WDIFF

draft-ietf-v6ops-unman-scenarios-00.txt --> draft-ietf-v6ops-unman-scenarios-01.txt

<draft-ietf-v6ops-unman-scenarios-00.txt>
<draft-ietf-v6ops-unman-scenarios-01.txt> Microsoft
January 10,
June 3, 2003 R. Austein
Expires July 10, December 3, 2003 Bourgeois Dilettant
S. Satapati
Cisco Systems, Inc.
R. van der Pol
NLnet Labs

Unmanaged Networks IPv6 Transition Scenarios

Status of this memo

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.

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."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

Abstract

In order to evaluate the suitability of IPv6 transition mechanisms,
we need to define the scenarios in which these mechanisms have to be
used. One specific scope is the "unmanaged networks", network", which typically correspond
corresponds to a home networks or small office networks. network. The scenarios are
specific to single link subnet, and are defined in terms of IP
connectivity supported by the home gateway and the ISP. We first
examine the generic requirements of four classes of applications:
local, client, peer to peer and server. Then, for each scenario, we
infer transition requirements by analyzing the needs for smooth
migration of applications from IPv4 to IPv6.

1 Introduction

In order to evaluate the suitability of transition mechanisms, we
need to define the environment or scope in which these mechanisms
have to be used. One specific scope is the "unmanaged networks",
which typically correspond to home networks or small office
networks.

This document studies the requirement posed by various transition

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scenarios, and is organized in four main sections. Section 2 defines
the topology that we are considering. Section 3 presents the four
classes of applications that we consider for unmanaged networks:
local applications, client applications, peer-to-peer applications,
and server applications. Section 4 studies the requirements of these
four classes of applications. Section 5 analyses how these
requirements translate into four configurations which we expect to
encounter during IPv6 deployment: gateways which do not provide
IPv6, dual-stack gateways connected to dual-stack ISPs, dual-stack
gateways connected to IPv4-only ISPs, and IPv6-capable gateways
connected to IPv6-only ISPs. While these four configurations are
certainly not an exhaustive list of possible configurations, we
believe that they represent the common cases for unmanaged networks.

2 Topology

The typical unmanaged network is composed of a single subnet,
connected to the Internet through a single Internet Service Provider
(ISP)connection.
(ISP) connection. Several hosts are may be connected to the subnet:

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+------+
| Host +--+
+------+ |
|
+------+ |
| Host +--+ +--------------
+------+ | |
: +-----+
: +---------+ | |
+--+ Gateway +------| ISP | Internet
: +---------+ | |
: +-----+
+------+ | |
| Host +--+ +--------------
+------+ |
|
+------+ |
| Host +--+
+------+

Between the subnet and the ISP access link is a gateway, which may
or may not perform NAT and firewall function. A key point of this
configuration is that the gateway is typically not "managed". In
most cases, it is a simple "appliance", which incorporates some
static policies. There However, there are however many cases in which the gateway
is procured and configured by the ISP, and there are also some
common cases in which we find two gateways back to back gateways, back, one managed
by the ISP and the other added by the owner of the unmanaged
network.

The access link between the unmanaged network and the ISP can might be
either static, i.e. a static, permanent connection, connection or dynamically
established, i.e. a dynamic connection such

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as a dial-up or ISDN connection. line.

In a degenerate case, an unmanaged network can be constituted might consist of a single
host, directly connected to an ISP.

3 Applications

Users may use or wish to use the

Our definition of unmanaged network services in four
types networks explicitly exclude networks
composed of applications: local, client, servers multiple subnets. We will readily admit that some home
networks and peer-to-peers.
These applications may or may not some small business networks contain multiple subnets,
but in the current state of the technology these multiple subnet
networks are not "unmanaged": some competent administrator has to
explicitly configure the routers. We will thus concentrate on single
subnet networks, where no such competent operator is expected.

3 Applications

Users may use or wish to use the unmanaged network services in four
types of applications: local, client, servers and peer-to-peers.
These applications may or may not run easily on today's network:
their status vary. networks
(some do, some don't).

3.1 Local applications

Local applications

"Local applications" are only meant to only involve the hosts that are
part of the unmanaged network. Typical examples are the sharing of would be file
sharing or printers. printer sharing.

Local applications work effectively in IPv4 unmanaged networks, even

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when the gateway performs NAT or firewall function. In fact,
firewall services at the gateway are often deemed desirable, as they
isolate the local applications from interference by Internet users.

