the link layer to obtain the QoS requested by RSVP.
This mapping to the link layer QoS may be accomplished in a number of
possible ways; the details will be medium-dependent. On a QoS-
passive medium such as a leased line, the scheduler itself allocates
packet transmission capacity. The scheduler may also allocate other
system resources such as CPU time or buffers.

In order to efficiently accommodate heterogeneous receivers and
dynamic group membership, RSVP makes receivers responsible for
requesting QoS [RSVP93]. A QoS request, which typically originates
from a receiver host application, is passed to the local RSVP
implementation, shown as a daemon process in Figure 1. The RSVP
protocol then carries the request to all the nodes (routers and
hosts) along the reverse data path(s) to the data source(s).

Braden, Zhang, et al. Expiration: August 1996 [Page 5] 6]

Internet Draft RSVP Specification February 1996

At each node, the RSVP daemon communicates with two local decision
modules, "admission control" and "policy control". Admission control
determines whether the node has sufficient available resources to
supply the requested QoS. Policy control determines whether the user
has administrative permission to make the reservation. If both
checks succeeds, the RSVP daemon sets parameters in the packet
classifier and scheduler to obtain the desired QoS. If either check
fails, the RSVP program returns an error notification to the
application process that originated the request. We refer to the
packet classifier, packet scheduler, and admission control components
as "traffic control".

RSVP is designed to scale well for very large multicast groups.
Since both the membership of a large group and the topology of large
multicast trees are likely to change with time, the RSVP design
assumes that router state for traffic control will be built and
destroyed incrementally. For this purpose, RSVP uses "soft state" in
the routers. That is, RSVP sends periodic refresh messages to
maintain the state along the reserved path(s); in absence of
refreshes, the state will automatically time out and be deleted.

RSVP protocol mechanisms provide a general facility for creating and
maintaining distributed reservation state across a mesh of multicast
or unicast delivery paths. RSVP transfers reservation parameters as
opaque data (except for certain well-defined operations on the data),
which it simply passes to traffic control for interpretation.
Although the RSVP protocol mechanisms are largely independent of the
encoding of these parameters, the encodings must be defined in the
reservation model that is presented to an application; see Appendix A
for more details.

In summary, RSVP has the following attributes:

o RSVP makes resource reservations for both unicast and many-to-
many multicast applications, adapting dynamically to changing
group membership as well as changing routes.

o RSVP is simplex, i.e., it reserves for a data flow in one
direction only.

o RSVP is receiver-oriented, i.e., the receiver of a data flow
initiates and maintains the resource reservation used for that
flow.

o RSVP maintains "soft state" in the routers, providing graceful
support for dynamic membership changes and automatic adaptation
to routing changes.

Braden, Zhang, et al. Expiration: August 1996 [Page 6] 7]

Internet Draft RSVP Specification February 1996

o RSVP provides several reservation models or "styles" (defined
below) to fit a variety of applications.

o RSVP provides transparent operation through routers that do not
support it.

Further discussion on the objectives and general justification for
RSVP design are presented in [RSVP93,ISInt93].

The remainder of this section describes the RSVP reservation
services. Section 2 presents an overview of the RSVP protocol
mechanisms. Section 3 contains the functional specification of RSVP,
while Section 4 presents explicit message processing rules. Appendix
A defines the variable-length typed data objects used in the RSVP
protocol. Appendix B defines error codes and values. Appendix C
defines an extension for UDP encapsulation of RSVP messages.
Finally, some experimental RSVP features are documented in Appendix D
for future reference.

1.1 Data Flows

RSVP defines a "session" as a data flow with a particular
destination and transport-layer protocol. The destination of a
session is generally defined by DestAddress, the IP destination
address of the data packets, and perhaps by DstPort, a
"generalized destination port", i.e., some further demultiplexing
point in the transport or application protocol layer. RSVP treats
each session independently, and this document often assumes the
qualification "for the same session".

DestAddress is a group address for multicast delivery or the
unicast address of a single receiver. DstPort could be defined by
a UDP/TCP destination port field, by an equivalent field in
another transport protocol, or by some application-specific
information. Although the RSVP protocol is designed to be easily
extensible for greater generality, the present version supports
only UDP/TCP ports as generalized ports.

Note that it is not strictly necessary to include ports in the
session definition when DestAddress is multicast, since different
sessions can always have different multicast addresses. However,
destination ports are necessary to allow more than one unicast
session to the same receiver host.

Figure 2 illustrates the flow of data packets in a single RSVP
session, assuming multicast data distribution. The arrows
indicate data flowing from senders S1 and S2 to receivers R1, R2,
and R3, and the cloud represents the distribution mesh created by

Braden, Zhang, et al. Expiration: August 1996 [Page 7] 8]

Internet Draft RSVP Specification February 1996

multicast routing. Multicast distribution forwards a copy of each
data packet from a sender Si to every receiver Rj; a unicast
distribution session has a single receiver R. Each sender Si may
be running in a unique Internet host, or a single host may contain
multiple senders, distinguished by generalized source ports.

Senders Receivers
_____________________
( ) ===> R1
S1 ===> ( Multicast )
( ) ===> R2
( distribution )
S2 ===> ( )
( by Internet ) ===> R3
(_____________________)

Figure 2: Multicast Distribution Session

For unicast transmission, there will be a single destination host
but there may be multiple senders; RSVP can set up reservations
for multipoint-to-single-point transmission.

1.2 Reservation Model

An elementary RSVP reservation request consists of a "flowspec"
together with a "filter spec"; this pair is called a "flow
descriptor". The flowspec specifies a desired QoS. The filter
spec, together with a session specification, defines the set of
data packets -- the "flow" -- to receive the QoS defined by the
flowspec. The flowspec is used to set parameters to the node's
packet scheduler (assuming that admission control succeeds), while
the filter spec is used to set parameters in the packet
classifier. Data packets that are addressed to a particular
session but do not match any of the filter specs for that session
are handled as best-effort traffic.

Note that the action to control QoS occurs at the place where the
data enters the medium, i.e., at the upstream end of the link,
although an RSVP reservation request originates from receiver(s)
downstream. In this document, we define the directional terms
"upstream" vs. "downstream", "previous hop" vs. "next hop", and
"incoming interface" vs "outgoing interface" with respect to the
direction of data flow.

The flowspec in a reservation request will generally include a

Braden, Zhang, et al. Expiration: August 1996 [Page 8] 9]

Internet Draft RSVP Specification February 1996

service class and two sets of numeric parameters: (1) an "Rspec"
(R for `reserve') that defines the desired QoS, and (2) a "Tspec"
(T for `traffic') that describes the data flow. The formats and
contents of Tspecs and Rspecs are determined by the integrated
service model [ServTempl95a], and are generally opaque to RSVP.

In the most general approach [RSVP93], filter specs may select
arbitrary subsets of the packets in a given session. Such subsets
might be defined in terms of senders (i.e., sender IP address and
generalized source port), in terms of a higher-level protocol, or
generally in terms of any fields in any protocol headers in the
packet. For example, filter specs might be used to select
different subflows in a hierarchically-encoded signal by selecting
on fields in an application-layer header. In the interest of
simplicity (and to minimize layer violation), the present RSVP
version uses a much more restricted form of filter spec,
consisting of sender IP address and optionally the UDP/TCP port
number SrcPort.

Because the UDP/TCP port numbers are used for packet
classification, each router must be able to examine these fields.
As a result, it is generally necessary to avoid IP fragmentation
of a data stream for which a resource reservation is desired.

RSVP reservation request messages originate at receivers and are
passed upstream towards the sender(s). At each intermediate node,
two general actions are taken on the request.

1. Make a reservation

The request is passed to admission control and policy
control. If either test fails, the reservation is rejected
and RSVP returns an error message to the appropriate
receiver(s). If both succeed, the node uses the flowspec to
set up the packet scheduler for the desired QoS and the
filter spec to set the packet classifier to select the
appropriate data packets.

2. Forward the request upstream

The reservation request is propagated upstream towards the
appropriate senders. The set of sender hosts to which a
given reservation request is propagated is called the "scope"
of that request.

The reservation request that a node forwards upstream may differ
from the request that it received from downstream, for two
reasons. First, it is possible in theory for the traffic control

Braden, Zhang, et al. Expiration: August 1996 [Page 9] 10]

Internet Draft RSVP Specification February 1996

mechanism to modify the flowspec hop-by-hop, although none of the
currently defined services does so. Second, reservations for the
same sender, or the same set of senders, from different downstream
branches of the multicast tree(s) are "merged" as reservations
travel upstream; a node forwards upstream only the reservation
request with the "maximum" flowspec.

When a receiver originates a reservation request, it can also
request a confirmation message to indicate that its request was
(probably) installed in the network. A successful reservation
request propagates upstream along the multicast tree until it
reaches a point where an existing reservation is equal or greater
than that being requested. At that point, the arriving request is
merged with the reservation in place, and need not be forwarded
further, and the node may then send a reservation confirmation
message back to the receiver. Note that the receipt of a
confirmation is only a high-probability indication, not a
guarantee, that the requested service is in place all the way to
the sender(s), as explained in Section 2.7.

The basic RSVP reservation model is "one pass": a receiver sends a
reservation request upstream, and each node in the path either
accepts or rejects the request. This scheme provides no easy way
for a receiver to find out the resulting end-to-end service.
Therefore, RSVP supports an enhancement to one-pass service known
as "One Pass With Advertising" (OPWA) [Shenker94]. With OPWA,
RSVP control packets are sent downstream, following the data
paths, to gather information that may be used to predict the end-
to-end QoS. The results ("advertisements") are delivered by RSVP
to the receiver hosts and perhaps to the receiver applications.
The advertisements may then be used by the receiver to construct,
or to dynamically adjust, an appropriate reservation request.

1.3 Reservation Styles

A reservation request includes a set of options, which are
collectively called the reservation "style".

One reservation option concerns the treatment of reservations for
different senders within the same session: establish a "distinct"
reservation for each upstream sender, or else make a single
reservation that is "shared" among all packets of selected
senders.

Another reservation option controls the selection of senders: an "
explicit" list of all selected senders, or a "wildcard" that
implicitly selects all the senders to the session. In an explicit
sender-selection reservation, each filter spec must match exactly

Braden, Zhang, et al. Expiration: August 1996 [Page 10] 11]

Internet Draft RSVP Specification February 1996

one sender, while in a wildcard sender-selection no filter spec is
needed.

Sender || Reservations:
Selection || Distinct | Shared
_________||__________________|____________________
|| | |
Explicit || Fixed-Filter | Shared-Explicit |
|| (FF) style | (SE) Style |
__________||__________________|____________________|
|| | |
Wildcard || (None defined) | Wildcard-Filter |
|| | (WF) Style |
__________||__________________|____________________|

Figure 3: Reservation Attributes and Styles

The styles currently defined are as follows (see Figure 3):

o Wildcard-Filter (WF) Style

The WF style implies the options: "shared" reservation and "
wildcard" sender selection. Thus, a WF-style reservation
creates a single reservation into which flows from all
upstream senders are mixed. This reservation may be thought
of as a shared "pipe", whose "size" is the largest of the
resource requests from all receivers, independent of the
number of senders using it. A WF-style reservation is
propagated upstream towards all sender hosts, and
automatically extends to new senders as they appear.

Symbolically, we can represent a WF-style reservation request
by:

WF( * {Q})

where the asterisk represents wildcard sender selection and Q
represents the flowspec.

o Fixed-Filter (FF) Style

The FF style implies the options: "distinct" reservations and
"explicit" sender selection. Thus, an elementary FF-style

Braden, Zhang, et al. Expiration: August 1996 [Page 11] 12]

Internet Draft RSVP Specification February 1996

reservation request creates a distinct reservation for data
packets from a particular sender, not sharing them with other
senders' packets for the same session.

The total reservation on a link for a given session is the
total of the FF reservations for all requested senders. On
the other hand, FF reservations requested by different
receivers Rj but selecting the same sender Si must be merged
to share a single reservation.

Symbolically, we can represent an elementary FF reservation
request by:

FF( S{Q})

where S is the selected sender and Q is the corresponding
flowspec; the pair forms a flow descriptor. RSVP allows
multiple elementary FF-style reservations to be requested at
the same time, using a list of flow descriptors:

FF( S1{Q1}, S2{Q2}, ...)

o Shared Explicit (SE) Style

The SE style implies the options: "shared" reservation and "
explicit" sender selection. Thus, an SE-style reservation
creates a single reservation into which flows from all
upstream senders are mixed. However, like the FF style, the
SE style allows a receiver to explicitly specify the set of
senders.

Symbolically, we

We can represent an SE reservation request by:

SE( (S1,S2,...){Q} ),

i.e., a flow descriptor composed of containing a
flowspec Q and a list of senders S1, S2, etc. ... by:

SE( (S1,S2,...){Q} )

Both WF and SE styles create shared reservations, appropriate for
those multicast applications whose properties make it unlikely
that multiple data sources will transmit simultaneously.
Packetized audio is an example of an application suitable for
shared reservations; since a limited number of people talk at
once, each receiver might issue a WF or SE reservation request for
twice the bandwidth required for one sender (to allow some over-

Braden, Zhang, et al. Expiration: August 1996 [Page 12]

Internet Draft RSVP Specification February 1996
speaking). On the other hand, the FF style, which creates
independent reservations for the flows from different senders, is

Braden, Zhang, et al. Expiration: August 1996 [Page 13]

Internet Draft RSVP Specification February 1996

appropriate for video signals.

The RSVP rules disallow merging of shared reservations with
distinct reservations, since these modes are fundamentally
incompatible. They also disallow merging explicit sender
selection with wildcard sender selection, since this might produce
an unexpected service for a receiver that specified explicit
selection. As a result of these prohibitions, WF, SE, and FF
styles are all mutually incompatible.

It would seem possible to simulate the effect of a WF reservation
using the SE style. When an application asked for WF, the RSVP
daemon on the receiver host could use local path state to create
an equivalent SE reservation that explicitly listed all senders.
However, an SE reservation forces the packet classifier in each
node to explicitly select each sender in the list, while a WF
allows the packet classifier to simply "wild card" the sender
address and port. When there is a large list of senders, a WF
style reservation can therefore result in considerably less
overhead than an equivalent SE style reservation. For this
reason, both SE and WF are included in the protocol.

Other reservation options and styles may be defined in the future.

1.4 Examples of Styles

This section presents examples of each of the reservation styles
and shows the effects of merging.

Figure 4 illustrates a router with two incoming interfaces through
which data streams will arrive, labeled (a) and (b), and two
outgoing interfaces through which data will be forwarded, labeled
(c) and (d). This topology will be assumed in the examples that
follow. There are three upstream senders; packets from sender S1
(S2 and S3) arrive through previous hop (a) ((b), respectively).
There are also three downstream receivers; packets bound for R1
(R2 and R3) are routed via outgoing interface (c) ((d),
respectively). We furthermore assume that R2 and R3 arrive via
different next hops, e.g., via the two routers D and D' in Figure
9. This illustrates the effect of a non-RSVP cloud or a broadcast
LAN on interface (d).

In addition to the connectivity shown in 4, we must also specify
the multicast routes within this node. Assume first that data
packets from each Si shown in Figure 4 is routed to both outgoing
interfaces. Under this assumption, Figures 5, 6, and 7 illustrate
Wildcard-Filter, Fixed-Filter, and Shared-Explicit reservations,
respectively.

Braden, Zhang, et al. Expiration: August 1996 [Page 13] 14]

Internet Draft RSVP Specification February 1996

Wildcard-Filter, Fixed-Filter, and Shared-Explicit reservations,
respectively.

________________
(a)| | (c)
( S1 ) ---------->| |----------> ( R1 )
| Router |
(b)| | (d)
( S2,S3 ) ------->| |----------> ( R2, R3 )
|________________|

Figure 4: Router Configuration

For simplicity, these examples show flowspecs as one-dimensional
multiples of some base resource quantity B. The "Receive" column
shows the RSVP reservation requests received over outgoing
interfaces (c) and (d), and the "Reserve" column shows the
resulting reservation state for each interface. The "Send"
column shows the reservation requests that are sent upstream to
previous hops (a) and (b). In the "Reserve" column, each box
represents one reserved "pipe" on the outgoing link, with the
corresponding flow descriptor.

Figure 5, showing the WF style, illustrates the two possible
merging situations. Each of the two next hops on interface (d)
results in a separate RSVP reservation request, as shown. These
two requests are merged into the effective flowspec 3B, which is
used to make the reservation on interface (d). To forward the
reservation requests upstream, the reservations on the interfaces
(c) and (d) are merged; as a result, the larger flowspec 4B is
forwarded upstream to each previous hop.

Braden, Zhang, et al. Expiration: August 1996 [Page 14]

Internet Draft RSVP Specification February 1996

|
Send | Reserve Receive
|
| _______
WF( *{4B} ) <- (a) | (c) | * {4B}| (c) <- WF( *{4B} )
| |_______|
|
-----------------------|----------------------------------------
| _______
WF( *{4B} ) <- (b) | (d) | * {3B}| (d) <- WF( *{3B} )
| |_______| <- WF( *{2B} )

Figure 5: Wildcard-Filter (WF) Reservation Example

Braden, Zhang, et al. Expiration: August 1996 [Page 15]

Internet Draft RSVP Specification February 1996

Figure 6 shows Fixed-Filter (FF) style reservations. The flow
descriptors for senders S2 and S3, received from outgoing
interfaces (c) and (d), are packed into the request forwarded to
previous hop (b). On the other hand, the three different flow
descriptors for sender S1 are merged into the single request FF(
S1{4B} ), which is sent to previous hop (a). For each outgoing
interface, there is a separate reservation for each source that
has been requested, but this reservation is shared among all the
receivers that made the request.

|
Send | Reserve Receive
|
| ________
FF( S1{4B} ) <- (a) | (c) | S1{4B} | (c) <- FF( S1{4B}, S2{5B} )
| |________|
| | S2{5B} |
| |________|
---------------------|---------------------------------------------
| ________
<- (b) | (d) | S1{3B} | (d) <- FF( S1{3B}, S3{B} )
FF( S2{5B}, S3{B} ) | |________| <- FF( S1{B} )
| | S3{B} |
| |________|

Figure 6: Fixed-Filter (FF) Reservation Example

Figure 7 shows an example of Shared-Explicit (SE) style

Braden, Zhang, et al. Expiration: August 1996 [Page 15]

Internet Draft RSVP Specification February 1996
reservations. When SE-style reservations are merged, the
resulting filter spec is the union of the original filter specs.

Braden, Zhang, et al. Expiration: August 1996 [Page 16]

Internet Draft RSVP Specification February 1996

|
Send | Reserve Receive
|
| ________
SE( S1{3B} ) <- (a) | (c) |(S1,S2) | (c) <- SE( (S1,S2){B} )
| | {B} |
| |________|
---------------------|---------------------------------------------
| __________
<- (b) | (d) |(S1,S2,S3)| (d) <- SE( (S1,S3){3B} )
SE( (S2,S3){3B} ) | | {3B} | <- SE( S2{2B} )
| |__________|

Figure 7: Shared-Explicit (SE) Reservation Example

The three examples just shown assume that data packets from S1,
S2, and S3 are routed to both outgoing interfaces. The top part
of Figure 8 shows another routing assumption: data packets from S2
and S3 are not forwarded to interface (c), e.g., because the
network topology provides a shorter path for these senders towards
R1, not traversing this node. The bottom part of Figure 8 shows
WF style reservations under this assumption. Since there is no
route from (b) to (c), the reservation forwarded out interface (b)
considers only the reservation on interface (d).

Braden, Zhang, et al. Expiration: August 1996 [Page 16] 17]

Internet Draft RSVP Specification February 1996

_______________
(a)| | (c)
( S1 ) ---------->| >-----------> |----------> ( R1 )
| - |
| - |
(b)| - | (d)
( S2,S3 ) ------->| >-------->--> |----------> ( R2, R3 )
|_______________|

Router Configuration

|
Send | Reserve Receive
|
| _______
WF( *{4B} ) <- (a) | (c) | * {4B}| (c) <- WF( *{4B} )
| |_______|
|
-----------------------|----------------------------------------
| _______
WF( *{3B} ) <- (b) | (d) | * {3B}| (d) <- WF( * {3B} )
| |_______| <- WF( * {2B}

Figure 8: WF Reservation Example -- Partial Routing

Braden, Zhang, et al. Expiration: August 1996 [Page 17] 18]

Internet Draft RSVP Specification February 1996

2. RSVP Protocol Mechanisms

2.1 RSVP Messages

Previous Incoming Outgoing Next
Hops Interfaces Interfaces Hops

_____ _____________________ _____
| | data --> | | data --> | |
| A |-----------| a c |--------------| C |
|_____| Path --> | | Path --> |_____|
<-- Resv | | <-- Resv _____
_____ | ROUTER | | | |
| | | | | |--| D |
| B |--| data-->| | data --> | |_____|
|_____| |--------| b d |-----------|
| Path-->| | Path --> | _____
_____ | <--Resv|_____________________| <-- Resv | | |
| | | |--| D' |
| B' |--| | |_____|
|_____| | |

Figure 9: Router Using RSVP

Figure 9 illustrates RSVP's model of a router node. Each data
stream arrives from a "previous hop" through a corresponding
"incoming interface" and departs through one or more "outgoing
interface"(s). The same physical interface may act in both the
incoming and outgoing roles for different data flows in the same
session. Multiple previous hops and/or next hops may be reached
through a given physical interface, as a result of the connected
network being a shared medium, or the existence of non-RSVP
routers in the path to the next RSVP hop (see Section 2.9). An
RSVP daemon preserves the next and previous hop addresses in its
reservation and path state, respectively.

