Internet DRAFT - draft-aboulmagd-ccamp-crldp
draft-aboulmagd-ccamp-crldp
CCAMP WG O. Aboul-Magd
Document: draft-aboulmagd-ccamp-crldp-00.txt Nortel Networks
Feb. 2002
Supporting Call and Connection Control Separation using CR-LDP
Status of this Memo
This document is an Internet-Draft and is in full conformance wit
all provisions of Section 10 of RFC2026 [1].
Internet-Drafts are working documents of the Internet Engineering
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1. Abstract
There has been a recent activity towards the use of GMPLS-based
protocols (CR-LDP and RSVP-TE) for automatic switched optical
networks (ASON) at the ITU-T. ASON control plane requirements
mandates the separate treatment of call and connection control. This
draft proposes additional CR-LDP messages necessary for satisfying
this goal.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC-2119 [2].
3. Introduction
Automatic Switched optical networks (ASON) architecture [3] and
GMPLS are progressing in parallel at the ITU-T and IETF
respectively. As it has been pointed out in [4], the two efforts are
complementary in the sense that GMPLS-based protocol could be used
for the realization of ASON control plane. Recently GMPLS-based
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protocols have been submitted to ITU-T [5,6] as possible candidates
for ASON signaling implementation as defined in G.7713 [7].
One important architecture principle of ASON is that call and
connection control are treated separately. With this separation
there could be the case where a single call has one or more
connections associated to it. It is also quite possible to have a
call with no connections associated to it, for example during
recovery times.
The current set of GMPLS signaling protocols, i.e. CR-LDP and RSVP-
TE do not support this requirement. In reality the notion of a call
is absent in both protocols. A label switched path (LSP), or a
connection, is set end-to-end by assigning a set of labels on the
different nodes along the path. Once an LSP is deleted, all the
information regarding its end points is lost.
This draft describes messages necessary to introduce call and
connection control separation to CR-LDP.
4. CR-LDP Call Control
As it has been stated in [8], (CR-)LDP employs four categories of
messages. Those categories are:
1. Discovery messages, use to announce and maintain the presence of
a network element in the network
2. Session messages, used to establish, maintain, and terminate LDP
sessions between LDP pairs
3. Advertisement messages, used to create, change, and delete label
mappings
4. Notification messages, used to provide advisory information to
signal error information.
A new category related to query messages was introduced in [9] and
is used to query different information related to an operational LSP
(connection).
The third category of the above list is the one that is supposed to
be used for connection creation, deletion, and modification in an
optical network. New connection is created by assigning a
generalized ingress and egress labels at every node along the path
of the connection. This process is achieved using Label Request and
Label Mapping messages, which carry in their TLVs the necessary
characteristics of the required connection. Label Request and Label
Mapping requests and confirm the assignment of a generalized label
to a connection. In a similar way Label Withdraw and Label Release
Messages are used to delete a connection by releasing the label
assigned to it.
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The processes described here are all at the connection level since
they all involve request, assignment, or release of a label. In
contrast to that, with the separation of call and connection in
mind, the setup of a call MUST not involve any of those processes. A
call setup is mainly for the exchange of call control information
between the two end points of a call. Thus there is the need for the
introduction of a new category specifically for call control. The
new category is called here "call control messages".
4.1 CR-LDP Call Control Messages
This section describes those additional messages that are needed to
support the separation of call and connection control requirements
in ASON.
A mechanism for call setup and deletion is needed for CR-LDP to
support call control that is separate from that of the connection
control part described previously. This mechanism necessitates the
introduction of two CR-LDP messages, Call Setup and Call Delete
messages.
The calling party sends the Call Setup message and it carries
information related to the calling and called parties, e.g. their
addresses, etc. It may also carry information related to the service
level agreement (SLA) associated to a particular call.
The Call Delete message could be initiated by any network entity
(network or client) to terminate a call. All connections associated
with this call have to be cleared before clearing the call.
The formats and procedures for Call Setup and Call Delete are given
in section 5.