3.2 Client applications

Client applications

"Client applications" are those that involve a client on the
unmanaged network and a server at a remote location. A typical example is Typical
examples would be accessing a web server from a client inside the
unmanaged network, or reading and sending e-mail with the help of a
server outside the unmanaged network.

Local

Client applications tend to work correctly in IPv4 unmanaged
networks, even when the gateway performs NAT or firewall function:
these translation and firewall functions are precisely designed precisely to
enable client applications.

3.3 Peer-to-peer applications

There are really two kinds of peer-to-peer applications, the "local peer-
to-peer" that "peer-to-peer" applications: ones
which only involve hosts on the unmanaged network, and the
"remote peer-to-peer" that ones which
involve both one or more hosts on the unmanaged network and one or
more hosts outside the unmanaged network. We will only consider here the "remote peer-to-peer"
latter kind of peer-to-peer applications, as since the local peer-to-peer
applications are former can be
considered a subset of the "local applications." kind of local applications discussed

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in section 3.1.

Peer-to-peer applications are a restricted subset of the server
applications, "server
applications" (discussed in section 3.4), in which the services are
only meant to be used by
well identified well-identified peers outside the unmanaged
network. These applications are often facilitated by a server
outside the unmanaged networks. Examples of a peer-to-peer application
applications would be a video-
conference video-conference over IP, facilitated by a SIP
Session Invitation Protocol (SIP) server, or a distributed game
application, facilitated by a "game lobby".

Peer-to-peer applications often don't work well in unmanaged IPv4
networks. Application developers often have to enlist the help of a
"relay server", to effectively restructure in effect restructuring the peer-to-peer connection in two
into a pair of back-to-back client/server connections.

3.4 Server applications

Server applications

"Server applications" involve running a server in the unmanaged
network,
network for use by other parties outside the network. Examples Typical
examples would be running a web server or an e-mail server on one of
the hosts inside the unmanaged network.

Deploying these servers in most unmanaged IPv4 networks requires
some special programming of the NAT or firewall, and is more complex
when the NAT only publishes a small number of global IP addresses
and relies on "port translation". In the common case in which the
NAT manages exactly one global IP address and relies on "port
translation", a given external port can only be used by one internal

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server.

Deploying servers usually requires providing the servers each server with a
stable DNS name, and associating the a global IPv4 address with that
name, whether the address be that of the
nat/firewall with server itself or that name. of
the router acting as a firewall or NAT. Since updating DNS is a
management task, it somewhat falls somewhat outside the scope of an unmanaged
network. On the other hand, it is also possible to use out-of-band
techniques, such
techniques (such as cut-and-paste into an instant message system, system) to
pass around the address of the target server.

4 Application requirements of an IPv6 unmanaged network

As we transition to IPv6, we must meet the requirements of the
various applications, which we can summarize in the following way:
the
applications that used to work well with IPv4 should continue
working well during the transition; it should be possible to use
IPv6 to deploy new applications that are currently hard to deploy in
IPv4 networks; and the deployment of these IPv6 applications should
be simple and easy to manage. manage, but the solutions should also be
robust and secure.

The application requirements are expressed in mostly for IPv6 Unmanaged Networks fall into

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three
dimensions: general categories: connectivity, naming, and security.
Connectivity issues include the provision of IPv6 addresses and
their quality: do host hosts need a global scope address, addresses, should this address these
addresses be stable, or stable or, more
precisely precisely, what should be the expected lifetime
lifetimes of the address. these addresses be? Naming issues include the
management of names for the hosts: do hosts need a DNS-name, DNS names, and is
inverse name resolution a requirement. requirement? Security issues include
possible restriction to connectivity, privacy concerns, and concerns and,
generally speaking speaking, the security of the applications.

4.1 Requirements of local applications

Local applications require local connectivity. They must continue
working to
work even if the unmanaged network is isolated from the Internet.

Local applications typically use ad hoc naming systems. Many of
these systems are proprietary; an example of a standard system is
the service location protocol (SLP).

The security of local applications is will usually be enhanced if these
applications can be effectively isolated from the global Internet.

4.2 Requirements of client applications

Client applications require global connectivity. In an IPv6 network,
we would expect the client to use a global IPv6 address, which will
have to remain stable for the duration of the client-server session.

Client applications typically use the domain name system to locate
servers. In an IPv6 network, the client must be able to locate a DNS
server.

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resolver.

Many servers try to look up a DNS name associated to the IP address
of the client. In an IPv4 network, this IP address will often be
allocated by the Internet service provider to the gateway, and the
corresponding PTR record will be maintained by the ISP. In most many
cases, these PTR records are perfunctory, derived in an algorithmic
fashion from the IPv4 address; the main information that they
contain is the domain name of the ISP. Whether or not an equivalent
function should be provided in an IPv6 network is unclear.