There are two fundamental RSVP message types: RESV Resv and PATH. Path.

Each receiver host sends RSVP reservation request (RESV) (Resv) messages
upstream towards the senders. These reservation messages must
follow exactly the reverse of the routes the data packets will
use, upstream to all the sender hosts included in the sender
selection. RESV Resv messages are delivered to the sender hosts
themselves so that the hosts can set up appropriate traffic
control parameters for the first hop.

Braden, Zhang, et al. Expiration: August 1996 [Page 18] 19]

Internet Draft RSVP Specification February 1996

Each RSVP sender host transmits RSVP PATH Path messages downstream
along the uni-/multicast routes provided by the routing
protocol(s), following the paths of the data. These "Path"
messages store "path state" in each node along the way. This path
state includes at least the unicast IP address of the previous hop
node, which is used to route the RESV Resv messages hop-by-hop in the
reverse direction. (In the future, some routing protocols may
supply reverse path forwarding information directly, replacing the
reverse-routing function of path state).

A PATH Path message may carry the following information in addition to
the previous hop address:

o Sender Template

A PATH Path message is required to carry a Sender Template, which
describes the format of data packets that the sender will
originate. This template is in the form of a filter spec
that could be used to select this sender's packets from
others in the same session on the same link.

Like a filter spec, the Sender Template is less than fully
general at present, specifying only the sender IP address and
optionally the UDP/TCP sender port. It assumes the protocol
Id specified for the session.

o Sender Tspec

A PATH Path message is required to carry a Sender Tspec, which
defines the traffic characteristics of the data stream that
the sender will generate. This Tspec is used by traffic
control to prevent over-reservation (and perhaps unnecessary
Admission Control failure) on upstream links.

o Adspec

A PATH Path message may optionally carry a package of OPWA
advertising information, known as an "Adspec". An Adspec
received in a PATH Path message is passed to the local traffic
control, which returns an updated Adspec; the updated version
is then forwarded in PATH Path messages sent downstream.

PATH

Path messages are sent with the same source and destination
addresses as the data, so that they will be routed correctly
through non-RSVP clouds (see Section 2.9). On the other hand,
RESV
Resv messages are sent hop-by-hop; each RSVP-speaking node
forwards a RESV Resv message to the unicast address of a previous RSVP
hop.

Braden, Zhang, et al. Expiration: August 1996 [Page 19] 20]

Internet Draft RSVP Specification February 1996

2.2 Port Usage

At present an RSVP session is defined by the triple: (DestAddress,
ProtocolId, DstPort). Here DstPort is a UDP/TCP destination port
field (i.e., a 16-bit quantity carried at octet offset +2 in the
transport header). DstPort may be omitted (set to zero) if the
ProtocolId specifies a protocol that does not have a destination
port field in the format used by UDP and TCP.

RSVP allows any value for ProtocolId. However, end-system
implementations of RSVP may know about certain values for this
field, and in particular must know about the values for UDP and
TCP (17 and 6, respectively). An end system should give an error
to an application that either:

o specifies a non-zero DstPort for a protocol that does not
have UDP/TCP-like ports, or

o specifies a zero DstPort for a protocol that does have
UDP/TCP-like ports.

Filter specs and sender templates specify the pair: (SrcAddress,
SrcPort), where SrcPort is a UDP/TCP source port field (i.e., a
16-bit quantity carried at octet offset +0 in the transport
header). SrcPort may be omitted (set to zero) in certain cases.

The following rules hold for the use of zero DstPort and/or
SrcPort fields in RSVP.

1. Destination ports must be consistent.

Path state and/or reservation state for the same DestAddress
and ProtocolId must have DstPort values that are all zero or
all non-zero. Violation of this condition in a node is a
"Conflicting Dest Port" error.

2. Destination ports rule.

If DstPort in a session definition is zero, all SrcPort
fields used for that session must also be zero. The
assumption here is that the protocol does not have UDP/TCP-
like ports. Violation of this condition in a node is a
"Conflicting Src Port" error.

3. Source Ports must be consistent.

A sender host must not send path state both with and without
a zero SrcPort. Violation of this condition is an "Ambiguous

Braden, Zhang, et al. Expiration: August 1996 [Page 20] 21]

Internet Draft RSVP Specification February 1996

Path" error.

2.3 Merging Flowspecs

As noted earlier, a single physical interface may receive multiple
reservation requests from different next hops for the same session
and with the same filter spec, but RSVP should install only one
reservation on that interface. The installed reservation should
have an effective flowspec that is the "largest" of the flowspecs
requested by the different next hops. Similarly, a RESV Resv message
forwarded to a previous hop should carry a flowspec that is the
"largest" of the flowspecs requested by the different next hops
(however, in certain cases the "smallest" is taken rather than the
largest, see Section 3.4). These cases all represent flowspec
merging.

Flowspec merging requires calculation of the "largest" of a set of
flowspecs. However, since flowspecs are generally multi-
dimensional vectors (they may contain both Tspec and Rspec
components, each of which may itself be multi-dimensional), it may
not be possible to strictly order two flowspecs. For example, if
one request calls for a higher bandwidth and another calls for a
tighter delay bound, one is not "larger" than the other. In such
a case, instead of taking the larger, RSVP must compute and use a
third flowspec that is at least as large as each. Mathematically,
RSVP merges flowspecs using the " least upper bound" (LUB) instead
of the maximum. Typically, the LUB is calculated by creating a
new flowspec whose components are individually either the max or
the min of corresponding components of the flowspecs being merged.
For example, the LUB of Tspecs defined by token bucket parameters
is computed by taking the maximums of the bucket size and the rate
parameters. In several cases, the GLB (Greatest Lower Bound) is
used instead of the LUB; this simply interchanges max and min
operations.

We can now give the complete rules for calculating the effective
flowspec (Te, Re) to be installed on an interface. Here Te is the
effective Tspec and Re is the effective Rspec. As an example,
consider interface (d) in Figure 9.

1. Re is calculated as the largest (using an LUB if necessary)
of the Rspecs in RESV Resv messages from different next hops
(e.g., D and D') but the same outgoing interface (d).

2. All Tspecs that were supplied in PATH Path messages from different
previous hops (e.g., some or all of A, B, and B' in Figure 9)
are summed; call this sum Path_Te.

Braden, Zhang, et al. Expiration: August 1996 [Page 21] 22]

Internet Draft RSVP Specification February 1996

3. The maximum Tspec supplied in RESV Resv messages from different
next hops (e.g., D and D') is calculated; call this Resv_Te.

4. Te is the GLB (greatest lower bound) of Path_Te and Resv_Te.

Flowspecs, Tspecs, and Adspecs are opaque to RSVP. Therefore, the
last of these steps is actually performed by traffic control. The
definition and implementation of the rules for comparing
flowspecs, calculating LUBs and GLBs, and summing Tspecs are
outside the definition of RSVP [ServTempl95a]. Section 3.10.4
shows generic calls that an RSVP daemon could use for these
functions.

2.4 Soft State

RSVP takes a "soft state" approach to managing the reservation
state in routers and hosts. RSVP soft state is created and
periodically refreshed by PATH Path and RESV Resv messages. The state is
deleted if no matching refresh messages arrive before the
expiration of a "cleanup timeout" interval. State may also be
deleted by an explicit "teardown" message, described in the next
section. At the expiration of each "refresh timeout" period and
after a state change, RSVP scans its state to build and forward
PATH
Path and RESV Resv refresh messages to succeeding hops.

PATH

Path and RESV Resv messages are idempotent. When a route changes, the
next PATH Path message will initialize the path state on the new route,
and future RESV Resv messages will establish reservation state there;
the state on the now-unused segment of the route will time out.
Thus, whether a message is "new" or a "refresh" is determined
separately at each node, depending upon the existing state at that
node.

RSVP sends its messages as IP datagrams with no reliability
enhancement. Periodic transmission of refresh messages by hosts
and routers is expected to handle the occasional loss of an RSVP
message. If the effective cleanup timeout is set to K times the
refresh timeout period, then RSVP can tolerate K-1 successive RSVP
packet losses without falsely erasing a reservation. We recommend
that the network traffic control mechanism be statically
configured to grant some minimal bandwidth for RSVP messages to
protect them from congestion losses.

The state maintained by RSVP is dynamic; to change the set of
senders Si or to change any QoS request, a host simply starts
sending revised PATH Path and/or RESV Resv messages. The result will be an
appropriate adjustment in the RSVP state in all nodes along the
path.

Braden, Zhang, et al. Expiration: August 1996 [Page 22] 23]

Internet Draft RSVP Specification February 1996

In steady state, refreshing is performed hop-by-hop, to allow
merging. When the received state differs from the stored state,
the stored state is updated. If this update results in
modification of state to be forwarded in refresh messages, these
refresh messages must be generated and forwarded immediately, so
that state changes can be propagated end-to-end without delay.
However, propagation of a change stops when and if it reaches a
point where merging causes no resulting state change. This
minimizes RSVP control traffic due to changes and is essential for
scaling to large multicast groups.

State that is received through a particular interface I* should
never be forwarded out the same interface. Conversely, state that
is forwarded out interface I* must be computed using only state
that arrived on interfaces different from I*. A trivial example
of this rule is illustrated in Figure 10, which shows a transit
router with one sender and one receiver on each interface (and
assumes one next/previous hop per interface). Interfaces (a) and
(c) serve as both outgoing and incoming interfaces for this
session. Both receivers are making wildcard-scope reservations,
in which the RESV Resv messages are forwarded to all previous hops for
senders in the group, with the exception of the next hop from
which they came. The result is independent reservations in the
two directions.

There is an additional rule governing the forwarding of RESV Resv
messages: state from RESV messages received from outgoing
interface Io should be forwarded to incoming interface Ii only if
PATH
Path messages from Ii are forwarded to Io.

Braden, Zhang, et al. Expiration: August 1996 [Page 23] 24]

Internet Draft RSVP Specification February 1996

________________
a | | c
( R1, S1 ) <----->| Router |<-----> ( R2, S2 )
|________________|

Send | Receive
|
WF( *{3B}) <-- (a) | (c) <-- WF( *{3B})
|
Receive | Send
|
WF( *{4B}) --> (a) | (c) --> WF( *{4B})
|
Reserve on (a) | Reserve on (c)
__________ | __________
| * {4B} | | | * {3B} |
|__________| | |__________|
|

Figure 10: Independent Reservations

2.5 Teardown

Upon arrival, RSVP "teardown" messages remove path and reservation
state immediately. Although it is not necessary to explicitly
tear down an old reservation, we recommend that all end hosts send
a teardown request as soon as an application finishes.

There are two types of RSVP teardown message, PTEAR PathTear and RTEAR.
ResvTear. A
PTEAR PathTear message travels towards all receivers
downstream from its point of initiation and deletes path state, as
well as all dependent reservation state, along the way. An RTEAR
ResvTear message deletes reservation state and travels towards all
senders upstream from its point of initiation. A PTEAR (RTEAR) PathTear
(ResvTear) message may be conceptualized as a reversed-sense Path
message (Resv message, respectively).

A teardown request may be initiated either by an application in an
end system (sender or receiver), or by a router as the result of
state timeout. Once initiated, a teardown request must be
forwarded hop-by-hop without delay. A teardown message deletes
the specified state in the node where it is received. As always,
this state change will be propagated immediately to the next node,
but only if there will be a net change after merging. As a
result, an RTEAR ResvTear message will prune the reservation state back
(only) as far as possible.

Braden, Zhang, et al. Expiration: August 1996 [Page 24] 25]

Internet Draft RSVP Specification February 1996

Like all other RSVP messages, teardown requests are not delivered
reliably. The loss of a teardown request message will not cause a
protocol failure because the unused state will eventually time out
even though it is not explicitly deleted. If a teardown message
is lost, the router that failed to receive that message will time
out its state and initiate a new teardown message beyond the loss
point. Assuming that RSVP message loss probability is small, the
longest time to delete state will seldom exceed one refresh
timeout period.

2.6 Errors

There are two RSVP error messages, RERR ResvErr and PERR. PathErr. PERR
messages are very simple. They are simply sent upstream to the
sender that created the error, and they do not change path state
in the nodes though which they pass. There are only a few
possible causes of path errors.

However, there are a number of ways for a syntactically valid
reservation request to fail at some node along the path, for
example:

1. The effective flowspec that is computed using the new request
may fail admission control.

2. Administrative policy may prevent the requested reservation.

3. There may be no matching path state, so that the request
cannot be forwarded towards the sender(s).

4. A reservation style that requires the explicit selection of a
unique sender may have a filter spec that is ambiguous, i.e.,
that matches more than one sender in the path state, due to
the use of wildcard fields in the filter spec.

5. The requested style may be incompatible with the style(s) of
existing reservations. The incompatibility may occur among
reservations for the same session on the same outgoing
interface, or among effective reservations on different
outgoing interfaces.

A node may also decide to preempt an established reservation.

The handling of RERR ResvErr messages is somewhat complex (Section
3.4). Since a request that fails may be the result of merging a
number of requests, a reservation error must be reported to all of
the responsible receivers. In addition, merging heterogeneous
requests creates a potential difficulty known as the "killer

Braden, Zhang, et al. Expiration: August 1996 [Page 25] 26]

Internet Draft RSVP Specification February 1996

reservation" problem, in which one request could deny service to
another. There are actually two killer-reservation problems.

1. The first killer reservation problem (KR-I) arises when there
is already a reservation Q0 in place. If another receiver
now makes a larger reservation Q1 > Q0, the result of merging
Q0 and Q1 may be rejected by admission control in some
upstream node. This must not deny service to Q0.

The solution to this problem is simple: when admission
control fails for a reservation request, any existing
reservation is left in place.

2. The second killer reservation problem (KR-II) is the
converse: the receiver making a reservation Q1 is persistent
even though Admission Control is failing for Q1 in some node.
This must not prevent a different receiver from now
establishing a smaller reservation Q0 that will succeed.

To solve this problem, a RERR ResvErr message establishes
additional state, called "blockade state", in each node
through which it passes. Blockade state in a node modifies
the merging procedure to omit the offending flowspec (Q1 in
the example) from the merge, allowing a smaller request to be
forwarded and established. The Q1 reservation state is said
to be "blockaded". Detailed rules are presented in Section
3.4.

A reservation request that fails Admission Control creates
blockade state but is left in place in nodes downstream of the
failure point. It has been suggested that these reservations
downstream from the failure represent "wasted" reservations and
should be timed out if not actively deleted. However, in general
the downstream reservations will not be "wasted".

o There are two possible reasons for a receiver persisting in a
failed reservation: (1) it is polling for resource
availability along the entire path, or (2) it wants to obtain
the desired QoS along as much of the path as possible.
Certainly in the second case, and perhaps in the first case,
the receiver will want to hold onto the reservations it has
made downstream from the failure.

o If these downstream reservations were not retained, the
responsiveness of RSVP to certain transient failures would be
impaired. For example, suppose a route "flaps" to an
alternate route that is congested, so an existing reservation
suddenly fails, then quickly recovers to the original route.
The blockade state in each downstream router must not remove

Braden, Zhang, et al. Expiration: August 1996 [Page 26] 27]

Internet Draft RSVP Specification February 1996

The blockade state in each downstream router must not remove
the state or prevent its immediate refresh.

o If we did not refresh the downstream reservations, they might
time out, to be restored every Td seconds. Such on/off
behavior might be very distressing for users.

2.7 Confirmation

To request a confirmation for its reservation request, a receiver
Rj includes in the RESV Resv message a confirmation-request object
containing Rj's IP address. At each merge point, only the largest
flowspec and any accompanying confirmation-request object is
forwarded upstream. If the reservation request from Rj is equal
to or smaller than the reservation in place on a node, its RESV Resv
are not forwarded further, and if the RESV Resv included a
confirmation-request object, a RACK ResvConf message is sent back to
Rj. This mechanism has the following consequences:

o A new reservation request with a flowspec larger than any in
place for a session will normally result in either a RERR ResvErr
or a RACK ResvConf message back to the receiver from each sender.
In this case, the RACK ResvConf message will be an end-to-end
confirmation.

o The receipt of a RACK ResvConf gives no guarantees. Assume the
first two reservation requests from receivers R1 and R2
arrive at the node where they are merged. R2, whose
reservation was the second to arrive at that node, may
receive a RACK ResvConf from that node while R1's request has not
yet propagated all the way to a matching sender and may still
fail. Thus, R2 may receive a RACK ResvConf although there is no
end-to-end reservation in place; furthermore, R2 may receive
a RACK ResvConf followed by a RERR. ResvErr.

2.8 Policy and Security

RSVP-mediated QoS requests will result in particular user(s)
getting preferential access to network resources. To prevent
abuse, some form of back pressure on users is likely to be
required. This back pressure might take the form of
administrative rules, or of some form of real or virtual billing
for the "cost" of a reservation. The form and contents of such
back pressure is a matter of administrative policy that may be
determined independently by each administrative domain in the
Internet.

Therefore, there will be policy control as well as admission

Braden, Zhang, et al. Expiration: August 1996 [Page 27] 28]

Internet Draft RSVP Specification February 1996

Therefore, there will be policy control as well as admission
control over the establishment of reservations. As input to
policy control, RSVP messages may carry policy data. Policy data
may include credentials identifying users or user classes, account
numbers, limits, quotas, etc. Like flowspecs, policy data will be
opaque to RSVP, which will simply pass it to a "Local Policy
Module" (LPM) for a decision.

To protect the integrity of the policy control mechanisms, it may
be necessary to ensure the integrity of RSVP messages against
corruption or spoofing, hop by hop. For this purpose, RSVP
messages may carry integrity objects that can be created and
verified by neighbor RSVP-capable nodes. These objects use a
keyed cryptographic digest technique and assume that RSVP
neighbors share a secret [Baker96].

User policy data in reservation request messages presents a
scaling problem. When a multicast group has a large number of
receivers, it will be impossible or undesirable to carry all
receivers' policy data upstream to the sender(s). The policy data
will have to be administratively merged at places near the
receivers, to avoid excessive policy data. Administrative merging
implies checking the user credentials and accounting data and then
substituting a token indicating the check has succeeded. A chain
of trust established using integrity fields will allow upstream
nodes to accept these tokens.

In summary, different administrative domains in the Internet may
have different policies regarding their resource usage and
reservation. The role of RSVP is to carry policy data associated
with each reservation to the network as needed. Note that the
merge points for policy data are likely to be at the boundaries of
administrative domains. It may be necessary to carry accumulated
and unmerged policy data upstream through multiple nodes before
reaching one of these merge points.

This document does not specify the contents of policy data, the
structure of an LPM, or any generic policy models. These will be
defined in the future.

2.9 Automatic RSVP Tunneling

It is impossible to deploy RSVP (or any new protocol) at the same
moment throughout the entire Internet. Furthermore, RSVP may
never be deployed everywhere. RSVP must therefore provide correct
protocol operation even when two RSVP-capable routers are joined
by an arbitrary "cloud" of non-RSVP routers. Of course, an
intermediate cloud that does not support RSVP is unable to perform
resource reservation. However, if such a cloud has sufficient

Braden, Zhang, et al. Expiration: August 1996 [Page 28] 29]

Internet Draft RSVP Specification February 1996

resource reservation. However, if such a cloud has sufficient
capacity, it may still provide acceptable realtime service.

RSVP automatically tunnels through such a non-RSVP cloud. Both
RSVP and non-RSVP routers forward PATH Path messages towards the
destination address using their local uni-/multicast routing
table. Therefore, the routing of PATH Path messages will be unaffected
by non-RSVP routers in the path. When a PATH Path message traverses a
non-RSVP cloud, it carries to the next RSVP-capable node the IP
address of the last RSVP-capable router before entering the cloud.
This effectively constructs a tunnel through the cloud for RESV Resv
messages, which can then be forwarded directly to the next RSVP-
capable router on the path(s) back towards the source.

Even though RSVP operates correctly through a non-RSVP cloud, the
non-RSVP-capable nodes will in general perturb the QoS provided to
a receiver. Therefore, RSVP tries to inform the receiver when
there are non-RSVP-capable hops in the path to a given sender, by
means of two flag bits in the SESSION object of a PATH Path message;
see Section 3.7 and Appendix A.