4.2 Impact on Other (CR-)LDP Messages
The introduction of call control messages is expected to have some
impact on other (CR-)LDP messages in two ways. The first impact is
related to new TLV added to some of the messages. For instance, with
the call and connection control separation, it is necessary to
introduce a call association indication to the Label Request message
to indicate the call for which the requested connection is
associated. The impact on LDP messages are described in section 6.
5. Call Setup and Call Delete Messages
This section describes the encoding of the two messages related to
CR-LDP call control.
5.1 Call Setup Message
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The format of the Call Setup message is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Call Setup (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Calling Party Number TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Called Party Number TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Call ID TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Message ID:
32-bit value used to identify this message
Calling Party Number TLV:
The address of the party that is initiating the call request. It
has the same format as the Transport Network Assigned (TNA)
address in [10]
Called Party Number TLV:
The address of the called party. It has the same format as the
TNA in [10]
Call ID TLV:
The purpose of the call identifier (Call ID) TLV is to locally
identify a call in the context of separated call and connection
control environment.
The format of the Call Identifier TLV is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Call ID (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Call ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Procedure:
The Calling party initiates a call setup by sending the Call
Setup message. The Call Setup message SHALL contain all the
information required by the network to process the call. In
Particular the calling and called party addresses.
The Call Setup message MUST include call identifier TLV. The call
control entity shall identify the call using the selected
identifier for the lifetime of the call.
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The Call Setup message shall progress through the network to the
called party. The called party may accept or reject the incoming
call. An LDP Notification message with the appropriate status code
(to be defined) shall be used to inform the calling party whether
the setup is successful. The call can be rejected by either the
network, e.g. for policy reasons, or by the called party.
5.2 Call Delete Message
The format of the Call Setup message is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Call Delete (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Calling Party Number TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Called Party Number TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Call ID TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Message ID:
32-bit value used to identify this message
Calling Party Number TLV:
Same as for Call Setup Message
Called Party Number TLV:
Same as for Call Setup message
Call ID TLV:
Same as for Call Setup message
Procedure:
The Call Delete message is sent by any entity of the network to
indicate the desire to terminate an already established call. The
Call Setup message SHALL contain all the information required by
the network to process the call. In Particular the calling and
called party addresses. Confirmation of call deletion is indicated
to the request initiator using a Notification message with the
appropriate status code.
6. Impact on Other LDP Messages
The separation of call and connection control allows one or more
connection to be associated to the same call. This will have an
impact on existing LDP messages relevant to the establishment and
deletion of a connection (LSP). The full impact on LDP messages in
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terms of additional TLVs and procedures will be addressed in future
revisions pf the draft.
7. Security Considerations
This draft doesn't introduce any new security issues other than
those defined in RFC 3036 and RFC 3212
8. References
1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
2 Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
3 M. Mayer, Ed., "Architecture for Automatic Switched Optical
Networks (ASON)", ITU G.8080/Y1304, V1.0, October 2001
4 O. Aboul-Magd, et. al., "Automatic Switched Optical Networks
(ASON) Architecture and its Related Protocols", draft-ietf-ipo-
ason-02.txt, work in progress, Feb. 2002.
5 S. Shew, "A Proposal for DCM Signaling Using GMPLS CR-LDP", ITU
Contribution, WD25, Feb. 2002.
6 D. Pendarakis, "Proposal for G.7713.2 Based on GMPLS", ITU
Contribution, WD06, Feb. 2002
7 Z. Lin, Ed., "Distributed Call and Connection Management", ITU
G.7713/Y.1704, October 2001
8 Anderson, L., et. al., "LDP Specification", RFC 3036, January
2001
9 P. Ashwood-Smith, et. al., "MPLS LDP Query Message Description",
draft-ietf-mpls-lsp-query-txt.03, work in progress, August 2001.
10 Rajagopalan, B. Editor, "User Network Interface (UNI) 1.0
Signaling Specifications", OIF Contribution, OIF2000.125.7,
October 2001
9. Author's Addresses
Osama Aboul-Magd
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Nortel Networks
P.O. Box 3511, Station "C"
Ottawa, Ontario, Canada
K1Y - 4H7
Phone: 613-763-5827
Email: osama@nortelnetworks.com
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Aboul-Magd Expires August 2002 8