4.2.1 Privacy requirement of client applications

We may debate

It is debatable whether the IPv6 networking service should be
engineered to enhance the privacy of the clients, and specifically
whether the support of for RFC 3041 should be required. RFC 3041 enables
hosts to pick IPv6 addresses in which the host identifier is
randomized; this was designed to make sure that the IPv6 addresses
and the host identifier cannot be used to track the Internet
connections of a device's owner.

Many observe that randomizing the host identifier portion of the

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address is only a half measure. If the unmanaged network address
prefix remains constant, the randomization only hides which host in
the unmanaged network originates a given connection, e.g. the
children's computer versus their parents'. This would place the
privacy rating of such connections on a par with that of IPv4
connections originating from an unmanaged network in which a NAT
manages a static IPv4 address; in both case, the IPv4 address or the
IPv6 prefix can be used to identify the unmanaged network, e.g. the
specific home from which the connection originated.

Randomization

However, randomization of the host identifier does however provide benefits.
First, if some of the hosts in the unmanaged network are mobile, the
randomization destroys any correlation between the addresses used at
various locations: the addresses alone could not be used to
determine whether a given connection originates from the same laptop
moving from work to home, or used on the road. Second, the
randomization removes any information that could be extracted from a
hardwired host identifier; for example, it will prevent outsiders to
correlate
from correlating a serial number with a specific brand of expensive
electronic equipment, and to use this information for planning
marketing campaigns or possibly burglary attempts.

Randomization of the addresses is indeed not sufficient to guarantee
privacy. Usage can be tracked by a variety of other means, from
application level "cookies" to complex techniques involving data
mining and traffic analysis. However, just because privacy can be
breached by other means is not a sufficient reason to enable
additional tracking through IPv6 addresses.

Randomization of the host identifier has some cost: the address
management in hosts is more complex for the hosts and the gateway

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may have to maintain a larger cache of neighbor addresses; however,
experience from existing implementation shows that these costs are
not overwhelming. Given the limited benefits, it would be
unreasonable to require that all hosts use privacy addresses;
however, given the limited costs, it is reasonable to require that
all unmanaged network networks allow use of privacy addresses by those hosts
who so choose.
that choose to do so.

4.3 Requirements of peer-to-peer applications

Peer-to-peer applications require global connectivity. In an IPv6
network, we would expect the peers to use a global IPv6 address,
which will have to remain stable for the duration of the peer-to-
peer between client and server. session.

Peer-to-peer applications often use ad hoc naming systems, sometimes
derived from an "instant messaging" service. (Peer-to-peer
applications that rely on the DNS for name resolution have the same
naming requirements as server applications, which are discussed in
the next section.) Many of these systems are proprietary; an example
of a standard system is the session
initiation invitation protocol (SIP). In

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these systems, the peers register their presence to a "rendezvous"
server, using a name specific to the service; the case of SIP, they
would use a SIP URL, of the form "sip:user@example.com". A peer to peer-to-
peer session typically starts by with an exchange of synchronization
messages through the rendezvous servers, during which the peers
exchange the addresses that will be used for the session.

There are multiple aspects to the security of peer-to-peer
applications, many of which relate to the security of the rendezvous
system. If we assume that the peers have been able to safely
exchange their IPv6 addresses, the main security requirement is the
capability to safely exchange data between the peers, without
interference by third parties.

Private conversations by one of the authors with developers of peer-to-peer peer-
to-peer applications
showed suggest that many would be willing to consider
an "IPv6-only" model if they can get two guarantees:

1) That there is no regression from IPv4, i.e. that all customers
that
who could participate in a peer-to-peer application using IPv4 can
also be reached by IPv6.

2) That IPv6 provides a solution for at least some of their hard
problems, i.e. e.g. enabling peers located behind an IPv4 NAT to
participate in a peer-to-peer application.

Requiring IPv6 connectivity for a popular peer-to-peer application
could create what economists refer to as a "network effect", which
in turn could significantly speed up the deployment of IPv6.

4.4 Requirements of server applications

Server applications require global connectivity, which in an IPv6

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network implies global addresses. In an IPv4 network utilizing a
NAT, for each service provided by a server, the NAT has to be
configured to forward packets sent to that service to the server
that offers the service.

Server applications normally rely on the publication of the server's
address in the DNS. This, in turns, turn, requires that the server be
provisioned with a "global DNS name".