Some topologies of RSVP routers and non-RSVP routers can cause
RESV
Resv messages to arrive at the wrong RSVP-capable node, or to
arrive at the wrong interface of the correct node. An RSVP daemon
must be prepared to handle either situation. If the destination
address does not match any local interface and the message is not
a PATH Path or PTEAR, PathTear, the message must be forwarded without further
processing by this node. When a RESV Resv message does arrive at the
addessed node, the IP destination address (or the LIH, defined
later) must be used to determine the interface to receive the
reservation.

2.10 Host Model

Before a session can be created, the session identification,
comprised of DestAddress and perhaps the generalized destination
port, must be assigned and communicated to all the senders and
receivers by some out-of-band mechanism. When an RSVP session is
being set up, the following events happen at the end systems.

H1 A receiver joins the multicast group specified by
DestAddress, using IGMP.

H2 A potential sender starts sending RSVP PATH Path messages to the
DestAddress.

H3 A receiver application receives a PATH Path message.

H4 A receiver starts sending appropriate RESV messages,

Braden, Zhang, et al. Expiration: August 1996 [Page 29] 30]

Internet Draft RSVP Specification February 1996

H4 A receiver starts sending appropriate Resv messages,
specifying the desired flow descriptors.

H5 A sender application receives a RESV Resv message.

H6 A sender starts sending data packets.

There are several synchronization considerations.

o H1 and H2 may happen in either order.

o Suppose that a new sender starts sending data (H6) but there
are no multicast routes because no receivers have joined the
group (H1). Then the data will be dropped at some router
node (which node depends upon the routing protocol) until
receivers(s) appear.

o Suppose that a new sender starts sending PATH Path messages (H2)
and data (H6) simultaneously, and there are receivers but no
RESV
Resv messages have reached the sender yet (e.g., because its
PATH
Path messages have not yet propagated to the receiver(s)).
Then the initial data may arrive at receivers without the
desired QoS. The sender could mitigate this problem by
awaiting arrival of the first RESV Resv message (H5); however,
receivers that are farther away may not have reservations in
place yet.

o If a receiver starts sending RESV Resv messages (H4) before
receiving any PATH Path messages (H3), RSVP will return error
messages to the receiver.

The receiver may simply choose to ignore such error messages,
or it may avoid them by waiting for PATH Path messages before
sending RESV Resv messages.

A specific application program interface (API) for RSVP is not
defined in this protocol spec, as it may be host system dependent.
However, Section 3.10.1 discusses the general requirements and
outlines a generic interface.

Braden, Zhang, et al. Expiration: August 1996 [Page 30] 31]

Internet Draft RSVP Specification February 1996

3. RSVP Functional Specification

3.1 RSVP Message Formats

An RSVP message or message fragment consists of a common header,
an optional integrity-check data structure, and a body consisting
of a variable number of variable-length, typed "objects". The
integrity-check data structure is itself an object, of class
INTEGRITY [Baker96]. In a fragmented message, INTEGRITY objects
must occur either in every fragment or else in no fragment.
Fragmentation of a message allows division of an object across two
(or more) successive fragments.

The following subsections define the formats of the common header,
the object structures, and each of the RSVP message types. For
each RSVP message type, there is a set of rules for the
permissible choice of object types. These rules are specified
using Backus-Naur Form (BNF) augmented with square brackets
surrounding optional sub-sequences. The BNF implies an order for
the objects in a message. However, in many (but not all) cases,
object order makes no logical difference. An implementation
should create messages with the objects in the order shown here,
but accept the objects in any order except where the order is
logically required (as noted in the following).

3.1.1 Common Header

The fields in the common header are as follows:

Vers: 4 bits

Protocol version number. This is version 1.

Flags: 4 bits

Braden, Zhang, et al. Expiration: August 1996 [Page 31] 32]

Internet Draft RSVP Specification February 1996

0x01 = INTEGRITY object present

This flag indicates that an INTEGRITY object follows
immediately after the common header. The use of the
INTEGRITY object is described in [Baker96].

0x02 = UDP': UDP encapsulation marker flag

This flag is reserved for use by UDP encapsulation
[Appendix C].

0x02-0x80: Reserved

Type: 8 bits

1 = PATH

2 = RESV

3 = PERR

4 = RERR

5 = PTEAR

6 = RTEAR

7 = RACK

RSVP Checksum: 16 bits

The one's complement of the one's complement sum of the
message (fragment), with the checksum field replaced by
zero for the purpose of computing the checksum. An all-
zero value means that no checksum was transmitted.

RSVP Length: 16 bits

The total length of this RSVP packet in bytes, including
the common header and the variable-length objects that
follow. If the MF flag is on or the Fragment Offset field
is non-zero, this is will generally differ from the length of
the current fragment of
a larger message. fragment.

Send_TTL: 8 bits

The IP TTL value with which the message was sent.

Message ID: 32 bits

An unique identifying value that is used to identify and
reassemble the fragments of a single message. It is
assigned to the RSVP message by the node whose address is

Braden, Zhang, et al. Expiration: August 1996 [Page 32] 33]

Internet Draft RSVP Specification February 1996

A label shared by all fragments of one message from a
given next/previous RSVP hop. An RSVP implementation
assigns a unique Message ID to each

the IP source address of the message it sends. (fragment).

MF: More Fragments Flag: 1 bit

This flag is the low-order bit of a byte; the seven high-
order bits are reserved. It is on for all but the last
fragment of a message.

Fragment Offset: 24 bits

This field gives the byte offset of the current fragment
in the complete message.

For a Path or PathTear message, the Message Id is assigned by
the sender host, and it must be copied at each successive node
into forwarded messages. For other messages, it is assigned at
the most recent RSVP hop to forward the message. When a
message is fragmented, the Messsage Id must be copied into each
fragment. When a fragmented packet is received, it may be
reassembled by RSVP out of fragments carrying the same Message
Id and IP source address.

RSVP messages that exceed the MTU of the interface on which
they are being sent must be split into fragments, each of which
will fit into an MTU.

3.1.2 Object Formats

Every object consists of one or more 32-bit words with a one-
word header, in the following format:

0 1 2 3
+-------------+-------------+-------------+-------------+
| Length (bytes) | Class-Num | C-Type |
+-------------+-------------+-------------+-------------+
| |
// (Object contents) //
| |
+-------------+-------------+-------------+-------------+

An object header has the following fields:

Length

A 16-bit field containing the total object length in
bytes. Must always be a multiple of 4, and at least 4.

Braden, Zhang, et al. Expiration: August 1996 [Page 34]

Internet Draft RSVP Specification February 1996

Class-Num

Identifies the object class; values of this field are
defined in Appendix A. Each object class has a name,
which is always capitalized in this document. An RSVP
implementation must recognize the following classes:

NULL

A NULL object has a Class-Num of zero, and its C-Type
is ignored. Its length must be at least 4, but can

Braden, Zhang, et al. Expiration: August 1996 [Page 33]

Internet Draft RSVP Specification February 1996
be any multiple of 4. A NULL object may appear
anywhere in a sequence of objects, and its contents
will be ignored by the receiver.

SESSION

Contains the IP destination address (DestAddress),
the IP protocol id, and a generalized destination
port, to define a specific session for the other
objects that follow. Required in every RSVP message.

RSVP_HOP

Carries the IP address of the RSVP-capable node that
sent this message. This document refers to a
RSVP_HOP object as a PHOP ("previous hop") object for
downstream messages or as a NHOP ("next hop") object
for upstream messages.

TIME_VALUES

Contains the value for the refresh period R used by
the creator of the message; see 3.6. Required in
every PATH Path and RESV Resv message.

STYLE

Defines the reservation style plus style-specific
information that is not in FLOWSPEC or FILTER_SPEC
objects. Required in every RESV Resv message.

FLOWSPEC

Defines a desired QoS, in a RESV Resv message.

FILTER_SPEC

Braden, Zhang, et al. Expiration: August 1996 [Page 35]

Internet Draft RSVP Specification February 1996

Defines a subset of session data packets that should
receive the desired QoS (specified by an FLOWSPEC
object), in a RESV Resv message.

SENDER_TEMPLATE

Contains a sender IP address and perhaps some
additional demultiplexing information to identify a
sender, in a PATH Path message.

SENDER_TSPEC

Braden, Zhang, et al. Expiration: August 1996 [Page 34]

Internet Draft RSVP Specification February 1996

Defines the traffic characteristics of a sender's
data stream, in a PATH Path message.

ADSPEC

Carries OPWA data, in a PATH Path message.

ERROR_SPEC

Specifies an error, in a PERR PathErr or RERR ResvErr message.

POLICY_DATA

Carries information that will allow a local policy
module to decide whether an associated reservation is
administratively permitted. May appear in a PATH Path,
Resv, PathErr, or
RESV ResvErr message.

INTEGRITY

Contains cryptographic data to authenticate the
originating node and to verify the contents of this
RSVP message. See [Baker96].

SCOPE

An explicit list of sender hosts towards which to
forward a message. May appear in a RESV, RERR, Resv, ResvErr, or
RTEAR
ResvTear message.

RESV_CONFIRM

Carries the IP address of a receiver that requested a
confirmation. May appear in a RESV Resv or RACK ResvConf
message.

Braden, Zhang, et al. Expiration: August 1996 [Page 36]

Internet Draft RSVP Specification February 1996

C-Type

Object type, unique within Class-Num. Values are defined
in Appendix A.

The maximum object content length is 65528 bytes. The Class-
Num and C-Type fields may be used together as a 16-bit number
to define a unique type for each object.

The high-order two bits of the Class-Num is used to determine
what action a node should take if it does not recognize the
Class-Num of an object; see Section 3.9.

Braden, Zhang, et al. Expiration: August 1996 [Page 35]

Internet Draft RSVP Specification February 1996

3.1.3 Path Messages

Each sender host periodically sends a PATH Path message containing a
description of each data stream it originates. The PATH Path
message travels from a sender to receiver(s) along the same
path(s) used by the data packets. The IP source address of a
PATH
Path message is an address of the sender it describes, while
the destination address is the DestAddress for the session.
These addresses assure that the message will be correctly
routed through a non-RSVP cloud.

Each RSVP-capable node along the path(s) captures PATH Path messages
and processes them to build local path state. The node then
forwards the PATH Path messages towards the receiver(s), replicating
it as dictated by multicast routing, while preserving the
original IP source address. PATH Path messages eventually reach the
applications on all receivers; however, they are not looped
back to a receiver running in the same application process as
the sender.

The format of a PATH Path message is as follows:

<Path Message> ::= <Common Header> [ <INTEGRITY> ]

<TIME_VALUES>

[ <POLICY_DATA> ... ]

[ <POLICY_DATA> ] [ <ADSPEC> ]

Braden, Zhang, et al. Expiration: August 1996 [Page 37]

Internet Draft RSVP Specification February 1996

If the INTEGRITY object is present, there must be an INTEGRITY
object immediately following the common header in every
fragment of the message, in this and all other messages. The
objects included in the sender descriptor must occur after all There
are no other objects in requirements on transmission order, although the message.
above order is recommended. Any number of POLICY_DATA objects
may appear.

The PHOP (i.e., the RSVP_HOP) object of each PATH Path message
contains the address of the interface through which the PATH Path
message was most recently sent. The SENDER_TEMPLATE object
defines the format of data packets from this sender, while the
SENDER_TSPEC object specifies the traffic characteristics of
the flow. Optionally, there may be a POLICY_DATA object
specifying user credential and accounting information and/or an

Braden, Zhang, et al. Expiration: August 1996 [Page 36]

Internet Draft RSVP Specification February 1996 ADSPEC object carrying
advertising (OPWA) data.

A PATH Path message received at a node is processed to create path
state for the sender defined by the SENDER_TEMPLATE and SESSION
objects. Any POLICY_DATA, SENDER_TSPEC, and ADSPEC objects are
also saved in the path state. If an error is encountered while
processing a PATH Path message, a PERR PathErr message is sent to the
originating sender of the PATH Path message. PATH messages must
satisfy the rules on SrcPort and DstPort in Section 2.2.

Periodically, the RSVP daemon at a node scans the path state to
create new PATH Path messages to forward downstream. Each message
contains a sender descriptor defining one sender. The RSVP
daemon forwards these messages using routing information it
obtains from the appropriate uni-/multicast routing daemon.
The route depends upon the session DestAddress, and for some
routing protocols also upon the source (sender's IP) address.
The routing information generally includes the list of none or
more outgoing interfaces to which the PATH Path message to be
forwarded. Because each outgoing interface has a different IP
address, the PATH Path messages sent out different interfaces
contain different PHOP addresses. In addition, any ADSPEC or
POLICY_DATA objects
carried in PATH Path messages will also generally differ for
different outgoing interfaces.

Some IP multicast routing protocols (e.g., DVMRP, PIM, and
MOSPF) also keep track of the expected incoming interface for
each source host to a multicast group. Whenever this
information is available, RSVP should check the incoming
interface of each PATH Path message and immediately discard those
messages that have arrived on the wrong interface.

Braden, Zhang, et al. Expiration: August 1996 [Page 38]

Internet Draft RSVP Specification February 1996

3.1.4 Resv Messages

RESV

Resv messages carry reservation requests hop-by-hop from
receivers to senders, along the reverse paths of data flows for
the session. The IP destination address of a RESV Resv message is
the unicast address of a previous-hop node, obtained from the
path state. The IP source address is an address of the node
that sent the message.

The RESV Resv message format is as follows:

<Resv Message> ::= <Common Header> [ <INTEGRITY> ]

<TIME_VALUES>

[ <S_POLICY_DATA> <POLICY_DATA> ... ]

Braden, Zhang, et al. Expiration: August 1996 [Page 37]

Internet Draft RSVP Specification February 1996

[ <RESV_CONFIRM> ] [ <SCOPE> ]

<S_POLICY_DATA> ::= <POLICY_DATA>

<flow descriptor list> ::= <flow descriptor> |

The NHOP (i.e., the RSVP_HOP) object contains the IP address of
the interface through which the RESV Resv message was sent. The
appearance of a RESV_CONFIRM object signals a request for a
reservation confirmation and carries the IP address of the
receiver to which the RACK ResvConf should be sent. The S_POLICY_DATA
object is a Any number of
POLICY_DATA object that is associated with the
entire session. There objects may also be flow-specific F_POLICY_DATA
objects, as described below. appear.

The STYLE object followed by the flow descriptor list must
occur at the end of the message. There are no other
requirements on transmission order, although the above order is
recommended.

The BNF above defines a flow descriptor list as simply a list
of flow descriptors. The following style-dependent rules
specify in more detail the composition of a valid flow
descriptor list for each of the reservation styles; the order
shown must be used.

o WF Style:

Braden, Zhang, et al. Expiration: August 1996 [Page 39]

Internet Draft RSVP Specification February 1996

<WF flow descriptor> ::= <FLOWSPEC> [ <F_POLICY_DATA> ]

<F_POLICY_DATA> ::= <POLICY_DATA>

o FF style:

<FLOWSPEC> <FILTER_SPEC> |

<First FF flow descriptor> ::=

Braden, Zhang, et al. Expiration: August 1996 [Page 38]

Internet Draft RSVP Specification February 1996

<FF flow descriptor> ::=

[ <FLOWSPEC> ] [ <F_POLICY_DATA> ] <FILTER_SPEC>

Each elementary FF style request is defined by a single
(FLOWSPEC, FILTER_SPEC) pair, and multiple such requests
may be packed into the flow descriptor list of a single
RESV
Resv message. A FLOWSPEC object can be omitted if it is
identical to the most recent such object that appeared in
the list; the first FF flow descriptor must contain a
FLOWSPEC.

Each flow descriptor in the list must be processed
independently, and a separate RERR ResvErr message must be
generated for each one that is in error.

o SE style:

<SE flow descriptor> ::=

| <filter spec list> <FILTER_SPEC>

The reservation scope, i.e., the set of senders towards which a
particular reservation is to be forwarded, is determined as
follows:

Braden, Zhang, et al. Expiration: August 1996 [Page 40]

Internet Draft RSVP Specification February 1996

o Explicit sender selection

Select a particular sender by matching each FILTER_SPEC
object against the path state created from SENDER_TEMPLATE
objects. An ambiguous match, i.e., a FILTER_SPEC matching
more than one SENDER_TEMPLATE (e.g. through use of a
wildcard port), is an error.

o Wildcard sender selection

All senders that route to the given outgoing interface
match this request. A SCOPE object, if present, contains
an explicit list of sender IP addresses. If there is no

Braden, Zhang, et al. Expiration: August 1996 [Page 39]

Internet Draft RSVP Specification February 1996
SCOPE object, the scope is determined by the relevant set
of senders in the path state.

Whenever a RESV Resv message with wildcard sender selection is
forwarded to more than one previous hop, a SCOPE object
must be included in the message. See Section 3.3 below.

3.1.5 Teardown Messages

There are two types of RSVP Teardown message, PTEAR PathTear and RTEAR.
ResvTear.

o A PTEAR PathTear message deletes path state (which in turn
deletes any reservation state for that sender) and travels
towards all receivers that are downstream from the
initiating node. A PTEAR PathTear message is routed like a PATH Path
message, and its IP destination address is DestAddress for
the session.

o A RTEAR ResvTear message deletes reservation state and travels
towards all matching senders upstream from the initiating
node. A RTEAR ResvTear message is routed in the same way as a
corresponding RESV Resv message, and its IP destination address
is the unicast address of a previous hop.

<PathTear Message> ::= <Common Header> [<INTEGRITY>]

<sender descriptor> ::= (see earlier definition)

<ResvTear Message> ::= <Common Header> [<INTEGRITY>]

Braden, Zhang, et al. Expiration: August 1996 [Page 41]

Internet Draft RSVP Specification February 1996

[ <SCOPE> ] <STYLE>

<flow descriptor list> ::= (see earlier definition)

FLOWSPEC or POLICY_DATA objects in the flow descriptor list of a RTEAR ResvTear
message will be ignored and may be omitted. The order
requirements for sender descriptor, STYLE object, and flow
descriptor list are as given earlier for PATH Path and RESV Resv
messages.

Braden, Zhang, et al. Expiration: August 1996 [Page 40]

Internet Draft RSVP Specification February 1996

Note that, unless it is accidentally dropped along the way, a
PTEAR message will reach all receivers down stream from its
origination. On the other hand, a RTEAR ResvTear message will cease
to be forwarded at the same node where merging suppresses
forwarding of the corresponding RESV Resv messages. In each node N
along the way, if the RTEAR ResvTear message causes the removal of
all state for this session, N will create a new teardown
message to be propagated further upstream; otherwise, the RTEAR
ResvTear message may result in the immediate forwarding of a
modified RESV Resv refresh message.

Deletion of path state as the result of a PTEAR PathTear message or a
timeout must cause any adjustments in related reservation state
required to maintain consistency in the local node. The
adjustment in reservation state depends upon the style. For
example, suppose a PTEAR PathTear deletes the path state for a sender
S. If the style specifies explicit sender selection (FF or
SE), any reservation with a filter spec matching S should be
deleted; if the style has wildcard sender selection (WF), the
reservation should be deleted if S is the last sender to the
session. These reservation changes should not trigger an
immediate RESV Resv refresh message, since the PTEAR PathTear message have
already made the required changes upstream. However, at the
node in which a RTEAR ResvTear message stops, the change of
reservation state may trigger a RESV Resv refresh starting at that
node.

3.1.6 Error Messages

There are two types of RSVP error messages.

o PERR PathErr messages result from PATH Path messages and travel
upstream towards the senders. PERR PathErr messages are routed

Braden, Zhang, et al. Expiration: August 1996 [Page 42]

Internet Draft RSVP Specification February 1996

hop-by-hop using the path state; at each hop, the IP
destination address is the unicast address of a previous
hop. PERR PathErr messages do not modify the state of any node
through which they pass; instead, they are only reported
to the sender application.

o RERR ResvErr messages result from RESV Resv messages and travel
downstream towards the appropriate receivers. They are
routed hop-by-hop using the reservation state; at each
hop, the IP destination address is the unicast address of
a next-hop node.

An error encountered while processing an error message must
cause the error message to be discarded without creating
further error messages; however, logging of such events may be
useful.

Braden, Zhang, et al. Expiration: August 1996 [Page 41]

Internet Draft RSVP Specification February 1996

<PathErr message> ::= <Common Header> [ <INTEGRITY> ]

[ <POLICY_DATA> ...]

<sender descriptor> ::= (see earlier definition)

<ResvErr Message> ::= <Common Header> [ <INTEGRITY> ]

[S_POLICY_DATA]

[ <POLICY_DATA> ...]

[ <SCOPE> ]

The ERROR_SPEC object specifies the error and includes the IP
address of the node that detected the error (Error Node
Address). One or more POLICY_DATA objects are may be included in
an error messages
in cases where they may message to provide relevant information (i.e., when an
administrative failure is being reported). The STYLE object is
copied from the RESV Resv message in error. The use of the SCOPE
object in a RERR ResvErr message is defined below in Section 3.3.

