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Network Working Group M. Bagnulo
Internet-Draft Huawei Labs at UC3M
Intended status: Informational F. Baker
Expires: November 14, 2008 Cisco Systems
I. van Beijnum
IMDEA Networks
May 13, 2008
IPv4/IPv6 Coexistence and Transition: Requirements for solutions
draft-ietf-v6ops-nat64-pb-statement-req-00
Status of this Memo
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This Internet-Draft will expire on November 14, 2008.
Abstract
This note presents the problem statement, analysis and requirements
for solutions to IPv4/IPv6 coexistence and eventual transition in a
scenario in which dual stack operation is not the norm.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem statement . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Transition scenarios . . . . . . . . . . . . . . . . . . . 3
2.1.1. Simple transition scenarios . . . . . . . . . . . . . 3
2.1.2. Transition scenarios that do not require
translation . . . . . . . . . . . . . . . . . . . . . 4
2.1.3. Transition scenarios that require translation . . . . 5
2.2. Requirements for the overall transition strategy . . . . . 6
3. Preliminary analysis for translation mechanisms . . . . . . . 7
3.1. Application behavior taxonomy . . . . . . . . . . . . . . 7
3.2. Placement of the NAT64 mechanisms . . . . . . . . . . . . 8
3.3. v4 addressing consideration . . . . . . . . . . . . . . . 9
3.4. Name-space considerations . . . . . . . . . . . . . . . . 10
3.5. Market timing considerations . . . . . . . . . . . . . . . 11
4. Requirements for new generation of v4-v6 translation
mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Basic Requirements that MUST be supported . . . . . . . . 11
4.2. Important things that SHOULD be supported . . . . . . . . 13
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
6. Security considerations . . . . . . . . . . . . . . . . . . . 14
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . . 15
8.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . . . . 17
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1. Introduction
This note addresses requirements for solutions to IPv4/IPv6
coexistence and eventual transition in a scenario in which dual stack
operation is not the norm.
2. Problem statement
Operationally, we now expect the transition to be less a matter of
connecting ever-growing IPv6 islands in an IPv4 network, and more a
matter of the network becoming a patchwork quilt of IPv4, IPv6, and
dual domains.
o Hosts now generally support IPv6 and IPv4 natively.
o As described in [RFC4213], the IETF community had expected
administrations to turn on IPv6 in their existing IPv4 networks,
resulting in a simple coexistence scenario.
o Increasingly, we hear statements that people want to move directly
to an IPv6-only or IPv6-dominant network.
In this context, "IPv6-only" refers to a network or system that only
runs IPv6, and "IPv6-dominant" refers to a network or system that may
use IPv4 internally or with other clients, but in the context only
routes IPv6 datagrams. "IPv4-only" and "IPv4-dominant" are defined
similarly. Since these are indistinguishable to the peer, the terms
"IPv4-only" and "IPv6-only" will be used in this paper and considered
to subsume the "dominant" issues.
2.1. Transition scenarios
There are six obvious transition scenarios:
o IPv4 system connecting to an IPv4 system across an IPv4 network,
o An IPv6 system connecting to an IPv6 system across an IPv6
network,
o an IPv4 system connecting to an IPv4 system across an IPv6
network,
o an IPv6 system connecting to an IPv6 system across an IPv4
network,
o an IPv4 system connecting to an IPv6 system, or
o an IPv6 system connecting to an IPv4 system.
2.1.1. Simple transition scenarios
The simplest coexistence cases are about an IPv4 system connecting to
an IPv4 system across an IPv4 network, or an IPv6 system connecting
to an IPv6 system across an IPv6 network. The dual stack case, in
which both endpoints and the relevant applications support IPv4 and
IPv6 and the network supports at least one of the protocols, falls
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into this case as the applications can connect using whichever stack
is consistent end to end.