The DNS entries for the server will have to be updated, preferably
in real time, if the server's address changes. In practice, updating
the DNS is can be slow, which implies that server applications will
have a better chance of being deployed if the IPv6 addresses remain
stable for a long period.

The security of server applications depends mostly on the
correctness of the server, and also on the absence of collateral
effects: many incidents occur when the opening of a server on the
Internet inadvertently enables remote access to some other services

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on the same host.

5 Stages of IPv6 deployment

The

We expect the deployment of IPv6 over time is expected to proceed from an initial state in
which there is little or no deployment, deployment to a final stage in which we
might retire the IPv4 infrastructure. We expect this process to
stretch over several many years; we also expect it to not be synchronized,
as different parties involved will deploy IPv6 at different pace. paces.
In order to get some clarity, we distinguish three entities involved
in the transition of an unmanaged network: the ISP (possibly
including ISP CPE), consumer premise equipment (CPE)), the home gateway gateway,
and the hosts (computers and appliances). Each can support IPv4-only, IPv4-
only, both IPv4 and IPv6 or IPv6-only. That gives us 27
possibilities. We describe the most important cases. We will consider assume
that in all cases the hosts are a combination of IPv4-only, dual
stack and (perhaps) IPv6-only hosts.

The cases we will consider are:

A) Gateway a gateway which does not provide IPv6 at all;
B) ISP and a dual-stack gateway are connected to a dual stack ISP;
C) Gateway is IPv6 capable, a dual stack, stack gateway connected to an IPV4-only ISP; and
D) a gateway connected to an IPv6-only ISP

In most of these cases we will assume that the gateway includes a
NAT: we realize that this is not
D) ISP always the case, but we submit that
it is IPv6-only

The common enough that we have to deal with it; furthermore, we
believe that the non-NAT variants of these cases map fairly closely
to this same set of cases. For example, the case where in which there is
no NAT and the CPE is a bridge rather than a router maps fairly well
to cases B, C, or D, depending on which protocols the ISP supports;
similarly, the case in which the CPE is IPv6 capable a router but the gateway is not is
similar a NAT
maps either to case B or case C depending on what the CPE router
supports. Last, note that the combination of an IPv6-capable ISP
with a gateway that doesn't support IPv6 is, in effect, equivalent
to case A.

5.1 Case A, host deployment of IPv6 applications

In this case the gateway doesn't provide IPv6; the ISP may or may
not provide IPv6, but this is not relevant, since the non-upgraded
gateway would prevent the hosts from using the ISP service. Some
hosts will try to get IPv6 connectivity, in order to run
applications that require IPv6, or work better with IPv6. The hosts
in this case will have to handle the IPv6 transition mechanisms on
their own.

There are two variations of this case, depending on the type of
service implemented by the gateway. In many cases, the gateway is a
direct obstacle to the deployment of IPv6, but a gateway which is
some form of bridge-mode CPE or which is a plain (neither

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filtering nor NAT) router does not really fall into this category.

5.1.1 Application support in Case A

The focus of Case A is to enable communication between a host on the
unmanaged network and some IPv6-only hosts outside of the network.
The primary focus in the immediate future, i.e. for the early
adopters of IPv6, will be peer-to-peer applications. However, as
IPv6 deployment progresses, we will likely find a situation where
some networks have IPv6-only services deployed, at which point we
would like case A client applications to be able to access those
services.

Local applications are not a primary focus of Case A. At this stage,
we expect all clients in the unmanaged network to have either IPv4
only or dual stack support. Local applications can continue working
using IPv4.

Server applications are also not a primary focus of Case A. Server
applications require DNS support, which is difficult to engineer for
clients located behind a NAT. NAT, which is likely to be present in this
case. Besides, server applications, applications at this
stage, present cater mostly to IPv4
clients; putting up an IPv6-only server is not very attractive.

In contrast, peer-to-peer applications are probably both attractive
and easy to deploy: they are deployed in a coordinated fashion as
part of a peer-to-peer network, which means that hosts can all
receive some form of IPv6 upgrade; they often provide their own
naming infrastructure, in which case they are not dependent on DNS
services.

5.1.2 Addresses and connectivity in Case A

We saw in 5.1.1 that a primary the likely motivation for the deployment of IPv6
connectivity in hosts in case A is participation a desire to use peer-to-peer applications, and also to IPv6-only
client IPv6 applications. These applications require that all
participating nodes get some form of IPv6
connectivity, i.e. at least one globally reachable IPv6 address. IPv6 connectivity, i.e. at
least one globally reachable IPv6 address.