Braden, Zhang, et al. Expiration: August 1996 [Page 43]

Internet Draft RSVP Specification February 1996

The following style-dependent rules define the composition of a
valid error flow descriptor; the object order requirements are
as given earlier for a RESV Resv message.

o WF Style:

o FF style:

o SE style:

Note that a RERR ResvErr message contains only one flow descriptor.
Therefore, a RESV Resv message that contains N > 1 flow descriptors

Braden, Zhang, et al. Expiration: August 1996 [Page 42]

Internet Draft RSVP Specification February 1996
(FF style) may create up to N separate RERR ResvErr messages.

Generally speaking, a RERR ResvErr message should be forwarded
towards all receivers that may have caused the error being
reported. More specifically:

o The node that detects an error in a reservation request
sends a RERR message to the next hop from which the
erroneous reservation came.

This message must contain the information required to
define the error and to route the error message in later
hops. It therefore includes an ERROR_SPEC object, a copy
of the STYLE object, and the appropriate error flow
descriptor. If the error is an admission control failure,
any reservation already in place will be left in place,
and the InPlace flag bit must be on in the ERROR_SPEC of
the RERR ResvErr message.

o Succeeding nodes forward the RERR ResvErr message to next hops
that have local reservation state. For reservations with
wildcard scope, there is an additional limitation on
forwarding RERR ResvErr messages, to avoid loops; see Section
3.3. There is also a rule restricting the forwarding of RESV
Resv messages for Admission Control failures; see Section
3.4.

Braden, Zhang, et al. Expiration: August 1996 [Page 44]

Internet Draft RSVP Specification February 1996

A RERR ResvErr message that is forwarded should carry the
FILTER_SPEC from the corresponding reservation state.

o When a RERR ResvErr message reaches a receiver, the STYLE
object, flow descriptor list, and ERROR_SPEC object
(including its flags) should be delivered to the receiver
application.

3.1.7 Confirmation Messages

RACK

ResvConf messages are sent to (probabilistically) acknowledge
reservation requests. A RACK ResvConf message is sent as the result
of the appearance of a RESV_CONFIRM object in a RESV Resv message.

A RACK ResvConf message is sent to the unicast address of a receiver
host; the address is obtained from the RESV_CONFIRM object.
However, a RACK ResvConf message is forwarded to the receiver hop-by-
hop, hop-
by-hop, to accommodate the hop-by-hop integrity check
mechanism.

<ERROR_SPEC>

Braden, Zhang, et al. Expiration: August 1996 [Page 43]

Internet Draft RSVP Specification February 1996

<RESV_CONFIRM>

<flow descriptor list> ::= (see earlier definition)

The RESV_CONFIRM object is a copy of that object in the RESV Resv
message that triggered the confirmation. The ERROR_SPEC is
used only to carry the IP address of the originating node, in
the Error Node Address; the Error Code and Value are zero to
indicate a confirmation. The flow descriptor list specifies
the particular reservations that are being confirmed; it may be
a subset of flow descriptor list of the Resv that requested the
confirmation.

The object order requirements within the flow descriptor list
are the same as those given earlier for a RESV Resv message.

3.2 Sending RSVP Messages

RSVP messages are sent hop-by-hop between RSVP-capable routers as
"raw" IP packets with protocol number 46. Raw IP packets are

Braden, Zhang, et al. Expiration: August 1996 [Page 45]

Internet Draft RSVP Specification February 1996

intended to be used between an end system and the first/last hop
router, although it is also possible to encapsulate RSVP messages
as UDP datagrams for end-system communication, as described in
Appendix C. UDP encapsulation is needed for systems that cannot
do raw network I/O.

PATH, PTEAR,

Path, PathTear, and RACK ResvConf messages must be sent with the Router
Alert IP option [Katz95] in their IP headers. This option may be
used in the fast forwarding path of a high-speed router to detect
datagrams that require special processing.

Upon the arrival of an RSVP message M that changes the state, a
node must forward the modified state immediately. However, this
must not trigger sending an message out the interface through
which M arrived (as could happen if the implementation simply
triggered an immediate refresh of all state for the session).
This rule is necessary to prevent packet storms on broadcast LANs.

An RSVP message must be fragmented when necessary to fit into the
MTU of the interface through which it will be sent. All fragments
of the message should carry the same unique value of the Message
ID field, as well as appropriate Fragment Offset and MF bits, in
their common headers. When an RSVP message arrives, it must be
reassembled before it can be processed. The refresh period R can
be used as an appropriate reassembly timeout time.

Between adjacent RSVP-capable routers, RSVP-level fragmentation
mechanism should normally be used in lieu of fragmentation at the
IP level. However, IP-level fragmentation may still occur when

Braden, Zhang, et al. Expiration: August 1996 [Page 44]

Internet Draft RSVP Specification February 1996
RSVP messages travel through a non-RSVP cloud. In case of IP6,
which does not support IP fragmentation at routers, an RSVP
implementation must use Path MTU Discovery or hand configuration
to obtain an appropriate MTU between adjacent RSVP neighbors.

RSVP uses its periodic refresh mechanisms to recover from
occasional packet losses. Under network overload, however,
substantial losses of RSVP messages could cause a failure of
resource reservations. To control the queueing delay and dropping
of RSVP packets, routers should be configured to offer them a
preferred class of service. If RSVP packets experience noticeable
losses when crossing a congested non-RSVP cloud, a larger value
can be used for the timeout factor K (see section 3.6 below).

Some multicast routing protocols provide for "multicast tunnels",
which encapsulate multicast packets for transmission through
routers that do not have multicast capability. A multicast tunnel
looks like a logical outgoing interface that is mapped into some
physical interface. A multicast routing protocol that supports

Braden, Zhang, et al. Expiration: August 1996 [Page 46]

Internet Draft RSVP Specification February 1996

tunnels will describe a route using a list of logical rather than
physical interfaces. RSVP can run through multicast tunnels in
the following manner:

1. When a node N forwards a PATH Path message out a logical outgoing
interface L, it includes in the message some encoding of the
identity of L, called the "logical interface handle" or LIH.
The LIH value is carried in the RSVP_HOP object.

2. The next hop node N' stores the LIH value in its path state.

3. When N' sends a RESV Resv message to N, it includes the LIH value
from the path state (again, in the RSVP_HOP object).

4. When the RESV Resv message arrives at N, its LIH value provides
the information necessary to attach the reservation to the
appropriate logical interface. Note that N creates and
interprets the LIH; it is an opaque value to N'.

3.3 Avoiding RSVP Message Loops

Forwarding of RSVP messages must avoid looping. In steady state,
PATH
Path and RESV Resv messages are forwarded only once per refresh period
on each hop. This avoids looping packets, but there is still the
possibility of an "auto-refresh" loop, clocked by the refresh
period. Such auto-refresh loops keep state active "forever", even
if the end nodes have ceased refreshing it, until either the
receivers leave the multicast group and/or the senders stop
sending PATH Path messages. On the other hand, error and teardown

Braden, Zhang, et al. Expiration: August 1996 [Page 45]

Internet Draft RSVP Specification February 1996
messages are forwarded immediately and are therefore subject to
looping.

Consider each message type.

o PATH Path Messages

PATH

Path messages are forwarded in exactly the same way as IP
data packets. Therefore there should be no loops of PATH Path
messages, even in a topology with cycles.

o PTEAR PathTear Messages

PTEAR

PathTear messages use the same routing as PATH Path messages and
therefore cannot loop.

o PERR PathErr Messages

Since PATH Path messages do not loop, they create path state

Braden, Zhang, et al. Expiration: August 1996 [Page 47]

Internet Draft RSVP Specification February 1996

defining a loop-free reverse path to each sender. PERR PathErr
messages are always directed to particular senders and
therefore cannot loop.

o RESV Resv Messages

RESV

Resv messages directed to particular senders (i.e., with
explicit sender selection) cannot loop. However, RESV Resv
messages with wildcard sender selection (WF style) have a
potential for auto-refresh looping.

o RTEAR ResvTear Messages

Although RTEAR ResvTear messages are routed the same as RESV Resv
messages, during the second pass around a loop there will be
no state so any RTEAR ResvTear message will be dropped. Hence
there is no looping problem here.

o RERR ResvErr Messages

RERR

ResvErr messages for WF style reservations may loop for
essentially the same reasons that RESV Resv messages loop.

o RACK ResvConf Messages

RACK

ResvConf messages are forwarded towards a fixed unicast
receiver address and cannot loop.

If the topology has no loops, then looping of RESV Resv and RERR

Braden, Zhang, et al. Expiration: August 1996 [Page 46]

Internet Draft RSVP Specification February 1996 ResvErr
messages with wildcard sender selection can be avoided by simply
enforcing the rule given earlier: state that is received through a
particular interface must never be forwarded out the same
interface. However, when the topology does have cycles, further
effort is needed to prevent auto-refresh loops of wildcard RESV Resv
messages and fast loops of wildcard RERR ResvErr messages. The
solution to this problem adopted by this protocol specification is
for such messages to carry an explicit sender address list in a
SCOPE object.

When a RESV Resv message with WF style is to be forwarded to a
particular previous hop, a new SCOPE object is computed from the
SCOPE objects that were received in matching RESV Resv messages. If
the computed SCOPE object is empty, the message is not forwarded
to the previous hop; otherwise, the message is sent containing the
new SCOPE object. The rules for computing a new SCOPE object for
a RESV Resv message are as follows:

1. The union is formed of the sets of sender IP addresses listed

Braden, Zhang, et al. Expiration: August 1996 [Page 48]

Internet Draft RSVP Specification February 1996

in all SCOPE objects in the reservation state for the given
session.

If reservation state from some NHOP does not contain a SCOPE
object, a substitute sender list must be created and included
in the union. For a message that arrived on outgoing
interface OI, the substitute list is the set of senders that
route to OI.

2. Any local senders (i.e., any sender applications on this
node) are removed from this set.

3. If the SCOPE object is to be sent to PHOP, remove from the
set any senders that did not come from PHOP.

Figure 11 shows an example of wildcard-scoped (WF style) RESV Resv
messages. The address lists within SCOPE objects are shown in
square brackets. Note that there may be additional connections
among the nodes, creating looping topology that is not shown.

Braden, Zhang, et al. Expiration: August 1996 [Page 47]

Internet Draft RSVP Specification February 1996

________________
a | | c
R4, S4<----->| Router |<-----> R2, S2, S3
| |
b | |
R1, S1<----->| |
|________________|

Figure 11: SCOPE Objects in Wildcard-Scope Reservations

Braden, Zhang, et al. Expiration: August 1996 [Page 49]

Internet Draft RSVP Specification February 1996

SCOPE objects are not necessary if the multicast routing uses
shared trees or if the reservation style has explicit sender
selection. Furthermore, attaching a SCOPE object to a reservation
may be deferred to a node which has more than one previous hop
upstream.

The following rules are used for SCOPE objects in RERR ResvErr messages
with WF style:

1. The node that detected the error initiates an RERR ResvErr message
containing a copy of the SCOPE object associated with the
reservation state or message in error.

2. Suppose a wildcard-scoped RERR ResvErr message arrives at a node
with a SCOPE object containing the sender host address list
L. The node forwards the RERR ResvErr message using the rules of
Section 3.1.6. However, the RERR ResvErr message forwarded out OI
must contain a SCOPE object derived from L by including only
those senders that route to OI. If this SCOPE object is
empty, the

Braden, Zhang, et al. Expiration: August 1996 [Page 48]

Internet Draft RSVP Specification February 1996

RERR ResvErr message should not be sent out OI.

3.4 Blockade State

The basic rule for creating a RESV Resv refresh message is to merge the
flowspecs of the reservation requests in place in the node, by
computing their LUB. However, this rule is modified by the
existence of "blockade state" resulting from RERR ResvErr messages, to
solve the KR-II problem (Section 2.6). The blockade state also
enters into the routing of RERR ResvErr messages for Admission Control
failure.

When a RERR ResvErr message for an Admission Control failure is
received, its flowspec Qe is used to create or refresh an element
of local blockade state. Each element of blockade state consists
of a blockade flowspec Qb taken from the flowspec of the last RERR,
ResvErr, and an associated blockade timer Tb. When the blockade
timer expires, the blockade state is deleted.

The granularity of blockade state depends upon the style of the
RERR
ResvErr message that created it. For an explicit style, there may
be a blockade state element (Qb(S),Tb(S)) for each sender S. For
a wildcard style, blockade state is per previous hop P.

An element of blockade state with flowspec Qb is said to
"blockade" a reservation with flowspec Qi if Qb is not (strictly)
greater than Qi. For example, suppose that the LUB of two
flowspecs is computed by taking the max of each of their
corresponding components. Then Qb blockades Qi if for some

Braden, Zhang, et al. Expiration: August 1996 [Page 50]

Internet Draft RSVP Specification February 1996

component j, Qb[j] <= Qi[j].

Suppose that a node receives a RERR ResvErr message from previous hop P
(or, if style is explicit, sender S) as the result of an Admission
Control failure upstream. Then:

1. An element of blockade state is created for P (or S) if it
did not exist.

2. Qb(P) (or Qb(S)) is set equal to the flowspec Qe from the
RERR
ResvErr message.

3. A corresponding blockade timer Tb(P) (or Tb(S)) is started or
restarted for a time Kb*R. Here Kb is a fixed multiplier and
R is the refresh interval for reservation state. Kb should
be configurable.

4. If there is some local reservation state that is not
blockaded (see below), an immediate reservation refresh for P

Braden, Zhang, et al. Expiration: August 1996 [Page 49]

Internet Draft RSVP Specification February 1996
(or S) is generated.

5. The RERR ResvErr message is forwarded to next hops in the
following way. If the InPlace bit is off, the RERR ResvErr
message is forwarded to all next hops for which there is
reservation state. If the InPlace bit is on, the RERR ResvErr
message is forwarded only to the next hops whose Qi is
blockaded by Qb.

Finally, we present the modified rule for merging flowspecs to
create a reservation refresh message.

o If there are any local reservation requests Qi that are not
blockaded, these are merged by computing their LUB. The
blockaded reservations are ignored; this allows forwarding of
a smaller reservation that has not failed and may perhaps
succeed, after a larger reservation fails.

o Otherwise (all local requests Qi are blockaded), they are
merged by taking the GLB (Greatest Lower Bound) of the Qi's.

This refresh merging algorithm is applied separately to each flow
(each sender or PHOP) contributing to a shared reservation (WF or
SE style).

Figure 12 shows an example of the the application of blockade
state for a shared reservation (WF style). There are two previous
hops labelled (a) and (b), and two next hops labelled (c) and (d).
The larger reservation 4B arrived from (c) first, but it failed

Braden, Zhang, et al. Expiration: August 1996 [Page 51]

Internet Draft RSVP Specification February 1996

somewhere upstream via PHOP (a), but not via PHOP (b). The
figures show the final "steady state" after the smaller
reservation 2B subsequently arrived from (d). This steady state
is perturbed roughly every Kb*R seconds, when the blockade state
times out. The next refresh then sends 4B to previous hop (a);
presumably this will fail, sending a RERR ResvErr message that will re-
establish
re-establish the blockade state, returning to the situation shown
in the figure. At the same time, the RERR ResvErr message will be
forwarded
to next hop (c) and to all receivers downstream responsible for
the 4B reservations.

Braden, Zhang, et al. Expiration: August 1996 [Page 50]

Internet Draft RSVP Specification February 1996 to next hop (c) and to all receivers downstream
responsible for the 4B reservations.

Send Blockade| Reserve Receive
State|
|
| ________
(a) <- WF(*{2B}) {4B} | | * {4B} | WF(*{4B}) <- (c)
| |________|
|
---------------------------|-------------------------------
|
| ________
(b) <- WF(*{4B}) (none)| | * {2B} | WF(*{2B}) <- (d)
| |________|

Figure 12: Blockading with Shared Style

3.5 Local Repair

When a route changes, the next PATH Path or RESV Resv refresh message will
establish path or reservation state (respectively) along the new
route. To provide fast adaptation to routing changes without the
overhead of short refresh periods, the local routing protocol
module can notify the RSVP daemon of route changes for particular
destinations. The RSVP daemon should use this information to
trigger a quick refresh of state for these destinations, using the
new route.

The specific rules are as follows:

o When routing detects a change of the set of outgoing
interfaces for destination G, RSVP should wait for a short
period W, and then send PATH Path refreshes for all sessions G/*
(i.e., for any session with destination G, regardless of
destination port).

Braden, Zhang, et al. Expiration: August 1996 [Page 52]

Internet Draft RSVP Specification February 1996

The short wait period before sending PATH Path refreshes is to
allow the routing protocol getting settled with the new
change(s), and the exact value for W should be chosen
accordingly. Currently W = 2 sec is suggested; however, this
value should be configurable per interface.

o When a PATH Path message arrives with a Previous Hop address that
differs from the one stored in the path state, RSVP should
send immediate RESV Resv refreshes for that session.

Braden, Zhang, et al. Expiration: August 1996 [Page 51]

Internet Draft RSVP Specification February 1996

3.6 Time Parameters

There are two time parameters relevant to each element of RSVP
path or reservation state in a node: the refresh period R between
generation of successive refreshes for the state by the neighbor
node, and the local state's lifetime L. Each RSVP RESV Resv or PATH Path
message may contain a TIME_VALUES object specifying the R value
that was used to generate this (refresh) message. This R value is
then used to determine the value for L when the state is received
and stored. The values for R and L may vary from hop to hop.

In more detail:

1. Floyd and Jacobson [FJ94] have shown that periodic messages
generated by independent network nodes can become
synchronized. This can lead to disruption in network
services as the periodic messages contend with other network
traffic for link and forwarding resources. Since RSVP sends
periodic refresh messages, it must avoid message
synchronization and ensure that any synchronization that may
occur is not stable.

For this reason, the refresh timer should be randomly set to
a value in the range [0.5R, 1.5R].

2. To avoid premature loss of state, L must satisfy L >= (K +
0.5)*1.5*R, where K is a small integer. Then in the worst
case, K-1 successive messages may be lost without state being
deleted. To compute a lifetime L for a collection of state
with different R values R0, R1, ..., replace R by max(Ri).

Currently K = 3 is suggested as the default. However, it may
be necessary to set a larger K value for hops with high loss
rate. K may be set either by manual configuration per
interface, or by some adaptive technique that has not yet
been specified.

3. Each message that creates state (PATH Path or RESV message) Resv message carries a TIME_VALUES object

Braden, Zhang, et al. Expiration: August 1996 [Page 53]

Internet Draft RSVP Specification February 1996

containing the refresh time R used to generate refreshes; the refreshes.
The recipient node uses this R to determine the lifetime L of
the stored state. state created or refreshed by the message.

4. The refresh time R is chosen locally by each node. If the
node does not implement local repair of reservations
disrupted by route changes, a smaller R speeds up adaptation
to routing changes, while increasing the RSVP overhead. With
local repair, a router can be more relaxed about R since the
periodic refresh becomes only a backstop robustness
mechanism. A node may

Braden, Zhang, et al. Expiration: August 1996 [Page 52]

Internet Draft RSVP Specification February 1996 therefore adjust the effective R
dynamically to control the amount of overhead due to refresh
messages.

The current suggested default for R is 30 seconds. However,
the default should be configurable per interface.

5. When R is changed dynamically, there is a limit on how fast
it may increase. Specifically, the ratio of two successive
values R2/R1 must not exceed 1 + Slew.Max.

Currently, Slew.Max is 0.30. With K = 3, one packet may be
lost without state timeout while R is increasing 30 percent
per refresh cycle.

6. To improve robustness, a node may temporarily send refreshes
more often than R after a state change (including initial
state establishment).

7. The values of Rdef, K, and Slew.Max used in an implementation
should be easily modifiable per interface, as experience may
lead to different values. The possibility of dynamically
adapting K and/or Slew.Max in response to measured loss rates
is for future study.

The granularity of state for refresh and timeout is as follows:

o For reservation state, each FLOWSPEC is independently
refreshed and timed out.

o For path state, each sender is independently refreshed and
timed out.

3.7 Traffic Policing and Non-Integrated Service Hops

Some QoS services may require traffic policing at some or all of
(1) the edge of the network, (2) a merging point for data from
multiple senders, and/or (3) a branch point where traffic flow

Braden, Zhang, et al. Expiration: August 1996 [Page 54]

Internet Draft RSVP Specification February 1996

from upstream may be greater than the downstream reservation being
requested. RSVP knows where such points occur and must so
indicate to the traffic control mechanism. On the other hand,
RSVP does not interpret the service embodied in the flowspec and
therefore does not know whether policing will actually be applied
in any particular case.