The IETF strongly prefers and recommends this scenario, as the
operational matters are the simplest. Until the Internet reaches
IPv4 address exhaustion, an IPv4 and an IPv6 address can be assigned
to every interface, and the applications are supported. When it
becomes necessary to deploy only IPv6 addresses, since all other
systems have both, IPv6-only systems cleanly interoperate with
existing systems.
2.1.2. Transition scenarios that do not require translation
[RFC4213] discusses the scenario in Figure 1, in which routers
connect two dual domains via an IPv4-only domain. Obviously, this
can be reversed: routers can connect two dual domains via an IPv6-
only domain. Note that the connecting domain need not actually be
IPv4-only or IPv6-only; to create this scenario, it need merely fail
to offer IPv6 or IPv4 services to the neighboring domains.
,-. ,-. ,-.
,' `. ,' `. ,' `.
; : ; : ; :
; IPv4+ : ; IPv4- : ; IPv4+ :
; IPv6 : ; only : ; IPv6 :
; Domain : ; Domain : ; Domain :
; : ; : ; :
| +----+ | | +----+ | | +----+ |
| |IPv4| | | |IPv4| | | |IPv4| |
| |Host+ | | |Host| | | |Host| |
: +----+\ ; : /+----+\ ; :/ +----+ ;
: +----+ \+------+ +------+ +----+ ;
: |IPv6+--+Router+=======+Router+-+IPv6| ;
:|Host| ;+------+ +------+:|Host| ;
:+----+ ; : ; :+----+ ;
`. ,' `. ,' `. ,'
`-' `-' `-'
Figure 1: Disconnected continuity
In such a scenario, there are two obvious solutions: one can tunnel
across the connecting domain, as shown, or one can translate between
IP layers using something akin to traditional NAT technology. The
tunnel approach offers some pros and some cons: it natively connects
the dual domains, meaning that all applications should work, but they
may have issues with the path MTU, and the tunnels require some form
of configuration. The NAT approach similarly offers pros and cons:
it offers something similar to standard routing, but it suffers from
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the various ills of Network Address Translation on both sides,
meaning that it may be difficult for the dual domains to offer
services to each other.
In general, the IETF recommends the use of tunnels rather than a dual
NAT.
There are at least three generic models that could be used to
describe this kind of tunneling scenario:
o Static tunnels with interior dynamic routing
o Start-time negotiated tunnels to some central point with default
routing (example in [I-D.stenberg-v6ops-pd-route-maintenance])
o Dynamic tunnels with specific routing to islands (examples might
include ISATAP [RFC4214] or a tunnel broker of some description)
Static tunnels with routing through them are commonly deployed today,
both in VPNs and in overlay networks. The positive side is that they
provide simple service; the negative is that the generally require
manual configuration and can result in suboptimal routing.
A "start-time" tunnel might be useful in an access network that
serves homes or SOHO environments. In this model, the ISP informs
the CPE of a cross-network peer that it can create a tunnel to,
reducing the case to one similar to static tunneling but without
manual configuration.
A dynamic tunneling environment is an overlay model in which systems
create tunnels to various peers across the connecting domain as
needed, based on a priori knowledge of the correlation between remote
prefixes and next hop routers. This has not been adequately
described at this point, and therefore involves complexities in
implementation and deployment.
2.1.3. Transition scenarios that require translation
Translation, as found in Figure 2, is considered in NAT-PT [RFC2766],
which has in turn been set aside via [RFC4966]. In essence,
translation is required when an IPv4-only system connects to an IPv6-
only system or an IPv6-only system connects to an IPv4-only system.
These systems need not actually be IPv4-only or IPv6-only; if the
connecting network is IPv4-only or IPv6-only and provides no tunnel,
but only offers IPv4 service to one and only offers IPv6 service to
the other, the situation is equivalent.
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,-----. ,-----.
,' `. ,' `.