If the local gateway provides global IPv4 addresses to the local
hosts, then these hosts can individually exercise the mechanisms
described in case C, "IPv6 connectivity without provider support."
If the local gateway implements a NAT function, another type of
mechanism is needed. The mechanism to provide connectivity to peers
behind NAT should be easy to deploy, and light weight; it will have
to involve tunneling over a protocol that can easily traverse NAT,
either TCP or preferably UDP, as this is the practical way to traverse a NAT. tunneling over TCP can result in
poor performances in case of time-outs and retransmission. If
servers are needed, these servers will in practice have to be
deployed as part of the "support infrastructure" for the peer-to-peer peer-to-
peer network or for an IPv6 based IPv6-based service; economic reality implies
that the cost of running these servers should be as low as possible.

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5.1.3 Naming services in Case A

At this phase of IPv6 deployment, hosts in the unmanaged domain have
access to DNS services over IPv4, through the existing gateway. DNS
resolvers are supposed to serve AAAA records, even if they only
implement IPv4; the local hosts should thus be able to obtain the
IPv6 addresses of IPv6-only servers.

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Reverse lookup is hard difficult to provide for hosts on the unmanaged
network if the gateway is not upgraded. This is a potential issue
for client applications. Some servers require a reverse lookup as
part of accepting a client's connection, and may require that the
direct lookup of the corresponding name matches the IPv6 address of
the client. There is thus a requirement
to either to provide a reverse
lookup solution, or to make sure that IPv6 servers do not require
reverse lookup.

5.2 Case B, IPv6 connectivity with provider support

In this case the ISP and gateway are both dual stack. The gateway
can use native IPv6 connectivity to the ISP and can use an IPv6
prefix allocated by the ISP.

5.2.1 Application support in Case B

If the ISP and the gateway are dual-stack, client applications,
peer-to-peer applications and server applications can all be enabled
easily on the unmanaged network.

We expect the unmanaged network to include three kinds of hosts:
IPv4 only, IPv6-only, and dual stack. Obviously, dual stack hosts
can interact easily with either IPv4 only hosts or IPv6-only hosts,
but an IPv4 only host and an IPv6-only host cannot communicate
without a third party performing some kind of translation service.
Our analysis concludes that unmanaged networks should not have to
provide such translation services.

The argument for providing translation services is that their
availability would accelerate the deployment of IPv6-only devices,
and thus the transition to IPv6. This is however a dubious argument,
since it can also be argued that the availability of these
translation services will reduce the pressure to provide IPv6 at
all, and to just continue fielding IPv6-only IPv4-only devices. The remaining
pressure to provide IPv6 connectivity would just be the difference
in "quality of service" between a translated exchange and a native
interconnect.

The argument against translation service is the difficulty of
providing these services for all applications, compared to the
relative ease of installing dual stack solutions in an unmanaged
network. Translation services can be provided either by application

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relays such as HTTP proxies, or by network level services such as
NAT-PT. Application relays pose several operational problems: first,
one must develop relays for all applications; second, one must
develop a management infrastructure to provision the host with the
addresses of the relays; in addition, the application may have to be
modified if one wants to use the relay selectively, e.g. only when
direct connection is not available. Network level translation poses
similar problems: in practice, network level actions must be
complemented by "application layer gateways" that will rewrite
references to IP addresses in the protocol, and while these relays tend to

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be
are not necessary for every application; application, they are necessary for
enough applications to make any sort of generalized translation
quite problematic; hosts may need to be parameterized to use the
translation service; and designing the right algorithm to decide
when to translate DNS requests has proven very difficult.

Not assuming translation services in the network appears to be both
more practical and more robust. If the market requirement for a new
device requires that it interacts interact with both IPv4 and IPv6 hosts, we
may expect the manufacturers of these devices to program them with a
dual stack capability; in particular, we expect general purpose
systems such as personal computers to be effectively dual-stack. The
only devices that are expected to be capable of only supporting IPv6
are those who are designed for specific applications, which do not
require interoperation with antique IPv4-only systems. We also observe that
providing both IPv4 and IPv6 connectivity in an unmanaged network is
not particularly difficult; indeed there is difficult: we have a
well established experience fair amount of experience
using IPv4 in these unmanaged networks in parallel with other protocols
such as as, for example example, IPX.

5.2.2 Addresses and connectivity in Case B

In Case B, the upgraded gateway will behave act as an IPv6 router; it will
continue providing the IPv4 connectivity of a non-upgraded connectivity, perhaps using NAT. Nodes
in the local network will typically obtain:

- IPv4 natted addresses, addresses (from or via the gateway),
- IPv6 link local addresses, and
- IPv6 global addresses.