The RSVP daemon passes to traffic control a separate policing flag
for each of these three situations.

o E_Police_Flag -- Entry Policing

This flag is set in the first-hop RSVP node that implements
traffic control (and is therefore capable of policing).

For example, sender hosts must implement RSVP but currently
many of them do not implement traffic control. In this case,
the E_Police_Flag should be off in the sender host, and it
should only be set on when the first node capable of traffic

Braden, Zhang, et al. Expiration: August 1996 [Page 53]

Internet Draft RSVP Specification February 1996
control is reached. This is controlled by the E_Police flag
in SESSION objects.

o M_Police_Flag -- Merge Policing

This flag should be set on for a reservation using a shared
style (WF or SE) when flows from more than one sender are
being merged.

o B_Police_Flag -- Branch Policing

This flag should be set on when the flowspec being installed
is smaller than, or incomparable to, a FLOWSPEC in place on
any other interface, for the same FILTER_SPEC and SESSION.

RSVP must also detect and report to receivers the presence of
non-RSVP (which implies non-integrated-service compliant) hops in
the path. For this purpose, an RSVP daemon sets the Non_RSVP flag
bit in SESSION object of PATH Path messages. With normal IP
forwarding, RSVP can detect a non-RSVP hop by comparing the IP TTL
with which a PATH Path message is sent to the TTL with which it is
received, and set the Non_RSVP bit on. For this purpose, the
transmission TTL is placed in the common header.

However, the TTL is not always a reliable indicator of non-RSVP
hops, and other means must be used. For example, if the routing
protocol uses IP encapsulating tunnels, then the routing protocol
must inform RSVP when non-RSVP hops are included. If no automatic
mechanism will work, manual configuration will be required.

Braden, Zhang, et al. Expiration: August 1996 [Page 55]

Internet Draft RSVP Specification February 1996

Finally, there may still be cases where an RSVP cannot reliably
determine whether or not a non-RSVP hop was used. To report this
to the receiver, the SESSION object carries another flag bit,
Maybe_RSVP.

3.8 Multihomed Hosts

Accommodating multihomed hosts requires some special rules in
RSVP. We use the term `multihomed host' to cover both hosts (end
systems) with more than one network interface [could ref. section
3.3.4 of RFC-1122], and routers that are
supporting local application programs.

An application executing on a multihomed host may explicitly
specify which interface any given flow will use for sending and/or
for receiving data packets, to override the system-specified
default interface. The RSVP daemon must be aware of the default,
and if an application sets a specific interface, it must also pass
that information to RSVP.

Braden, Zhang, et al. Expiration: August 1996 [Page 54]

Internet Draft RSVP Specification February 1996

o Sending Data

A sender application uses an API call (SENDER in Section
3.10.1) to declare to RSVP the characteristics of the data
flow it will originate. This call may optionally include the
local IP address of the sender. If it is set by the
application, this parameter must be the interface address for
sending the data packets; otherwise, the system default
interface is implied.

The RSVP daemon on the host then sends PATH Path messages for this
application out the specified interface (only).

o Making Reservations

A receiver application uses an API call (RESERVE in Section
3.10.1) to request a reservation from RSVP. This call may
optionally include the local IP address of the receiver,
i.e., the interface address for receiving data packets. In
the case of multicast sessions, this is the interface on
which the group has been joined. If the parameter is
omitted, the system default interface is used.

In general, the RSVP daemon should send RESV Resv messages for an
application out the specified interface. However, when the
application is executing on a router and the session is
multicast, a more complex situation arises. Suppose in this
case that a receiver application joins the group on an
interface Iapp that differs from Isp, the shortest-path

Braden, Zhang, et al. Expiration: August 1996 [Page 56]

Internet Draft RSVP Specification February 1996

interface to the sender. Then there are two possible ways
for multicast routing to deliver data packets to the
application. The RSVP daemon must determine which case holds
by examining the path state, to decide which incoming
interface to use for sending RESV Resv messages.

1. The multicast routing protocol may create a separate
branch of the multicast distribution `tree' to deliver
to Iapp. In this case, there will be path state for
both Isp and Iapp. The path state on Iapp should only
match a reservation from the local application; it must
be marked "Local_only" by the RSVP daemon. If
"Local_only" path state for Iapp exists, the RESV Resv
message should be sent out Iapp.

Note that it is possible for the path state blocks for
Isp and Iapp to have the same next hop, if there is an
intervening non-RSVP cloud.

Braden, Zhang, et al. Expiration: August 1996 [Page 55]

Internet Draft RSVP Specification February 1996 cloud.

2. The multicast routing protocol may forward data within
the router from Isp to Iapp. In this case, Iapp will
appear in the list of outgoing interfaces of the path
state for Isp, and the RESV Resv message should be sent out
Isp.

3.9 Future Compatibility

We may expect that in the future new object C-Types will be
defined for existing object classes, and perhaps new object
classes will be defined. It will be desirable to employ such new
objects within the Internet using older implementations that do
not recognize them. Unfortunately, this is only possible to a
limited degree with reasonable complexity. The rules are as
follows (`b' represents a bit).

1. Unknown Class

There are three possible ways that an RSVP implementation can
treat an object with unknown class. This choice is
determined by the two high-order bits of the Class-Num octet,
as follows.

o Class-Num = 0bbbbbbb

The entire message should be rejected and an "Unknown
Object Class" error returned.

o Class-Num = 10bbbbbb

Braden, Zhang, et al. Expiration: August 1996 [Page 57]

Internet Draft RSVP Specification February 1996

The node should ignore the object, neither forwarding it
nor sending an error message.

o Class-Num = 11bbbbbb

The node should ignore the object but forward it,
unexamined and unmodified, in all messages resulting
from the state contained in this message.

For example, suppose that a RESV Resv message that is received
contains an object of unknown class number 11bbbbbb. Such an
object should be saved in the reservation state without
further examination; however, only the latest object with a
given (unknown class, C-Type) pair should be saved. When a
RESV
Resv message is forwarded, it should include copies of such
saved unknown-class objects from all reservations that are
merged to form the new RESV Resv message.

Braden, Zhang, et al. Expiration: August 1996 [Page 56]

Internet Draft RSVP Specification February 1996

Note that objects with unknown class cannot be merged;
however, unmerged objects may be forwarded until they reach a
node that knows how to merge them. Forwarding objects with
unknown class enables incremental deployment of new objects;
however, the scaling limitations of doing so must be
carefully examined before a new object class is deployed with
both high bits on.

These rules should be considered when any new Class-Num is
defined.

2. Unknown C-Type for Known Class

One might expect the known Class-Num to provide information
that could allow intelligent handling of such an object.
However, in practice such class-dependent handling is
complex, and in many cases it is not useful.

Generally, the appearance of an object with unknown C-Type
should result in rejection of the entire message and
generation of an error message (RERR (ResvErr or PERR PathErr as
appropriate). The error message will include the Class-Num
and C-Type that failed (see Appendix B); the end system that
originated the failed message may be able to use this
information to retry the request using a different C-Type
object, repeating this process until it runs out of
alternatives or succeeds.

Objects of certain classes (FLOWSPEC, ADSPEC, and
POLICY_DATA) are opaque to RSVP, which simply hands them to

Braden, Zhang, et al. Expiration: August 1996 [Page 58]

Internet Draft RSVP Specification February 1996

traffic control or policy modules. Depending upon its
internal rules, either of the latter modules may reject a C-
Type and inform the RSVP daemon; RSVP should then reject the
message and send an error, as described in the previous
paragraph.

Braden, Zhang, et al. Expiration: August 1996 [Page 57] 59]

Internet Draft RSVP Specification February 1996

3.10 RSVP Interfaces

RSVP on a router has interfaces to routing and to traffic control.
RSVP on a host has an interface to applications (i.e, an API) and
also an interface to traffic control (if it exists on the host).

3.10.1 Application/RSVP Interface

This section describes a generic interface between an
application and an RSVP control process. The details of a real
interface may be operating-system dependent; the following can
only suggest the basic functions to be performed. Some of
these calls cause information to be returned asynchronously.

o Register Session

Call: SESSION( DestAddress , ProtocolId, DstPort ,

[ , SESSION_object ]

[ , Upcall_Proc_addr ] ) -> Session-id

This call initiates RSVP processing for a session, defined
by DestAddress together with ProtocolId and possibly a
port number DstPort. If successful, the SESSION call
returns immediately with a local session identifier
Session-id, which may be used in subsequent calls.

The Upcall_Proc_addr parameter defines the address of an
upcall procedure to receive asynchronous error or event
notification; see below. The SESSION_object parameter is
included as an escape mechanism to support some more
general definition of the session ("generalized
destination port"), should that be necessary in the
future. Normally SESSION_object will be omitted.

o Define Sender

Call: SENDER( Session-id,

[ , Source_Address ] [ , Source_Port ]

[ , Sender_Template ]

[ , Sender_Tspec ] [ , Data_TTL ]

[ , Sender_Policy_Data ] )

Braden, Zhang, et al. Expiration: August 1996 [Page 58] 60]

Internet Draft RSVP Specification February 1996

A sender uses this call to define, or to modify the
definition of, the attributes of the data stream. The
first SENDER call for the session registered as `Session-
id' will cause RSVP to begin sending PATH Path messages for
this session; later calls will modify the path
information.

The SENDER parameters are interpreted as follows:

- Source_Address

This is the address of the interface from which the
data will be sent. If it is omitted, a default
interface will be used. This parameter is needed on
a multihomed sender host.

- Source_Port

This is the UDP/TCP port from which the data will be
sent. If it is omitted or zero, the port is "wild"
and can match any port in a FILTER_SPEC.

- Sender_Template

This parameter is included as an escape mechanism to
support a more general definition of the sender
("generalized source port"). Normally this parameter
may be omitted.

- Sender_Tspec

This optional parameter describes the traffic flow to
be sent. It may be included to prevent over-
reservation on the initial hops.

- Data_TTL

This is the (non-default) IP Time-To-Live parameter
that is being supplied on the data packets. It is
needed to ensure that Path messages do not have a
scope larger than multicast data packets.

- Sender_Policy_Data

This optional parameter passes policy data for the
sender. This data may be supplied by a system
service, with the application treating it as opaque.

Braden, Zhang, et al. Expiration: August 1996 [Page 59] 61]

Internet Draft RSVP Specification February 1996

o Reserve

Call: RESERVE( session-id, [ receiver_address , ]

[ CONF_flag, ] style, style-dependent-parms )

A receiver uses this call to make or to modify a resource
reservation for the session registered as `session-id'.
The first RESERVE call will initiate the periodic
transmission of RESV Resv messages. A later RESERVE call may
be given to modify the parameters of the earlier call (but
note that changing existing reservations may result in
admission control failures).

The optional `receiver_address' parameter may be used by a
receiver on a multihomed host (or router); it is the IP
address of one of the node's interfaces. The CONF_flag
should be set on if a reservation confirmation is desired,
off otherwise. The `style' parameter indicates the
reservation style. The rest of the parameters depend upon
the style; generally these will include appropriate
flowspecs, filter specs, and possibly receiver policy data
objects.

The RESERVE call returns immediately. Following a RESERVE
call, an asynchronous ERROR/EVENT upcall may occur at any
time.

o Release

Call: RELEASE( session-id )

This call removes RSVP state for the session specified by
session-id. The node then sends appropriate teardown
messages and ceases sending refreshes for this session-id.

o Error/Event Upcalls

The general form of a upcall is as follows:

Upcall: <Upcall_Proc>( ) -> session-id, Info_type,

information_parameters

Here "Upcall_Proc" represents the upcall procedure whose
address was supplied in the SESSION call. This upcall may

Braden, Zhang, et al. Expiration: August 1996 [Page 60] 62]

Internet Draft RSVP Specification February 1996

occur asynchronously at any time after a SESSION call and
before a RELEASE call, to indicate an error or an event.

Currently there are five upcall types, distinguished by
the Info_type parameter. The selection of information
parameters depends upon the type.

1. Info_type = PATH_EVENT

A Path Event upcall results from receipt of the first
PATH
Path message for this session, indicating to a
receiver application that there is at least one
active sender.

Upcall: <Upcall_Proc>( ) -> session-id,

Info_type=PATH_EVENT,

flags,

Sender_Tspec, Sender_Template,

[ , Advert ] [ , Policy_data ]

This upcall presents the Sender_Tspec and the
Sender_Template from a PATH Path message; it also passes
the advertisement and policy data if they are
present. The possible flags correspond to Non_RSVP
and Maybe_RSVP flags of the SESSION object.

2. Info_type = RESV_EVENT

A Resv Event upcall is triggered by the receipt of
the first RESV message, or by modification of a
previous reservation state, for this session.

Upcall: <Upcall_Proc>( ) -> session-id,

Info_type=RESV_EVENT,

Style, Flowspec, Filter_Spec_list,

[ , Policy_data ]

Here `Flowspec' will be the effective QoS that has
been received. Note that an FF-style RESV Resv message

Braden, Zhang, et al. Expiration: August 1996 [Page 61] 63]

Internet Draft RSVP Specification February 1996

may result in multiple RESV_EVENT upcalls, one for
each flow descriptor.

3. Info_type = PATH_ERROR

An Path Error event indicates an error in sender
information that was specified in a SENDER call.

Upcall: <Upcall_Proc>( ) -> session-id,

Info_type=PATH_ERROR,

Error_code , Error_value ,

Error_Node , Sender_Template,

[ Policy_data Policy_data_list ]

The Error_code parameter will define the error, and
Error_value may supply some additional (perhaps
system-specific) data about the error. The
Error_Node parameter will specify the IP address of
the node that detected the error. The Policy_data
Policy_data_list parameter, if present, will contain the
any POLICY_DATA
object objects from the failed PATH Path message.

4. Info_type = RESV_ERR

An Resv Error event indicates an error in a
reservation message to which this application
contributed.

Upcall: <Upcall_Proc>( ) -> session-id,

Info_type=RESV_ERROR,

Error_code , Error_value ,

Error_Node , Error_flags ,

Flowspec, Filter_spec_list,

[ Policy_data Policy_data_list ]

The Error_code parameter will define the error and
Error_value may supply some additional (perhaps

Braden, Zhang, et al. Expiration: August 1996 [Page 62] 64]

Internet Draft RSVP Specification February 1996

system-specific) data. The Error_Node parameter will
specify the IP address of the node that detected the
event being reported.

There are two Error_flags:

- InPlace

This flag may be on for an Admission Control
failure, to indicate that there was, and is, a
reservation in place at the failure node. This
flag is set at the failure point and forwarded
in RERR ResvErr messages.

- NotGuilty

This flag may be on for an Admission Control
failure, to indicate that the flowspec requested
by this receiver was strictly less than the
flowspec that got the error. This flag is set
at the receiver API.

Filter_spec_list and Flowspec will contain the
corresponding objects from the error flow descriptor
(see Section 3.1.6). List_count will specify the
number of FILTER_SPECS in Filter_spec_list. The
Policy_data _list parameter will contain any
POLICY_DATA objects in from the RERR ResvErr message.

5. Info_type = RESV_CONFIRM

A Confirmation event indicates that a RACK ResvConf
message was received.

Upcall: <Upcall_Proc>( ) -> session-id,

Info_type=RESV_CONFIRM,

Style, List_count,

Flowspec, Filter_spec_list,

[ Policy_data ]

The parameters are interpreted as in the Resv Error
upcall.

Braden, Zhang, et al. Expiration: August 1996 [Page 63] 65]

Internet Draft RSVP Specification February 1996

Although RSVP messages indicating path or resv events may
be received periodically, the API should make the
corresponding asynchronous upcall to the application only
on the first occurrence or when the information to be
reported changes. All error and confirmation events
should be reported to the application.

3.10.2 RSVP/Traffic Control Interface

In an RSVP-capable node, enhanced QoS is achieved by a group of
inter-related traffic control functions: a packet classifier,
an admission control module, and a packet scheduler. This
section describes a generic RSVP interface to traffic control.

o Make a Reservation

Call: Rhandle = TC_AddFlowspec( Interface, TC_Flowspec,

TC_Tspec, Police_Flags )

The TC_Flowspec parameter defines the desired effective
QoS to admission control; its value is computed as the
maximum over the flowspecs of different next hops (see the
Compare_Flowspecs call below). It contains the effective
reservation Tspec Resv_Te (although the RSVP daemon itself
has no means to extract the Tspec). The TC_Tspec
parameter defines the effective sender Tspec Path_Te (see
Section 2.3). We assume that traffic control takes the
GLB of Resv_Te and Path_Te (see step (4) in Section 2.3).
The Police_Flags parameter carries the three flags
E_Police_Flag, M_Police_Flag, and B_Police_Flag; see
Section 3.7.

The TC_AddFlowspec call returns an error code if Flowspec
is malformed or if the requested resources are
unavailable. Otherwise, it establishes a new reservation
channel corresponding to Rhandle. It returns the opaque
number Rhandle for subsequent references to this
reservation.

o Modify Reservation

Call: TC_ModFlowspec( Interface, Rhandle, new_Flowspec,

Sender_Tspec, Police_flags )

Braden, Zhang, et al. Expiration: August 1996 [Page 64] 66]

Internet Draft RSVP Specification February 1996

This call is used to modify an existing reservation.
New_Flowspec is passed to Admission Control; if it is
rejected, the current flowspec is left in force. The
corresponding filter specs, if any, are not affected. The
other parameters are defined as in TC_AddFlowspec.

o Delete Flowspec

Call: TC_DelFlowspec( Interface, Rhandle )

This call will delete an existing reservation, including
the flowspec and all associated filter specs.

o Add Filter Spec

Call: FHandle = TC_AddFilter( Interface, Rhandle,

Session , FilterSpec )

This call is used to associate an additional filter spec
with the reservation specified by the given Rhandle,
following a successful TC_AddFlowspec call. This call
returns a filter handle FHandle.

o Delete Filter Spec

Call: TC_DelFilter( Interface, FHandle )

This call is used to remove a specific filter, specified
by FHandle.

o OPWA Update

Call: TC_Advertise( Interface, Adspec )

-> New_Adspec

This call is used for OPWA to compute the outgoing
advertisement New_Adspec for a specified interface.

o Preemption Upcall

Upcall: TC_Preempt() -> RHandle, Reason_code

Braden, Zhang, et al. Expiration: August 1996 [Page 65] 67]

Internet Draft RSVP Specification February 1996

In order to grant a new reservation request, the admission
control and/or policy modules may preempt an existing
reservation. This might be reflected in an upcall to
RSVP, passing the RHandle of the preempted reservation and
a sub-code indicating the reason.

3.10.3 RSVP/Routing Interface

An RSVP implementation needs the following support from the
packet forwarding and routing mechanisms of the node.

o Promiscuous Receive Mode for RSVP Messages

Packets received for IP protocol 46 but not addressed to
the node must be diverted to the RSVP program for
processing, without being forwarded. On a router, the
identity of the interface, real or virtual, on which it is
received as well as the IP source address and IP TTL with
which it arrived must also be available to the RSVP
daemon.

The RSVP messages to be diverted will carry the Router
Alert IP option, which can be used to pick them out of a
high-speed forwarding path. Alternatively, the node can
intercept all protocol 46 packets.

When an RSVP message (fragment) is handed to RSVP, the
actual length received must also be passed.

o Route Query

To forward PATH Path and PTEAR PathTear messages, an RSVP daemon must
be able to query the routing daemon(s) for routes.

Ucast_Route_Query( [ SrcAddress, ] DestAddress,

Notify_flag ) -> OutInterface

Mcast_Route_Query( [ SrcAddress, ] DestAddress,

Notify_flag )

-> [ IncInterface, ] OutInterface_list

Depending upon the routing protocol, the query may or may
not depend upon SrcAddress, i.e., upon the sender host IP
address, which is also the IP source address of the

Braden, Zhang, et al. Expiration: August 1996 [Page 68]

Internet Draft RSVP Specification February 1996

message. Here IncInterface is the interface through which
the packet is expected to arrive; some multicast routing
protocols may not provide it. If the Notify_flag is True,
routing will save state necessary to issue unsolicited
route change notification callbacks (see below) whenever
the specified route changes.

Braden, Zhang, et al. Expiration: August 1996 [Page 66]

Internet Draft RSVP Specification February 1996

A multicast route query may return an empty
OutInterface_list if there are no receivers downstream of
a particular router. A route query may also return a `No
such route' error, probably as a result of a transient
inconsistency in the routing (since a PATH Path or PTEAR PathTear
message for the requested route did arrive at this node).
In either case, the local state should be updated as
requested by the message, which cannot be forwarded
further. Updating local state will make path state
available immediately for a new local receiver, or it will
tear down path state immediately.

o Route Change Notification

If requested by a route query with the Notify_flag True,
the routing daemon may provide an asynchronous callback to
the RSVP daemon that a specified route has changed.

Ucast_Route_Change( ) -> [ SrcAddress, ] DestAddress,

OutInterface

Mcast_Route_Change( ) -> [ SrcAddress, ] DestAddress,

[ IncInterface, ] OutInterface_list

o Outgoing Link Specification

RSVP must be able to force a (multicast) datagram to be
sent on a specific outgoing virtual link, bypassing the
normal routing mechanism. A virtual link may be a real
outgoing link or a multicast tunnel. Outgoing link
specification is necessary to send different versions of
an outgoing PATH Path message on different interfaces. It is
also necessary in some cases to avoid routing loops.

o Source Address Specification

RSVP must be able to specify the IP source address to be
used when sending PATH Path messages.

Braden, Zhang, et al. Expiration: August 1996 [Page 69]

Internet Draft RSVP Specification February 1996

o Interface List Discovery

RSVP must be able to learn what real and virtual
interfaces are active, with their IP addresses.

It should be possible to logically disable an interface

Braden, Zhang, et al. Expiration: August 1996 [Page 67]

Internet Draft RSVP Specification February 1996
for RSVP. When an interface is disabled for RSVP, a PATH Path
message should never be forwarded out that interface, and
if an RSVP message is received on that interface, the
message should be silently discarded (perhaps with local
logging).

3.10.4 Service-Dependent Manipulations

Flowspecs, Tspecs, and Adspecs are opaque objects to RSVP;
their contents are defined in service specification documents.
In order to manipulate these objects, RSVP daemon must have
available to it the following service-dependent routines.

o Compare Flowspecs

Compare_Flowspecs( Flowspec_1, Flowspec_2 ) ->

result_code

The possible result_codes indicate: flowspecs are equal,
Flowspec_1 is greater, Flowspec_2 is greater, flowspecs
are incomparable but LUB can be computed, or flowspecs are
incompatible.

Note that comparing two flowspecs implicitly compares the
Tspecs that are contained. Although the RSVP daemon
cannot itself parse a flowspec to extract the Tspec, it
can use the Compare_Flowspecs call to implicitly calculate
Resv_Te (see Section 2.3).

o Compute LUB of Flowspecs

LUB_of_Flowspecs( Flowspec_1, Flowspec_2 ) ->

Flowspec_LUB

o Compute GLB of Flowspecs

Braden, Zhang, et al. Expiration: August 1996 [Page 70]

Internet Draft RSVP Specification February 1996

GLB_of_Flowspecs( Flowspec_1, Flowspec_2 ) ->

Flowspec_GLB

o Compare Tspecs

Compare_Tspecs( Tspec_1, Tspec_2 ) -> result_code

Braden, Zhang, et al. Expiration: August 1996 [Page 68]

Internet Draft RSVP Specification February 1996

The possible result_codes indicate: Tspecs are equal, or
Tspecs are unequal.

o Sum Tspecs

Sum_Tspecs( Tspec_1, Tspec_2 ) -> Tspec_sum

This call is used to compute Path_Te (see Section 2.3).

Braden, Zhang, et al. Expiration: August 1996 [Page 69] 71]

Internet Draft RSVP Specification February 1996

4. Message Processing Rules

This section provides a generic description of the rules for RSVP
operation. It is intended to outline a set of algorithms that will
accomplish the needed function, omitting some details.

This section assumes the generic interface calls defined in Section
3.10 and the following data structures. An actual implementation may
use additional or different data structures and interfaces. The data
structure fields that a shown are required unless they are explicitly
labelled as optional.

o PSB -- Path State Block

Each PSB holds path state for a particular (session, sender)
pair, defined by SESSION and SENDER_TEMPLATE objects,
respectively, received in a PATH Path message.

PSB contents include the following values from a PATH Path message:

- Session

- Sender_Template

- Sender_Tspec

- The previous hop IP address and the Logical Interface
Handle (LIH) from a PHOP object

- The remaining IP TTL

- POLICY_DATA and/or ADSPEC objects (optional)

- Non_RSVP and Maybe_RSVP flags; see Section 3.7.

- E_Police flag (Section 3.7)

- Local_Only flag (Section 3.8)

In addition, the PSB contains the following information provided
by routing: OutInterface_list, which is the list of outgoing
interfaces for this (sender, destination), and IncInterface,
which is the expected incoming interface. For a unicast
destination, OutInterface_list contains one entry and
IncInterface is undefined.

o RSB -- Reservation State Block

Braden, Zhang, et al. Expiration: August 1996 [Page 70] 72]

Internet Draft RSVP Specification February 1996

Each RSB holds a reservation request that arrived in a
particular RESV Resv message, corresponding to the triple: (session,
next hop, Filter_spec_list). Here "Filter_spec_list" may be a
list of FILTER_SPECs (for SE style), a single FILTER_SPEC (FF
style), or empty (WF style). We define a virtual object type
"FILTER_SPEC*" for such a data structure.

RSB contents include:

- Session specification

- Next hop IP address

- Filter_spec_list

- The outgoing (logical) interface OI on which the
reservation is to be made or has been made (required).

- Style

- Flowspec

- A POLICY_DATA object (optional)

- A SCOPE object (optional, depending on style)

- A RESV_CONFIRM object (optional)

o TCSB -- Traffic Control State Block

Each TCSB holds the reservation specification that has been
handed to traffic control for a specific outgoing interface. In
general, TCSB information is derived from RSB's for the same
outgoing interface. Each TCSB defines a single reservation for
a particular triple: (session, OI, Filter_spec_list). TCSB
contents include:

- Session

- OI

- Filter_spec_list

- TC_Flowspec, the effective flowspec, i.e., the maximum over
the corresponding FLOWSPEC values from matching RSB's.
TC_Flowspec is passed to traffic control to make the actual
reservation. The Tspec part of TC_Flowspec is the
effective reservation Tspec Resv_Te (Section 2.3).

Braden, Zhang, et al. Expiration: August 1996 [Page 71] 73]

Internet Draft RSVP Specification February 1996

- TC_Tspec, equal to Path_Te, the effective sender Tspec.

- Police Flags

The flags E_Police_Flag, M_Police_Flag, and B_Police_Flag
are defined in Section 3.7.

- Rhandle, F_Handle_list

Handles returned by the traffic control interface,
corresponding to the reservation (flowspec) and to the list
of filter specs.

o BSB -- Blockade State Block

Each BSB contains an element of blockade state. Depending upon
the reservation style in use, the BSB's may be per (session,
sender_template) or per (session, PHOP). In practice, an
implementation might embed a BSB within a PSB; however, for
clarity we describe BSB's independently.

The contents of a BSB include:

- Session

- Sender_Template (which is also a filter spec)

- PHOP

- FLOWSPEC Qb

- Blockade timer Tb

The following other variables are also used in this section: Boolean
flags Path_Refresh_Needed, Resv_Refresh_Needed, Tear_Needed,
Need_Scope, B_Merge, and NeworMod, and Refresh_PHOP_list, a
variable-length list of PHOPs to be refreshed.

MESSAGE ARRIVES

Verify version number and RSVP checksum, and discard message if any
mismatch is found.

If the message type is not PATH Path or PTEAR PathTear and if the IP destination
address does not match any of the addresses of the local interfaces,
then forward the message to IP destination address and return.

Verify the INTEGRITY object, if any. If the check fails, discard the

Braden, Zhang, et al. Expiration: August 1996 [Page 72] 74]

Internet Draft RSVP Specification February 1996

message and return.

Reassemble fragments of message.

Parse the sequence of objects in the message, and discard message if
any required objects are missing. Verify the length field of the
common header, and discard message if there is a mismatch.

Verify the consistent use of port fields. If the DstPort in the
SESSION object is zero but the SrcPort in a SENDER_TEMPLATE or
FILTER_SPEC object is non-zero, the the message has a "conflicting
source port" error; discard the message and return.

Further processing depends upon message type.

PATH

Path MESSAGE ARRIVES

Process the sender descriptor object sequence in the message as
follows. The Path_Refresh_Needed and Resv_Refresh_Needed flags
are initially off.

o If there is a POLICY_DATA object, verify it; if it is
unacceptable, build and send a "Administrative Rejection"
PERR
PathErr message, drop the PATH Path message, and return.

o Search for a path state block (PSB) whose (session,
sender_template) pair matches the corresponding objects in
the message.

o If, during the PSB search, a PSB is found whose session
matches the DestAddress and Protocol Id fields of the
received SESSION object, but the DstPorts differ and one is
zero, then build and send a "Conflicting Dst Port" PERR PathErr
message, drop the PATH Path message, and return.

o If, during the PSB search, a PSB is found with a matching
sender host but the SrcPorts differ and one of the SrcPorts
is zero, then build and send an "Ambiguous Path" PERR PathErr
message, drop the PATH Path message, and return.

o If there was no matching PSB, then:

1. Create a new PSB.

2. Copy contents of the SESSION, SENDER_TEMPLATE,
SENDER_TSPEC, and PHOP (IP address and LIH) objects
into the PSB.

Braden, Zhang, et al. Expiration: August 1996 [Page 73] 75]

Internet Draft RSVP Specification February 1996

3. Calculate initial routing information. If the sender
is from the local API, OutInterface_List is set to the
single interface whose address matches the sender
address, and IncInterface is undefined. Otherwise,
call the appropriate Route_Query routine, using
DestAddress from SESSION and (for multicast routing)
SrcAddress from SENDER_TEMPLATE. Store the values of
OutInterface_list and IncInterface into the PSB.

4. If IncInterface is defined and if a multicast message
arrived on an interface different from IncInterface,
turn on the Local_Only flag in the PSB.

5. If this is the first PSB for the session, set a
refresh timer for the session.

6. Turn on the Path_Refresh_Needed flag.

o Otherwise (there is a matching PSB and there is no dest
port conflict):

1. If there is no route change notification in place,
call the appropriate Route_Query routine using
DestAddress from SESSION and (for multicast routing)
SrcAddress from Sender_Template.

- If the OutInterface_list that is returned differs
from that in the PSB, then execute the PATH Path LOCAL
REPAIR event sequence below.

- If a multicast message arrived on an interface
different from IncInterface, then execute the
RESV
Resv REFRESH event sequence below for the
previous hop.

2. If the PHOP IP address, the LIH, or Sender_Tspec
differs between the message and the PSB, copy the new
value into the PSB and turn on the Path_Refresh_Needed
flag.

o If the message contains an ADSPEC object, copy it into the
PSB.

o Start or Restart the cleanup timer for the PSB.

o Copy E_Police flag from SESSION object into PSB.

o Store the received TTL into the PSB.

Braden, Zhang, et al. Expiration: August 1996 [Page 74] 76]

Internet Draft RSVP Specification February 1996

If the the received TTL differs from Send_TTL in the RSVP
common header, set the Non_RSVP flag on in the PSB.

o The Path_Refresh_Needed flag is now set if the path state
is new or modified. If so:

1. If this PATH Path message came from a network interface and
not from a local application, make a Path Event upcall
for each local application for this session:

Call: <Upcall_Proc>( session-id, PATH_EVENT,
flags, sender_tspec, sender_template,
[ADSPEC], [POLICY_DATA] )

2. Execute the PATH Path REFRESH event sequence (below) for
the sender defined by the PSB.

3. If there is no reservation state for this SESSION
(i.e., no RSB's exist), then drop the PATH Path message and
return.

4. Otherwise (there is reservation state):

- Execute the event sequence UPDATE TRAFFIC CONTROL
below, to update the local traffic control state
if necessary. This will turn on the
Resv_Refresh_Needed flag if the traffic control
state changes; if so, execute the RESV Resv REFRESH
event sequence (below) for the sender in the PSB.

However, if the PATH Path message came from a local
application, then make a RESV_EVENT upcall to
that application.

o Drop the PATH Path message and return.

PATH TEAR

PathTear MESSAGE ARRIVES

o Search for a PSB whose (Session, Sender_Template) pair
matches the corresponding objects in the message. If no
matching PSB is found, drop the PTEAR PathTear message and
return.

o Forward a copy of the PTEAR PathTear message to each outgoing
interface listed in OutInterface_list of the PSB.

o Find each RSB that matches this PSB, i.e., that whose

Braden, Zhang, et al. Expiration: August 1996 [Page 75] 77]

Internet Draft RSVP Specification February 1996

o Find each RSB that matches this PSB, i.e., that whose
Filter_spec_list matches Sender_Template in the PSB and
whose OI is included in OutInterface_list.

If this RSB matches no other PSB, then tear down the RSB,
as described below under RESV TEAR ResvTear MESSAGE ARRIVES.

o Delete the PSB.

o Drop the PTEAR PathTear message and return.

PATH ERROR

PathErr MESSAGE ARRIVES

o Search for a PSB whose (SESSION, SENDER_TEMPLATE) pair
matches the corresponding objects in the message. If no
matching PSB is found, drop the PERR PathErr message and return.

o If the previous hop address in the PSB is the local API,
make an error upcall to the application:

Call: <Upcall_Proc>( session-id, PATH_ERROR,
Error_code, Error_value,
Node_Addr, Sender_Template,
[Policy_Data] )

Any SENDER_TSPEC or ADSPEC object in the message is
ignored.

Otherwise, send a copy of the PERR PathErr message to the PHOP
IP address.

o Drop the PERR PathErr message and return.

RESV

Resv MESSAGE ARRIVES

Initially, Refresh_PHOP_list is empty and the
Resv_Refresh_Needed and NeworMod flags are off. These variables
are used to control immediate reservation refreshes.

o Determine the Outgoing Interface OI

The logical outgoing interface OI is taken from the LIH in
the NHOP object. (If the physical interface is not implied
by the LIH, it can be learned from the interface matching
the IP destination address).

Braden, Zhang, et al. Expiration: August 1996 [Page 76] 78]

Internet Draft RSVP Specification February 1996

o Check the SESSION object.

If there are no existing PSB's for SESSION then build and
send a RERR ResvErr message (as described later) specifying "No
path information", drop the RESV Resv message, and return.

o Check the S_POLICY_DATA object.

If there is an S_POLICY_DATA object in the message, check
permission to create a reservation for the session. If the
check fails, build and send an "Administrative rejection"
RERR
ResvErr message, drop the RESV Resv message, and return.
Otherwise, copy the S_POLICY_DATA object into the RSB.

o Check for incompatible styles.

If any existing RSB for the session has a style that is
incompatible with the style of the message, build and send
a RERR ResvErr message specifying "Conflicting Style", drop the
RESV
Resv message, and return.

Process the flow descriptor list to make reservations, as
follows, depending upon the style. The following uses a filter
spec list struct Filtss, of type FILTER_SPEC* (defined earlier).

For FF style: execute the following steps independently for each
flow descriptor in the message, i.e., for each (FLOWSPEC,
Filtss) pair. Here the structure Filtss consists of the
FILTER_SPEC from the flow descriptor.

For SE style, execute the following steps once for (FLOWSPEC,
Filtss), with Filtss consisting of the list of FILTER_SPEC
objects from the flow descriptor.

For WF style, execute the following steps once for (FLOWSPEC,
Filtss), with Filtss an empty list.

o If the DstPort in the SESSION object is zero but the
SrcPort in a FILTER_SPEC object (in Filtss) is non-zero,
build nd send a "Conflicting Src Port" RERR ResvErr message,
drop the RESV Resv message, and return.

o Check the path state, as follows.

1. Locate the set of PSBs (senders) whose
SENDER_TEMPLATEs match Filtss and whose
OutInterface_list includes OI.

Braden, Zhang, et al. Expiration: August 1996 [Page 77] 79]

Internet Draft RSVP Specification February 1996

If this set is empty, build and send an error message
specifying "No sender information", and continue with
the next flow descriptor in the RESV Resv message.

2. If the style has explicit sender selection (e.g., FF
or SE) and if any FILTER_SPEC included in Filtss
matches more than one PSB, build and send a RERR ResvErr
message specifying "Ambiguous filter spec" and
continue with the next flow descriptor in the RESV Resv
message.

3. Add the PHOP from the PSB to Refresh_PHOP_list, if the
PHOP is not already on the list.

o Find or create a reservation state block (RSB) for the
triple: (session, NHOP, Filtss). Call this the "active
RSB".

o If the active RSB is new:

1. Set the session, NHOP, OI and style of the RSB from
the message.

2. Copy Filtss into the Filter_spec_list of the RSB.

3. Copy the FLOWSPEC and any SCOPE object from the
message into the RSB.

4. Set NeworMod flag on.

o Start or restart the cleanup timer on the the active RSB.

o If there is a RESV_CONFIRM in the message, turn on
Resv_Refresh_Needed and save the object in the RSB.

o If the active RSB is not new, check whether STYLE, FLOWSPEC
or SCOPE objects have changed; if so, copy changed object
into RSB and turn on the NeworMod flag.

o If NeworMod flag is off, continue with the next flow
descriptor in the RESV Resv message, if any.

o Otherwise (the NeworMod flag is on, i.e., the active RSB is
new or modified), execute the UPDATE TRAFFIC CONTROL event
sequence (below). If the result is to modify the traffic
control state, it will turn on the Resv_Refresh_Needed
flag.

Braden, Zhang, et al. Expiration: August 1996 [Page 78] 80]

Internet Draft RSVP Specification February 1996

o For any local sender, make an RESV_EVENT upcall to the
application:

Call: <Upcall_Proc>( session-id, RESV_EVENT,
style, Flowspec, Filter_spec_list,
[POLICY_DATA] )

where the parameters come from the active RSB.

o Continue with the next flow descriptor.

o When all flow descriptors have been processed, check the
Resv_Refresh_Needed flag. If it is now on, execute the
RESV
Resv REFRESH sequence (below) for each PHOP in
Refresh_PHOP_list.

o Drop the RESV Resv message and return.

If processing a RESV Resv message finds an error, a RERR ResvErr message
is created containing flow descriptor and an ERRORS object. The
Error Node field of the ERRORS object is set to the IP address
of OI, and the message is sent unicast to NHOP.

RESV TEAR

ResvTear MESSAGE ARRIVES

A RTEAR ResvTear message arrives with an IP destination address
matching outgoing interface OI. Flags Tear_Needed and
Resv_Refresh_Needed are initially off and Refresh_PHOP_list is
empty.

o Process the STYLE object and the flow descriptor list in
the RTEAR ResvTear message to tear down local reservation state,
as follows.

The following uses We assume a filter spec list struct Filtss, of
type FILTER_SPEC* (defined earlier).

For FF style: execute the following steps independently for
each flow descriptor in the message, i.e., for each
(FLOWSPEC, Filtss) pair. Here the structure Filtss
consists of the FILTER_SPEC from the flow descriptor.

For SE style, execute the following steps once for
(FLOWSPEC, Filtss), with Filtss consisting of the list of
FILTER_SPEC objects from the flow descriptor.

For WF style, execute the following steps once for
(FLOWSPEC, Filtss), with Filtss an empty list.

Braden, Zhang, et al. Expiration: August 1996 [Page 79] 81]

Internet Draft RSVP Specification February 1996

(FLOWSPEC, Filtss), with Filtss an empty list.

1. Find matching RSB for the triple: (SESSION, NHOP,
Filtss); call this the active RSB. If no active RSB
is found, continue with next flow descriptor.

2. Delete the active RSB.

3. Execute the event sequence UPDATE TRAFFIC CONTROL
(below) to update the traffic control state to be
consistent with the reservation state.

4. Search for a TCSB remaining for the (session, OI,
Filtss) triple; if not, set the Tear_Needed flag on.

5. Continue with the next flow descriptor.

o If Tear_Needed and Resv_Refresh_Needed flags are both off,
then drop the RTEAR ResvTear message and return.

o If Tear_Needed is off but Resv_Refresh_Needed is on, then
execute the RESV Resv REFRESH sequence for each PHOP in
Refresh_PHOP_list, drop the RTEAR ResvTear message, and return.

o Otherwise (Tear_Needed is on), need to forward RTEAR ResvTear
and/or
RESV Resv refresh messages.

Do the following for each PSB whose OutInterface_list
includes the outgoing interface OI:

1. Pick each flow descriptor Fj in the RTEAR ResvTear message
whose FILTER_SPEC matches the PSB, and do the
following.

- If there is no RSB whose FILTER_SPEC matches the
PSB, then add Fj to the new RTEAR ResvTear message
being built.

- Otherwise (there is a matching RSB), note the PSB
as needing a RESV Resv refresh message and set the
Resv_Refresh_Needed flag True.

2. If the new RTEAR ResvTear message contains any flow
descriptors, send it to PHOP in the PSB.

o If the Resv_Refresh_Needed flag is now on, execute the RESV
REFRESH sequence (below) for each PHOP in
Refresh_PHOP_list.

o Drop the ResvTear message and return.

Braden, Zhang, et al. Expiration: August 1996 [Page 80] 82]

Internet Draft RSVP Specification February 1996

o Drop the RTEAR message and return.

RESV ERROR

ResvErr MESSAGE ARRIVES

A RERR ResvErr message arrives through the (real) incoming interface
In_If.

o If there is no path state for SESSION, drop the RERR ResvErr
message and return.

o If the Error Code = 01 (Admission Control failure), do
special processing as follows:

1. Find or create a Blockade State Block (BSB), in the
following style-dependent manner.

For WF (wildcard) style, there will be one BSB per
(session, PHOP) pair.