The hosts could also obtain IPv6 site local addresses, if the
gateway advertises a site local prefix. This is as debatable: site
local addresses provide

In some isolation to site local application
from network connectivity events and network based attacks; however,
managing non unique addresses can networks, NAT will not be problematic if some in use and the local hosts
are multi-homed, will
actually obtain global IPv4 addresses NAT will not be in use. We
will not elaborate on this, as is common with VPN connections. the availability of global IPv4
addresses does not bring any additional complexity to the transition
mechanisms.

To enable this scenario, the gateway need needs to use a mechanism to
obtain a global IPv6 address prefix from the ISP, and advertise this
address prefix to the hosts in the unmanaged network; several
solutions will be assessed in a companion memo [EVAL].

5.2.3 Naming services in Case B

At this phase of

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In case B, hosts in the unmanaged domain have access to DNS services
through the gateway. As the gateway and the ISP both support IPv4
and IPv6, these services may be accessible by the IPv4 only IPv4-only hosts
using IPv4, by the IPv6-only hosts using IPv6, and by the dual stack
hosts using either. Currently, IPv4 only hosts usually discover the
IPv4 address of the local DNS server resolver using DHCP; there must be a
way for IPv6-only hosts to discover the IPv6 address of the DNS server.

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resolver.

There must be a way to resolve the name of local hosts to their IPv4
or IPv6 addresses. Typing auto-configured IPv6 addresses in a
configuration file is impractical; this implies either some form of
dynamic registration of IPv6 addresses in the local service, or a
dynamic address discovery mechanism. Possible solutions will be
compared in the evaluation draft.

The requirement to support server applications in the unmanaged
network implies a requirement to publish the IPv6 addresses of local
servers in the DNS. There are multiple solutions, including
variations of domain
name delegation. If we want to provide efficient reverse lookup functions, functions are to be
provided, delegation of a fraction of the ip6.arpa tree is also
required.

The response to a DNS request should not depend of on the protocol with by
which the request is transported: dual-stack hosts may indifferently use either
IPv4 or IPv6 to contact the local resolver; resolver, the choice of IPv4 or
IPv6 will may be random; random, and the value of the response should not depend
of a random event.

DNS transition issues in a dual IPv4/IPv6 network are discussed in
[DNSOPV6].

5.3 Case C, IPv6 connectivity without provider support

In this case the gateway is IPv6 capable, dual stack, but the ISP is not. The
gateway has been upgraded and offers both IPv4 and IPv6 connectivity
the hosts. It cannot rely on the ISP for IPv6 connectivity, because
the ISP does not offer ISP connectivity yet.

5.3.1 Application support in Case C

Application support in case C should be identical to that of case B.

5.3.2 Addresses and connectivity in Case C

The upgraded gateway will behave as an IPv6 router; it will continue
providing the IPv4 connectivity of non-upgraded connectivity, perhaps using NAT. Nodes in the
local network will obtain:

- IPv4 natted addresses, addresses (from or via the gateway),

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- IPv6 link local addresses,
- IPv6 global addresses.

The clients could also obtain IPv6 site local addresses, if the
gateway advertises a site local prefix; this raises the same issues
already discussed in case B.

There are two ways to bring immediate IPv6 connectivity on top of an
IPv4 only infrastructure: automatic tunnels tunnels, e.g. provided by the
[6TO4] technology, or configured tunnels. Both technologies have
advantages and limitations, which will be studied in a companion
document.

There will be some cases where the local hosts actually obtain
global IPv4 addresses. We will not discuss this scenario, as it does
not make the use of transition technology harder, or more complex.
Case A has already examined how hosts could obtain IPv6 connectivity
individually.

5.3.3 Naming services in Case C

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The local naming requirements in case C are identical to the local
naming requirements of case B, with two differences: delegation of
domain names, and management of reverse lookup queries.

A delegation of some domain name is required in order to publish the
IPv6 addresses of servers in the DNS. As the ISP does not provide
support for IPv6 in case C, the delegation mechanism will have to be
provided independently of the IP connectivity mechanism.

A specific mechanism for handling reverse lookup queries will be
required if the gateway uses a dynamic mechanism such as 6to4 to
obtain a prefix independently of any IPv6 ISP.