For FF style, there will be one BSB per (session,
filter_spec) pair. Note that an FF style RERR ResvErr
message carries only one flow descriptor.

For SE style, there will be one BSB per (session,
filter_spec), for each filter_spec contained in the
filter spec list of the flow descriptor.

2. For each BSB in the preceding step, set (or replace)
its FLOWSPEC Qb with FLOWSPEC from the message, and
set (or reset) its timer Tb to Kb*R seconds [Section
3.4]. If the BSB is new, set its PHOP value, and set
its Sender_Template equal to the appropriate
filter_spec from the message.

3. Partially execute the RESV Resv REFRESH event sequence
shown below, for the previous hop PHOP.

In particular, execute the refresh sequence with the
B_Merge flag off. If this results in no refresh
messages being generated, because all matching
reservations are blockaded, do not turn B_Merge on but
instead exit the refresh sequence and return here.

o For all RERR ResvErr messages, execute the following for each
RSB for this session whose OI differs from In_If and whose
Filter_spec_list has at least one filter spec in common
with the FILTER_SPEC* in the RERR ResvErr message. For WF
style,

Braden, Zhang, et al. Expiration: August 1996 [Page 81]

Internet Draft RSVP Specification February 1996 empty FILTER_SPEC* structures are assumed to match.

1. If Error_Code = 01 and the InPlace flag is 1 and one

Braden, Zhang, et al. Expiration: August 1996 [Page 83]

Internet Draft RSVP Specification February 1996

or more of the BSB's found/created above has a Qb that
is strictly greater than Flowspec in the RSB, then
continue with the next matching RSB, if any.

2. If NHOP in the RSB is the local API, then:

- If the FLOWSPEC in the RERR ResvErr message is
strictly greater than the RSB Flowspec, then turn
on the NotGuilty flag in the ERROR_SPEC.

- Deliver an error upcall to application:

Call: <Upcall_Proc>( session-id, RESV_ERROR,
Error_code, Error_value,
Node_Addr, Error_flags,
Flowspec, Filter_Spec_List,
[Policy_data] )

and continue with the next RSB.

3. If the style has wildcard sender selection, use the
SCOPE object SC.In from the RERR ResvErr message to
construct a SCOPE object SC.Out to be forwarded.
SC.Out should contain those sender addresses that
appeared in SC.In and that route to OI [LIH?], as
determined by scanning the PSB's. If SC.Out is empty,
continue with the next RSB.

4. Create a new RERR ResvErr message containing the error flow
descriptor and send to the NHOP address specified by
the RSB. Include SC.Out if the style has wildcard
sender selection.

5. Continue with the next RSB.

o Drop the RERR ResvErr message and return.

RESV

Resv CONFIRM ARRIVES

o If the (unicast) IP address found in the RESV_CONFIRM
object in the RACK ResvConf message matches an interface of the
node, a confirmation upcall is made to the matching
application:

Braden, Zhang, et al. Expiration: August 1996 [Page 82] 84]

Internet Draft RSVP Specification February 1996

application:

Call: <Upcall_Proc>( session-id, RESV_CONFIRM,
Error_code, Error_value, Node_Addr,
LUB-Used, nlist, Flowspec,
Filter_Spec_List, NULL, NULL )

o Otherwise, the RACK ResvConf message is forwarded immediately to
the address in the IP address in its RESV_CONFIRM object.

o Drop the RACK ResvConf message and return.

UPDATE TRAFFIC CONTROL

The sequence is invoked by the PATH Path MESSAGE ARRIVES or the RESV Resv
MESSAGE ARRIVES sequence, to (re-)calculate and adjust the local
traffic control state in accordance with the current reservation
and path state. If the result is to modify the traffic control
state, this sequence turns on the Resv_Refresh_Needed flag.

o Compute the traffic control parameters using the following
steps.

1. Consider the set of RSB's matching SESSION and OI from
the message.

- Compute the effective kernel flowspec,
TC_Flowspec, as the maximum/LUB of the FLOWSPEC
values in these RSB's.

- Compute the effective traffic control filter spec
(list) TC_Filter_Spec*, by merging the
Filter_spec_lists from these RSB's.

2. Scan all RSB's matching session and Filtss, for all
OI. Set TC_B_Police_flag on if TC_Flowspec is smaller
than, or incomparable to, any FLOWSPEC in those RSB's.

3. Locate the set of PSBs (senders) whose
SENDER_TEMPLATEs match Filter_spec_list in the active
RSB and whose OutInterface_list includes OI.

4. Set TC_E_Police_flag on if any of these PSBs have
their E_Police flag on. Set TC_M_Police_flag on if it
is a shared style and there is more than one PSB in
the set.

5. Compute Path_Te as the sum of the SENDER_TSPEC objects

Braden, Zhang, et al. Expiration: August 1996 [Page 83] 85]

Internet Draft RSVP Specification February 1996

the set.

5. Compute Path_Te as the sum of the SENDER_TSPEC objects

in this set of PSBs.

o Search for a TCSB matching SESSION and OI; for distinct
style (FF), it must also match Filter_spec_list.

If none is found, create a new TCSB.

o If TCSB is new:

1. Store TC_Flowspec, TC_Filter_Spec*, Path_Te, and the
police flags into TCSB.

2. Turn the Resv_Refresh_Needed flag on and make the
traffic control call:

Rhandle = TC_AddFlowspec( OI, TC_Flowspec,
Path_Te, police_flags)

3. If this call succeeds, record Rhandle in the TCSB and,
for each filter_spec F in TC_Filter_Spec*, call:

Fhandle = TC_AddFilter( OI, Rhandle, Session, F)

and record the returned Fhandle in the TCSB.

4. Otherwise, build and send a RERR ResvErr message specifying
"Admission control failed" and with the InPlace flag
off.

o If TCSB is not new but the TC_Flowspec, Path_Te, and/or
police flags just computed differ from corresponding values
in the TCSB, then:

1. Turn the Resv_Refresh_Needed flag on and make the
traffic control call:

TC_ModFlowspec( OI, Rhandle, TC_Flowspec,
Path_Te, police_flags )

2. If this call fails, build and send a RERR ResvErr message

Braden, Zhang, et al. Expiration: August 1996 [Page 84]

Internet Draft RSVP Specification February 1996
specifying "Admission control failed" and with the
InPlace bit on. If the call succeeds, update the TCSB
with the new values.

Braden, Zhang, et al. Expiration: August 1996 [Page 86]

Internet Draft RSVP Specification February 1996

o If the TCSB is not new but the TC_Filter_Spec* just
computed differ from the FILTER_SPEC* in the TCSB, then:

1. Make an appropriate set of TC_DelFilter and
TC_AddFilter calls to transform the Filter_spec_list
in the TCSB into the new TC_Filter_Spec*.

o Return to the event sequence that invoked this one.

PATH

Path REFRESH

This sequence sends a path refresh for a particular sender,
i.e., a PSB. This sequence may be entered by either the
expiration of the path refresh timer or directly as the result
of the Path_Refresh_Needed flag being turned on during the
processing of a received PATH Path message.

o Compute the IP TTL for the PATH Path message as one less than
the maximum of the TTL values from the senders included in
the message. However, if the result is zero, return
without sending the PATH Path message.

o Insert TIME_VALUES and PHOP objects into the PATH Path message
being built.

o Create a sender descriptor containing the SENDER_TEMPLATE,
SENDER_TSPEC, and POLICY_DATA objects, if present in the
PSB, and pack it into the PATH Path message being built.

o Pass any ADSPEC and SENDER_TSPEC objects present in the PSB
to the traffic control call TC_Advertise. Insert the
modified ADSPEC object that is returned into the PATH Path
message being built.

o If the PSB has the E_Police flag on and if interface OI is
not capable of policing, turn the E_Police flag on in the
PATH
Path message being built.

o Send a copy of the PATH Path message to each interface in
OutInterfact_list. Before sending each copy, insert into
its PHOP object the interface address and the LIH for the
interface.

Resv REFRESH

This sequence sends a reservation refresh towards a particular

Braden, Zhang, et al. Expiration: August 1996 [Page 85] 87]

Internet Draft RSVP Specification February 1996

RESV REFRESH

This sequence sends a reservation refresh towards a particular

previous hop with IP address PH. This sequence may be entered
by either the expiration of a reservation refresh timer or
directly as a result of the Resv_Refresh_Needed flag being
turned on by processing a RESV Resv or RTEAR ResvTear message.

In general, this sequence considers each of the PSB's with PHOP
address PH. For a given PSB, it scans the RSBs for matching
reservations and merges the styles, FLOWSPECs and
Filter_spec_list's appropriately. It then builds a RESV Resv message
and sends it to PH. The details depend upon the attributes of
the style(s) included in the reservations.

o Create an output message containing INTEGRITY (if
supported), SESSION, RSVP_HOP, and TIME_VALUES objects.

o Determine the style for these reservations from the first
RSB for the session, and move the STYLE object into the
proto-message. (Note that the present set of styles are
never themselves merged; if future styles can be merged,
these rules will become more complex).

o If style is wildcard and if there are PSB's from more than
one PHOP and if the multicast routing protocol does not use
shared trees, set the Need_Scope flag on, otherwise set it
off.

o Select each sender PSB whose PHOP has address PH.

1. Set local flag B_Merge off.

2. Select all RSB's whose Filter_spec_list's match the
SENDER_TEMPLATE object in the PSB and whose OI appears
in the OutInterface_list of the PSB.

3. If B_Merge flag is off then ignore a blockaded RSB, as
follows.

- Select BSB's that match this RSB; if any of these
BSB's has a Qb that is not strictly larger than
RSB Flowspec, then continue processing with the
next RSB.

However, if steps 1 and 2 result in finding that all
RSB's matching this PSB are blockaded, then:

Braden, Zhang, et al. Expiration: August 1996 [Page 86]

Internet Draft RSVP Specification February 1996

- If this RESV Resv REFRESH sequence was invoked from
RESV ERROR RECEIVED, then return now to the
latter.

Braden, Zhang, et al. Expiration: August 1996 [Page 88]

Internet Draft RSVP Specification February 1996

- Otherwise, turn on the B_Merge flag and restart
with this procedure step 1. above.

4. Merge the flowspecs, as follows:

- If B_Merge flag is off, compute the LUB over the
Flowspec objects of this set of RSB's.

While computing the LUB, check for a RESV_CONFIRM
object in each RSB. If a RESV_CONFIRM object is
found:

- If the FLOWSPEC in that RSB is larger than
all other (non-blockaded) flowspecs being
compared, then save this RESV_CONFIRM object
for forwarding.

- Otherwise (the corresponding FLOWSPEC is not
the largest) then create and send a RACK ResvConf
message containing the RESV_CONFIRM object
to the address in the RESV_CONFIRM object.
Include the RESV_CONFIRM object in the RACK
ResvConf message. The RACK message should
also include an ERROR_SPEC object whose
Error_Node parameter is IP address of OI
from the RSB.

- Then delete the RESV_CONFIRM object from the
RSB.

- Otherwise (B_Merge flag is on), compute the GLB
over the Flowspec objects of this set of RSB's.

While computing the GLB, check for a RESV_CONFIRM
object in each RSB. If one is found, delete it.

5. If the Need_Scope flag is on, compute a new SCOPE
object as the union of the SCOPE objects found in the
RSB's.

6. Merge the F_POLICY_DATA objects from the RSB's.

7. (All matching RSB's have been processed). The next
step depends upon the style attributes.

Braden, Zhang, et al. Expiration: August 1996 [Page 87]

Internet Draft RSVP Specification February 1996

8. Merge the matching FILTER_SPEC objects from this set
of RSB's. For explicit sender selection (FF, SE)
styles, use the SENDER_TEMPLATE as the merged

Braden, Zhang, et al. Expiration: August 1996 [Page 89]

Internet Draft RSVP Specification February 1996

FILTER_SPEC; for wildcard sender selection (WF) style,
there is no filter spec to be merged.

Distinct reservation (FF) style

Use the Sender_Template as the merged
FILTER_SPEC. Pack the merged (FLOWSPEC,
FILTER_SPEC, F_POLICY_DATA) triplet into the
message as a flow descriptor.

Shared wildcard reservation (WF) style

There is no merged FILTER_SPEC. Merge (take the
maximum of) the merged FLOWSPECS from the RSB's,
across all PSB's for PH.

Shared distinct reservation (SE) style

Using the Sender_Template as the merged
FILTER_SPEC, form the union of the FILTER_SPECS
obtained from the RSB's. Merge (take the maximum
of) the merged FLOWSPECS from the RSB's, across
all PSB's for PH.

9. If the Need_Scope flag is on, remove from the merged
SCOPE object all sender addresses that do not match
the set of PSB's for PH, and all senders addresses
that are local. If the resulting set is empty, no
RESV
Resv should be forwarded to this PHOP; return.
Otherwise (set is not empty), move the new SCOPE
object into the message.

o (All PSB's have been processed). If a shared reservation
style is being built, move the final merged FLOWSPEC,
F_POLICY_DATA, and FILTER_SPEC (if SE) objects into the
message.

o If a RESV_CONFIRM object was saved earlier, copy it into
the new RESV Resv message and delete it from the RSB in which it
was found.

o Set the RSVP_HOP object in the message to contain the

Braden, Zhang, et al. Expiration: August 1996 [Page 88]

Internet Draft RSVP Specification February 1996
IncInterface address through which it will be sent and the
LIH from (one of) the PSB's.

Braden, Zhang, et al. Expiration: August 1996 [Page 90]

Internet Draft RSVP Specification February 1996

o Send the message to the address PH.

PATH

Path LOCAL REPAIR

The sequence is entered when RSVP learns from routing that the
set of outgoing interfaces for some destination (G,DstPort) has
changed.

o Wait for a delay time of W seconds [Section 3.5].

o For each session that exists for destination IP address G,
execute the PATH Path REFRESH event sequence above for each
sender (PSB) for that session.

5. Acknowledgments

The design of RSVP is based upon research performed in 1992-1993 by a
collaboration including Lixia Zhang (Xerox PARC), Deborah Estrin
(USC/ISI), Scott Shenker (Xerox PARC), Sugih Jamin (USC/Xerox PARC),
and Daniel Zappala (USC). Sugih Jamin developed the first prototype
implementation of RSVP and successfully demonstrated it in May 1993.
Shai Herzog, and later Steve Berson, continued development of RSVP
prototypes.

Since 1993, many members of the Internet research community have
contributed to the design and development of RSVP; these include (in
alphabetical order) Steve Berson, Bob Braden, Lee Breslau, Dave
Clark, Deborah Estrin, Shai Herzog, Craig Partridge, Scott Shenker,
John Wroclawski, and Daniel Zappala. In addition, a number of host
and router vendors have made valuable contributions, particularly
Fred Baker (Cisco), Mark Baugher (Intel), Don Hoffman (Sun), Steve
Jakowski (NetManage), John Krawczyk (Bay Networks), and Bill Nowicki
(SGI). Ron Frederick, Bobby Minnear, Eve Schooler, and Garrett
Wollman did early interfacing of multicast applications to RSVP.
Steve Deering, Bill Fenner, and Ajit Thyagarajan helped with the
interface between RSVP and multicast routing.

Braden, Zhang, et al. Expiration: August 1996 [Page 89] 91]

Internet Draft RSVP Specification February 1996

APPENDIX A. Object Definitions

C-Types are defined for the two Internet address families IPv4 and
IP6. To accommodate other address families, additional C-Types could
easily be defined. These definitions are contained as an Appendix,
to ease updating.

All unused fields should be sent as zero and ignored on receipt.

A.1 SESSION Class

SESSION Class = 1.

o IPv4/UDP SESSION object: Class = 1, C-Type = 1

+-------------+-------------+-------------+-------------+
| IPv4 DestAddress (4 bytes) |
+-------------+-------------+-------------+-------------+
| Protocol Id | Flags | DstPort |
+-------------+-------------+-------------+-------------+

o IP/UDP SESSION object: Class = 1, C-Type = 2

+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 DestAddress (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| Protocol Id | Flags | DstPort |
+-------------+-------------+-------------+-------------+

DestAddress

The IP unicast or multicast destination address of the
session. This field must be non-zero.

Protocol Id

The IP Protocol Identifier for the data flow. This field
must be non-zero.

Braden, Zhang, et al. Expiration: August 1996 [Page 90] 92]

Internet Draft RSVP Specification February 1996

Flags

0x01 = E_Police flag

The E_Police flag is used in PATH Path messages to determine
the effective "edge" of the network, to control traffic
policing. If the sender host is not itself capable of
traffic policing, it will set this bit on in PATH Path
messages it sends. The first node whose RSVP is capable
of traffic policing will do so (if appropriate to the
service) and turn the flag off.

0x10 = Non_RSVP flag

The Non_RSVP flag is turned on in the SESSION object of
a PATH Path message whenever the RSVP daemon detects that the
previous RSVP hop included one or more non-RSVP-capable
routers. This flag is forwarded hop-by-hop and passed
to a receiver application. If it is on, it indicates to
the application that even a successful reservation
request may not install the requested QoS at every node
along the path.

0x20 = Maybe_RSVP flag

The Maybe_RSVP flag is turned on in the SESSION object
of a PATH Path message whenever the RSVP daemon is unable to
ascertain whether or not the previous hop included one
or more non-RSVP-capable routers. This flag is
forwarded hop-by-hop and passed to a receiver
application. If it is on and the Non_RSVP flag is off,
the application cannot tell whether or not a successful
reservation request may not install the requested QoS at
every node along the path.

DstPort

The UDP/TCP destination port for the session. Zero may be
used to indicate `none'.

Other SESSION C-Types could be defined in the future to
support other demultiplexing conventions in the transport-
layer or application layer.

Braden, Zhang, et al. Expiration: August 1996 [Page 91] 93]

Internet Draft RSVP Specification February 1996

A.2 RSVP_HOP Class

RSVP_HOP class = 3.

o IPv4 RSVP_HOP object: Class = 3, C-Type = 1

+-------------+-------------+-------------+-------------+
| IPv4 Next/Previous Hop Address |
+-------------+-------------+-------------+-------------+
| Logical Interface Handle |
+-------------+-------------+-------------+-------------+

o IP6 RSVP_HOP object: Class = 3, C-Type = 2

+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 Next/Previous Hop Address +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| Logical Interface Handle |
+-------------+-------------+-------------+-------------+

This object provides the IP address of the interface through which
the last RSVP-knowledgeable hop forwarded this message. The
Logical Interface Handle is a 32-bit number which may be used to
distinguish logical outgoing interfaces as described in Section
3.2; it should be identically zero if there is no logical
interface handle.

Braden, Zhang, et al. Expiration: August 1996 [Page 92] 94]

Internet Draft RSVP Specification February 1996

A.3 INTEGRITY Class

INTEGRITY class = 4.

See [Baker96].

A.4 TIME_VALUES Class

TIME_VALUES class = 5.

o TIME_VALUES Object: Class = 5, C-Type = 1

+-------------+-------------+-------------+-------------+
| Refresh Period R |
+-------------+-------------+-------------+-------------+

Refresh Period

The refresh timeout period R used to generate this message;
in milliseconds.

Braden, Zhang, et al. Expiration: August 1996 [Page 93] 95]

Internet Draft RSVP Specification February 1996

A.5 ERROR_SPEC Class

ERROR_SPEC class = 6.

o IPv4 ERROR_SPEC object: Class = 6, C-Type = 1

+-------------+-------------+-------------+-------------+
| IP4 Error Node Address (4 bytes) |
+-------------+-------------+-------------+-------------+
| Flags | Error Code | Error Value |
+-------------+-------------+-------------+-------------+

o IP6 ERROR_SPEC object: Class = 6, C-Type = 2

+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 Error Node Address (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| Flags | Error Code | Error Value |
+-------------+-------------+-------------+-------------+

Error Node Address

The IP address of the node in which the error was detected.

Flags

0x01 = InPlace

This flag is used only for an ERROR_SPEC object in a
RERR
ResvErr message. If it on, this flag indicates that
there was, and still is, a reservation in place at the
failure point.

0x02 = NotGuilty

This flag is used only for an ERROR_SPEC object in a
RERR
ResvErr message, and it is only set in the interface to the

Braden, Zhang, et al. Expiration: August 1996 [Page 94] 96]

Internet Draft RSVP Specification February 1996

the receiver application. If it on, this flag indicates
that the FLOWSPEC that failed was strictly greater than
the FLOWSPEC requested by this receiver.

Error Code

A one-octet error description.

Error Value

A two-octet field containing additional information about the
error. Its contents depend upon the Error Type.

The values for Error Code and Error Value are defined in Appendix
B.

Braden, Zhang, et al. Expiration: August 1996 [Page 95] 97]

Internet Draft RSVP Specification February 1996

A.6 SCOPE Class

SCOPE class = 7.

This object contains a list of IP addresses, used for routing
messages with wildcard scope without loops. The addresses must be
listed in ascending numerical order.

o IPv4 SCOPE List object: Class = 7, C-Type = 1

+-------------+-------------+-------------+-------------+
| IP4 Src Address (4 bytes) |
+-------------+-------------+-------------+-------------+
// //
+-------------+-------------+-------------+-------------+
| IP4 Src Address (4 bytes) |
+-------------+-------------+-------------+-------------+

o IP6 SCOPE list object: Class = 7, C-Type = 2

+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 Src Address (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
// //
+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 Src Address (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+

Braden, Zhang, et al. Expiration: August 1996 [Page 96] 98]

Internet Draft RSVP Specification February 1996

A.7 STYLE Class

STYLE class = 8.

o STYLE object: Class = 8, C-Type = 1

+-------------+-------------+-------------+-------------+
| Flags | Option Vector |
+-------------+-------------+-------------+-------------+

Flags: 8 bits

(None assigned yet)

Option Vector: 24 bits

A set of bit fields giving values for the reservation
options. If new options are added in the future,
corresponding fields in the option vector will be assigned
from the least-significant end. If a node does not recognize
a style ID, it may interpret as much of the option vector as
it can, ignoring new fields that may have been defined.

The option vector bits are assigned (from the left) as
follows:

19 bits: Reserved

2 bits: Sharing control

00b: Reserved

01b: Distinct reservations

10b: Shared reservations

11b: Reserved

3 bits: Sender selection control

000b: Reserved

001b: Wildcard

010b: Explicit

Braden, Zhang, et al. Expiration: August 1996 [Page 97] 99]

Internet Draft RSVP Specification February 1996

011b - 111b: Reserved

The low order bits of the option vector are determined by the
style, as follows:

WF 10001b
FF 01010b
SE 10010b

Braden, Zhang, et al. Expiration: August 1996 [Page 98] 100]

Internet Draft RSVP Specification February 1996

A.8 FLOWSPEC Class

FLOWSPEC class = 9.

o Class = 9, C-Type = 2: int-serv flowspec

The contents of this object will be specified in documents
prepared by the int-serv working group.

Braden, Zhang, et al. Expiration: August 1996 [Page 99] 101]

Internet Draft RSVP Specification February 1996

A.9 FILTER_SPEC Class

FILTER_SPEC class = 10.

o IPv4 FILTER_SPEC object: Class = 10, C-Type = 1

+-------------+-------------+-------------+-------------+
| IPv4 SrcAddress (4 bytes) |
+-------------+-------------+-------------+-------------+
| ////// | ////// | SrcPort |
+-------------+-------------+-------------+-------------+

o IP6 FILTER_SPEC object: Class = 10, C-Type = 2

+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 SrcAddress (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| ////// | ////// | SrcPort |
+-------------+-------------+-------------+-------------+

o IP6 Flow-label FILTER_SPEC object: Class = 10, C-Type = 3

+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 SrcAddress (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| /////// | Flow Label (24 bits) |
+-------------+-------------+-------------+-------------+

SrcAddress

The IP source address for a sender host. Must be non-zero.

Braden, Zhang, et al. Expiration: August 1996 [Page 100] 102]

Internet Draft RSVP Specification February 1996

SrcPort

The UDP/TCP source port for a sender, or zero to indicate
`none'.

Flow Label

A 24-bit Flow Label, defined in IP6. This value may be used
by the packet classifier to efficiently identify the packets
belonging to a particular (sender->destination) data flow.

Braden, Zhang, et al. Expiration: August 1996 [Page 101] 103]

Internet Draft RSVP Specification February 1996

A.10 SENDER_TEMPLATE Class

SENDER_TEMPLATE class = 11.

o IPv4/UDP SENDER_TEMPLATE object: Class = 11, C-Type = 1

Definition same as IPv4/UDP FILTER_SPEC object.

o IP6/UDP SENDER_TEMPLATE object: Class = 11, C-Type = 2

Definition same as IP6/UDP FILTER_SPEC object.

A.11 SENDER_TSPEC Class

SENDER_TSPEC class = 12.

o Intserv SENDER_TSPEC object: Class = 12, C-Type = 1

The contents of this object are specified in service
specification documents prepared by the int-serv working
group.

Braden, Zhang, et al. Expiration: August 1996 [Page 102] 104]

Internet Draft RSVP Specification February 1996

A.12 ADSPEC Class

ADSPEC class = 13.

o Intserv ADSPEC object: Class = 13, C-Type = 2

The contents of this object are specified in service
specification documents prepared by the int-serv working
group.

Braden, Zhang, et al. Expiration: August 1996 [Page 103] 105]

Internet Draft RSVP Specification February 1996

A.13 POLICY_DATA Class

POLICY_DATA class = 14.

o Type 1 POLICY_DATA object: Class = 14, C-Type = 1

The contents of this object are for further study.

Braden, Zhang, et al. Expiration: August 1996 [Page 104] 106]

Internet Draft RSVP Specification February 1996

A.14 RESV_CONFIRM Resv_CONFIRM Class

RESV_CONFIRM class = 15.

o IPv4 RESV_CONFIRM object: Class = 15, C-Type = 1

+-------------+-------------+-------------+-------------+
| IPv4 Receiver Address (4 bytes) |
+-------------+-------------+-------------+-------------+

o IP6 RESV_CONFIRM object: Class = 15, C-Type = 2

+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IP6 Receiver Address (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+

Braden, Zhang, et al. Expiration: August 1996 [Page 105] 107]

Internet Draft RSVP Specification February 1996

APPENDIX B. Error Codes and Values

The following Error Codes may appear in ERROR_SPEC objects and be
passed to end systems. Except where noted, these Error Codes may
appear only in RERR ResvErr messages.

o Error Code = 00: Confirmation

This code is reserved for use in the ERROR_SPEC object of a RACK
ResvConf message. The Error Value will also be zero.

o Error Code = 01: Admission Control failure

Reservation request was rejected by Admission Control due to
unavailable resources.

For this Error Code, the 16 bits of the Error Value field are:

ssur cccc cccc cccc

where the bits are:

ss = 00: Low order 12 bits contain a globally-defined sub-code
(values listed below).

ss = 10: Low order 12 bits contain a organization-specific sub-
code. RSVP is not expected to be able to interpret this
except as a numeric value.

ss = 11: Low order 12 bits contain a service-specific sub-code.
RSVP is not expected to be able to interpret this except as
a numeric value.

Since the traffic control mechanism might substitute a
different service, this encoding may include some
representation of the service in use.

u = 0: RSVP rejects the message without updating local
state.

u = 1: RSVP may use message to update local state and forward
the message. This means that the message is informational.

Braden, Zhang, et al. Expiration: August 1996 [Page 106] 108]

Internet Draft RSVP Specification February 1996

r: Reserved bit, should be zero.

cccc cccc cccc: 12 bit code.

The following globally-defined sub-codes may appear in the low-
order 12 bits when ssur = 0000:

- Sub-code = 1: Delay bound cannot be met

- Sub-code = 2: Requested bandwidth unavailable

o Error Code = 02: Policy Control failure

Reservation has been rejected for administrative reasons, for
example, required credentials not submitted, insufficient quota
or balance, or administrative preemption. This Error Code may
appear in a PERR PathErr or RERR ResvErr message.

Contents of the Error Value field are to be determined in the
future.

o Error Code = 03: No path information for this Resv message.

No path state for this session. RESV Resv message cannot be
forwarded.

o Error Code = 04: No sender information for this Resv message.

There is path state for this session, but it does not include
the sender matching some flow descriptor contained in the RESV Resv
message. RESV message cannot be forwarded.

o Error Code = 05: Conflicting reservation style

Reservation style conflicts with style(s) of existing
reservation state. The Error Value field contains the low-order
16 bits of the Option Vector of the existing style with which
the conflict occurred. This RESV Resv message cannot be forwarded.

o Error Code = 06: Unknown reservation style

Reservation style is unknown. This RESV Resv message cannot be
forwarded.

o Error Code = 07: Conflicting dest port

Sessions for same destination address and protocol have appeared

Braden, Zhang, et al. Expiration: August 1996 [Page 107] 109]

Internet Draft RSVP Specification February 1996

with both zero and non-zero dest port fields. This Error Code
may appear in a PERR PathErr or RERR ResvErr message.

o Error Code = 08: Ambiguous path

Sender port appears both zero and non-zero in same session in a
PATH
Path message. This Error Code may appear only in a PERR PathErr
message.

o Error Code = 09, 10, 11: (reserved)

o Error Code = 12: Service preempted

The service request defined by the STYLE object and the flow
descriptor has been administratively preempted.

For this Error Code, the 16 bits of the Error Value field are:

ssur cccc cccc cccc

Here the high-order bits ssur are as defined under Error Code
01. The following globally-defined sub-codes may appear in the
low-order 12 bits when ssur = 0000 are to be defined in the
future.

o Error Code = 13: Unknown object class

Error Value contains 16-bit value composed of (Class-Num, C-
Type) of unknown object. This error should be sent only if RSVP
is going to reject the message, as determined by the high-order
bits of the Class-Num. This Error Code may appear in a PERR PathErr
or
RERR ResvErr message.

o Error Code = 14: Unknown object C-Type

Error Value contains 16-bit value composed of (Class-Num, C-
Type) of object.

o Error Code = 15-19: (reserved)

o Error Code = 20: Reserved for API

Error Value field contains an API error code, for an API error
that was detected asynchronously and must be reported via an
upcall.

o Error Code = 21: Traffic Control Error

Braden, Zhang, et al. Expiration: August 1996 [Page 108] 110]

Internet Draft RSVP Specification February 1996

Reservation request was rejected by Traffic Control due to the
format or contents of the request. This RESV Resv message cannot be
forwarded, and continued attempts would be futile.

For this Error Code, the 16 bits of the Error Value field are:

ss00 cccc cccc cccc

Here the high-order bits ss are as defined under Error Code 01.

The following globally-defined sub-codes may appear in the low
order 12 bits (cccc cccc cccc) when ssr = 000:

- Sub-code = 01: Service conflict

Trying to merge two incompatible service requests.

- Sub-code = 02: Service unsupported

Traffic control can provide neither the requested service
nor an acceptable replacement.

- Sub-code = 03: Bad Flowspec value

Mal-formed or unreasonable request.

- Sub-code = 04: Bad Tspec value

Mal-formed or unreasonable request.

o Error Code = 22: Traffic Control System error

A system error was detected and reported by the traffic control
modules. The Error Value will contain a system-specific value
giving more information about the error. RSVP is not expected
to be able to interpret this value.

o Error Code = 23: RSVP System error

The Error Value field will provide implementation-dependent
information on the error. RSVP is not expected to be able to
interpret this value.

In general, every RSVP message is rebuilt at each hop, and the node
that creates an RSVP message is responsible for its correct
construction. Similarly, each node is required to verify the correct
construction of each RSVP message it receives. Should a programming

Braden, Zhang, et al. Expiration: August 1996 [Page 109] 111]

Internet Draft RSVP Specification February 1996

error allow an RSVP to create a malformed message, the error is not
generally reported to end systems in an ERROR_SPEC object; instead,
the error is simply logged locally, and perhaps reported through
network management mechanisms.

The only message formatting errors that are reported to end systems
are those that may reflect version mismatches, and which the end
system might be able to circumvent, e.g., by falling back to a
previous CType for an object; see code 12 and 13 above.

The choice of message formatting errors that an RSVP may detect and
log locally is implementation-specific, but it will typically include
the following:

o Wrong-length message: RSVP Length field does not match message
length.

o Unknown or unsupported RSVP version.

o Bad RSVP checksum

o Illegal RSVP message Type

o Illegal object length: not a multiple of 4, or less than 4.

o Next hop/Previous hop address in HOP object is illegal.

o Conflicting source port: Source port is non-zero in a filter
spec or sender template for a session with destination port
zero.

o Required object class (specify) missing

o Illegal object class (specify) in this message type.

o Violation of required object order

o Flow descriptor count wrong for style

o Logical Interface Handle invalid

o Unknown object Class-Num.

Braden, Zhang, et al. Expiration: August 1996 [Page 110] 112]

Internet Draft RSVP Specification February 1996

APPENDIX C. UDP Encapsulation

An RSVP implementation will generally require the ability to perform
"raw" network I/O, i.e., to send and receive IP datagrams using
protocol 46. However, some important classes of host systems may not
support raw network I/O. To use RSVP, such hosts must encapsulate
RSVP messages in UDP.

The basic UDP encapsulation scheme makes two assumptions:

1. All hosts are capable of sending and receiving multicast packets
if multicast destinations are to be supported.

2. The first/last-hop routers are RSVP-capable.

A method of relaxing the second assumption is given later.

Let Hu be a "UDP-only" host that requires UDP encapsulation, and Hr a
host that can do raw network I/O. The UDP encapsulation scheme must
allow RSVP interoperation among an arbitrary topology of Hr hosts, Hu
hosts, and routers.

RESV, RERR, RTEAR,

Resv, ResvErr, ResvTear, and PERR PathErr messages are sent to unicast
addresses learned from the path or reservation state in the node. If
the node keeps track of which previous hops and which interfaces need
UDP encapsulation, these messages can be sent using UDP encapsulation
when necessary. On the other hand, PATH Path and PTEAR PathTear messages are
send to thedestination address for the session, which may be unicast
or multicast.

The tables in Figures 13 and 14 show the basic rules for UDP
encapsulation of PATH Path and PTEAR PathTear messages, for unicast DestAddress
and multicast DestAddress, respectively. Under the `Send' column,
the notation is `mode(destaddr, destport)'; destport is omitted for
raw packets. The `Receive' column shows the group that is joined
and, where relevant, the UDP Listen port.

It is useful to define two flavors of UDP encapsulation, one to be
sent by Hu and the other to be sent by Hr and R, to avoid double
processing by the recipient. In practice, these two flavors are
distinguished by differing UDP port numbers Pu and Pu'.

The following symbols are used in the tables.

o D is the DestAddress for the particular session.

o G* is a well-known group address of the form 224.0.0.x, i.e., a
group that is limited to the local connected network. [TO BE

Braden, Zhang, et al. Expiration: August 1996 [Page 111] 113]

Internet Draft RSVP Specification February 1996

DEFINED]

o Pu and Pu' are two well-known UDP ports for UDP encapsulation of
RSVP. [TO BE DEFINED]

o Ra is the IP address of the router interface `a'.

o Tr is the TTL value of the specific PATH Path message.

o Router interface `a' is on the local network connected to Hu and
Hr.

o [RA] indicates that the Router Alert option is sent.

UNICAST DESTINATION D:

RSVP RSVP
Node Send Receive
___ _____________ _______________
Hu UDP(D/Ra,Pu) UDP(D,Pu)
[Note 1] and UDP(D,Pu')
[Note 2]

Hr Raw(D,Tr)[RA] Raw()
and if (UDP) and UDP(D, Pu)
then UDP(D,Pu') [Note 2]
(Ignore Pu')

R (Interface a):
Raw(D,Tr)[RA] Raw()
and if (UDP) and UDP(Ra, Pu)
then UDP(D,Pu') (Ignore Pu')

Figure 13: UDP Unicast Encapsulation Rules for Path Messages

Braden, Zhang, et al. Expiration: August 1996 [Page 112] 114]

Internet Draft RSVP Specification February 1996

MULTICAST DESTINATION D:

RSVP RSVP
Node Send Receive
___ _____________ _________________
Hu UDP(G*,Pu) UDP(D,Pu')
[Note 3]
and UDP(G*,Pu)

Hr Raw(D,Tr)[RA] Raw()
and if (UDP) and UDP(G*,Pu)
then UDP(D,Pu') (Ignore Pu')

R (Interface a):
Raw(D,Tr)[RA] Raw()
and if (UDP) and UDP(G*,Pu)
then UDP(D,Pu') (Ignore Pu')

Figure 14: UDP Multicast Encapsulation Rules for Path Messages

[Note 1] Hu sends a unicast PATH Path message either to the destination
address D, if D is local, or to the address Ra of the first-hop
router. Ra is presumably known to the host.

[Note 2] Here D is the address of the local interface through which
the message arrived.

[Note 3] This assumes that the application has joined the group D.

A router may determine if its interface X needs UDP encapsulation by
listening for UDP-encapsulated PATH Path messages that were sent to either
G* (multicast D) or to the address of interface X (unicast D). There
is one failure mode for this scheme: if no host on the connected
network acts as an RSVP sender, there will be no PATH Path messages to
trigger UDP encapsulation. In this (unlikely) case, it will be
necessary to explicitly configure UDP encapsulation on the local
network interface of the router.

When a UDP-encapsulated packet is received, the IP TTL is not
available to the application on most systems. The RSVP daemon that
receives a UDP-encapsulated PATH Path or PTEAR PathTear message should therefore
use the Send_TTL field of the RSVP common header as the effective
receive TTL. This may be overridden by manual configuration.

Braden, Zhang, et al. Expiration: August 1996 [Page 113] 115]

Internet Draft RSVP Specification February 1996

We have assumed that the first-hop RSVP-capable router R is on the
directly-connected network. There are several possible approaches if
this is not the case.

1. Hu can send both unicast and multicast sessions to UDP(Ra,Pu)
with TTL=Ta

Here Ta must be the TTL to exactly reach R. If Ta is too small,
the PATH Path message will not reach R. If Ta is too large,
multicast routing in R will forward the UDP packet into the
Internet until its hop count expires. This will turn on UDP
encapsulation between routers within the Internet, perhaps
causing bogus UDP traffic. The host Hu must be explicitly
configured with Ra and Ta.

2. A particular host on the LAN connected to Hu could be designated
as an "RSVP relay host". A relay host would listen on (G*,Pu)
and forward any PATH Path messages directly to R, although it would
not be in the data path. The relay host would have to be
configured with Ra and Ta.

References

[Baker96] Baker, Fred, "RSVP Cryptographic Authentication", Internet
Draft draft-ietf-rsvp-md5-01.txt, February 1996.

[ISInt93] Braden, R., Clark, D., and S. Shenker, "Integrated Services
in the Internet Architecture: an Overview", RFC 1633, ISI, MIT, and
PARC, June 1994.

[CSZ92] Clark, D., Shenker, S., and L. Zhang, "Supporting Real-Time
Applications in an Integrated Services Packet Network: Architecture
and Mechanisms", Proc. SIGCOMM '92, Baltimore, MD, August 1992.

[FJ94] Floyd, S. and V. Jacobson, "Synchronization of Periodic Routing
Messages", IEEE/ACM Transactions on Networking, Vol. 2, No. 2,
April, 1994.

[Katz95] Katz, D., "IP Router Alert Option", Internet Draft draft-
katz-router-alert-01.txt, Cisco Systems, November 16, 1995.

[Partridge92] Partridge, C., "A Proposed Flow Specification", RFC 1363,
BBN, September 1992.

[IServ93] Shenker, S., Clark, D., and L. Zhang, "A Service Model for an
Integrated Services Internet", Work in Progress, October 1993.

Braden, Zhang, et al. Expiration: August 1996 [Page 114] 116]

Internet Draft RSVP Specification February 1996

[RSVP93] Zhang, L., Deering, S., Estrin, D., Shenker, S., and D.
Zappala, "RSVP: A New Resource ReSerVation Protocol", IEEE Network,
September 1993.

[ServTempl95a] Shenker, S., "Network Element Service Specification
Template", Internet Draft draft-ietf-intserv-svc-template-00.txt,
Integrated Services Working Group, March 1995.

[Shenker94] Shenker, S., "Two-Pass or Not Two-Pass", Current Meeting
Report, RSVP Working Group, Proceedings of the Thirtieth Internet
Engineering Task Force, Toronto, Canada, July 1994.

Security Considerations

See Section 2.8.

Authors' Addresses

Lixia Zhang
Xerox Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304

Phone: (415) 812-4415
EMail: Lixia@PARC.XEROX.COM

Bob Braden
USC Information Sciences Institute
4676 Admiralty Way
Marina del Rey, CA 90292

Phone: (310) 822-1511
EMail: Braden@ISI.EDU

Steve Berson
USC Information Sciences Institute
4676 Admiralty Way
Marina del Rey, CA 90292

Phone: (310) 822-1511
EMail: Berson@ISI.EDU

Braden, Zhang, et al. Expiration: August 1996 [Page 115] 117]

Internet Draft RSVP Specification February 1996

Shai Herzog
USC Information Sciences Institute
4676 Admiralty Way
Marina del Rey, CA 90292
Palo Alto, CA 94304

Phone: (310) 822 1511
EMail: Herzog@ISI.EDU

Sugih Jamin
Computer Science Department
University of Southern California
Los Angeles, CA 90089-0871

Phone: (213) 740-6578
EMail: jamin@catarina.usc.edu

Braden, Zhang, et al. Expiration: August 1996 [Page 116] 118]

----