5.4 Case D, ISP stops providing native IPv4 connectivity

In this case the ISP is IPv6-only, so the gateway looses loses IPv4
connectivity, and is faced with an IPv6-only service provider. The
gateway itself is dual stack, and the unmanaged network includes
IPv4 only, IPv6-only and dual stack hosts. Any interaction between
hosts in the unmanaged network and IPv4 hosts on the Internet will
require the provision of some inter-protocol services by the ISP.

5.4.1 Application support in Case D

At this phase of the transition, IPv6 hosts can perform participate in all
types of applications with other IPv6 hosts. IPv4 hosts in the
unmanaged network will be able to perform local applications with
IPv4 or dual stack local hosts.

As in case B, we will assume that IPv6-only hosts will not interact
with IPv4-only hosts, either local or remote. We must however assume
that IPv4-only hosts and dual stack hosts will desire to interact
with IPv4 services available on the Internet: the inability to do so
would place the IPv6-only provider at a great commercial
disadvantage compared to other Internet service providers.

There are three possible ways that an ISP can provide hosts in the

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unmanaged network with access to IPv4 application: applications: by using a set
of application relays, by providing an address translation service,
or by providing IPv4-over-IPv6 tunnels. Our analysis concludes that
a tunnel service will seems to be vastly preferable.

We already mentioned the drawbacks of the application gateway
approach when analyzing case B: it is necessary to provide relays
for all applications, to develop a way to provision the hosts with
the addresses of these relays, and to modify the applications so
that they will only use the relays when needed. We also observe that
in an IPv6-only ISP the application relays would only be accessible
over IPv6, and would thus not be accessible by the "legacy" IPv4-
only hosts. The application relay approach is thus not very
attractive.

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Providing a network address and protocol translation service between
IPv6 and IPv4 would also have many drawbacks. As in case B, it will
have to be complemented by "application layer gateways" that will
rewrite references to IP addresses in the protocol; hosts may need
to be parameterized to use the translation service; and we would
have to solve DNS issues. In addition, in an IPv6-only ISP, an IPv6-
to-IPv4 translation service would not be accessible by legacy IPv4-
only hosts through the IPv6 only ISP service. The network level protocol translation
service appears doesn't appear to not be very desirable.

The proper preferable alternative to application relays and network address
translation is the provision of an IPv4-over-IPv6 service.

5.4.2 Addresses and connectivity in Case D

The ISP assigns an IPv6 prefix to the unmanaged network, so hosts
have a global IPv6 address and use it for global IPv6 connectivity.
This will require delegation of an IPv6 address prefix, as
investigated in case C.

To enable IPv4 hosts and dual stack host to access remote IPv4
services, the ISP must provide the gateway with at least one IPv4
address, using some form of IPv4-over-IPv6 tunneling. Once such
addresses have been provided, the gateway effectively acquires dual-
stack connectivity; for hosts inside the unmanaged network, this
will be indistinguishable from the IPv4 connectivity obtained in
case B or C.

5.4.3 Naming services in Case D

The loss of IPv4 connectivity has a direct impact on the provision
of naming services. An obvious consequence In many IPv4 unmanaged networks, hosts obtain
their DNS configuration parameters from the local gateway, typically
through the DHCP service. If the same mode of operation is desired
in case D, the gateway will have to be provisioned with the address
of a DNS server resolver and with other DNS parameters, and that this
provisioning will have to use IPv6 mechanisms. Another consequence
is that the DNS service in the gateway will only be able to use IPv6
connectivity to resolve queries; if local hosts perform DNS

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resolution autonomously, they will have the same restriction.

On the surface, this seems to indicate that the local hosts will
only be able to resolve names if the domain servers are accessible
through an IPv6 address documented in a an AAAA record. However, the
DNS services are just one case of "IPv4 servers accessed by IPv6
hosts": it should be possible to simply send queries through the
address translation
IPv4 connectivity services to reach the IPv4 only servers.

The gateway should be able to act as a "DNS proxy" recursive DNS name server for
the remaining IPv4 only hosts.

6 Security Considerations

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Security considerations are discussed as part of the applications'
requirements. They include:

- the guarantee that local applications are only used locally,
- the protection of the privacy of clients
- the requirement that peer-to-peer connections are only used by
authorized peers.

The security solutions currently used in IPv4 networks include a
combination of firewall functions in the gateway, authentication and
authorization functions in the applications, encryption and
authentication services provides by IP security, Transport Layer
Security and application specific services, and host-based security
products such as anti-virus software, and host firewalls. The
applicability of these tools in IPv6 unmanaged networks will be
studied in a companion document.

7 IANA Considerations

This memo does not include any request to IANA.

8 Copyright

The following copyright notice is copied from RFC 2026 [Bradner,
1996], Section 10.4, and describes the applicable copyright for this
document.

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other

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Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.

This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

9 Intellectual Property

The following notice is copied from RFC 2026 [Bradner, 1996],
Section 10.4, and describes the position of the IETF concerning
intellectual property claims made against this document.

The IETF takes no position regarding the validity or scope of any

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intellectual property or other rights that might be claimed to
pertain to the implementation or use other technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances
of licenses to be made available, or the result of an attempt made
to obtain a general license or permission for the use of such
proprietary rights by implementers or users of this specification
can be obtained from the IETF Secretariat.

The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.

10 Acknowledgements

This draft has benefited from the comments of the members of the
IETF V6OPS working group, and from extensive reviews by Chris
Fischer, Tony Hain, Suresh
K Satapati, Kurt Erik Lindqvist, Erik Nordmark, Pekka
Savola, and Margaret Wasserman.

11 References

Normative References

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[RFC791] J. Postel, "Internet Protocol", RFC 791, September 1981.

[RFC2460] Deering, S., and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.

[RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998.

[RFC2462] Narten, T., and S. Thomson, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.

Informative references

[EVAL] Evaluation of Transition Mechanisms for Unmanaged Networks,
work in progress.

[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
J., and E. Lear, "Address Allocation for Private Internets", RFC
1918, February 1996.

[RFC3056] Carpenter, B., and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.

[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.

[RFC3022] Srisuresh, P., and K. Egevang. "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, January 2001.

[RFC2993] T. Hain. "Architectural Implications of NAT", RFC 2993,
November 2000.

[RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day.
"Service Location Protocol, Version 2", RFC 2993, June 1999.

[RFC3041] Narten, T., and R. Draves. "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC 3041, January
2001.

[DNSOPV6] A. Durand. "IPv6 DNS transition issues", Work in progress.

[DNSINADDR] D. Senie. "Requiring DNS IN-ADDR Mapping", Work in
progress.

12 Authors' Addresses

Christian Huitema
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399

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Email: huitema@microsoft.com

Rob Austein
Email: sra@hactrn.net

Suresh Satapati
Cisco Systems, Inc.
San Jose, CA 95134
USA
EMail: satapati@cisco.com

Ronald van der Pol
NLnet Labs
Kruislaan 419
1098 VA Amsterdam
NL
Email: Ronald.vanderPol@surfnet.nl Ronald.vanderPol@nlnetlabs.nl

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Table of Contents:

1 Introduction .................................................... 1
2 Topology ........................................................ 1 2
3 Applications .................................................... 2 3
3.1 Local applications ............................................ 2 3
3.2 Client applications ........................................... 3
3.3 Peer-to-peer applications ..................................... 3
3.4 Server applications ........................................... 3 4
4 Application requirements of an IPv6 unmanaged network ........... 4
4.1 Requirements of local applications ............................ 4 5
4.2 Requirements of client applications ........................... 4 5
4.2.1 Privacy requirement of client applications .................. 5
4.3 Requirements of peer-to-peer applications ..................... 6
4.4 Requirements of server applications ........................... 6 7
5 Stages of IPv6 deployment ....................................... 7 8
5.1 Case A, host deployment of IPv6 applications .................. 7 8
5.1.1 Application support in Case A ............................... 8 9
5.1.2 Addresses and connectivity in Case A ........................ 8 9
5.1.3 Naming services in Case A ................................... 8 10
5.2 Case B, IPv6 connectivity with provider support ............... 9 10
5.2.1 Application support in Case B ............................... 9 10
5.2.2 Addresses and connectivity in Case B ........................ 10 11
5.2.3 Naming services in Case B ................................... 10 11
5.3 Case C, IPv6 connectivity without provider support ............ 11 12
5.3.1 Application support in Case C ............................... 11 12
5.3.2 Addresses and connectivity in Case C ........................ 11 12
5.3.3 Naming services in Case C ................................... 11 13
5.4 Case D, ISP stops providing native IPv4 connectivity .......... 12 13
5.4.1 Application support in Case D ............................... 12 13
5.4.2 Addresses and connectivity in Case D ........................ 13 14
5.4.3 Naming services in Case D ................................... 13 14
6 Security Considerations ......................................... 13 15
7 IANA Considerations ............................................. 14 15
8 Copyright ....................................................... 14 15
9 Intellectual Property ........................................... 14 16
10 Acknowledgements ............................................... 15 16
11 References ..................................................... 15 16
12 Authors' Addresses ............................................. 15 17

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