/ \ / \
/ IPv4-only \ / IPv6-only \
/ Domain +-----------+ Domain \
; |Translation| :
| | Gateway | |
: +-----------+ ;
\ +----+ / \ +----+ /
\ |IPv4| / \ |IPv6| /
\ |Host| / \ |Host| /
`. +----+,' `. +----+,'
'-----' '-----'
Figure 2: Translation
In such a scenario, it is necessary for the network to create a
translation gateway, at which datagrams from one system are
translated forwarded to the other. The situation is in many ways
reflexive, since most Internet sessions are bidirectional - TCP
between an IPv4 and an IPv6 system translate data messages in one
direction and acknowledgments in the other.
They are not reflexive, however, in the distribution of domain names.
If the application is client-server and the server is in one of the
domains, the name of the server need only be propagated to the other.
Reverse lookups, frequently used in spam verification would require
the client's name to be propagated into the server's domain. But in
this there are issues. The address of the client (the TCP peer) as
seen by the server is not the remote system in the other domain; it
is the translator. This is readily worked around for an IPv6 server,
as the IPv4 address of the remote peer can be embedded in a "privacy"
address [RFC4941], making the reverse lookup viable. This doesn't
work on the IPv4 side, however.
2.2. Requirements for the overall transition strategy
Given the problem statement presented here, we see the following
requirements for a complete transition strategy:
1. Any transition strategy must contemplate a period of coexistence,
with ultimate transition (e.g., turning off IPv4) being a
business decision.
2. Many are delaying turning on IPv6 (initiating coexistence in
their networks) as long as possible.
3. Some are turning off IPv4 immediately, at least as a customer
service.
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4. Therefore, dual stack approaches, tunneled architectures, and
translation architectures are all on the table.
5. Any solution that makes translation between semi-connected
islands "normal" has failed the fundamental architecture of the
Internet and can expect service complexity to be an issue.
[RFC3439]
6. Translation architectures must provide for the advertisement of
IPv4 names to IPv6 systems and vice versa. The address
advertised in the "far" domain must be that of the translating
gateway.
7. Tunneling architectures must provide a way to minimize and
ideally eliminate configuration of the tunnel.
3. Preliminary analysis for translation mechanisms
3.1. Application behavior taxonomy
The general purpose of NAT64 type of mechanisms is to enable
communication between a v4-only node and a v6-only node. However,
there is wide range of type of communications, when considering how
they handle IP addresses. So, in order to properly characterize the
problem, we need to do an analysis of the different application
behavior in terms of the usage of their IP addresses. We will next
present a taxonomy of the behavior of the application with respect of
how they use the IP address. The support of the different type of
behavior will impose a different set of constraints to the design of
a NAT64 mechanisms. It is then important to decide which type of
application behavior will be supported before starting to design a
NAT64 mechanism. The proposed taxonomy is heavily based on the one
presented in section 1.1 of draft-ietf-shim6-app-refer-00.txt.
The proposed application behavior taxonomy is the following:
Short-lived local handle. The IP addresses is never retained by the
application. The only usage is for the application to pass it from
the DNS APIs (e.g., getaddrinfo()) and the API to the protocol stack
(e.g., connect() or sendto()). This type of communication can be
either initiated by the v4-only node or by the v6-only node,
resulting in two type of behaviors, v4-initiated short lived local
handle and v6-initiated short lived local handle.
Long-lived application associations. The IP address is retained by
the application for several instances of communication. However, it
is always the same node that initiates the communication. This type
of communication can be either initiated by the v4-only node or by
the v6-only node, resulting in two type of behaviors, v4-initiated
long-lived associations and v6-initiated long-lived associations.
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Callbacks. The application at one end retrieves the IP address of
the peer and uses that to later communicate "back" to the peer. This
type of communication can be either initiated by the v4-only node or
by the v6-only node, resulting in two type of behaviors, v4-initiated
callback, meaning that the initial communication is initiated by the
v6-only node, and later the v4-only node initiates the callback, and
v6-initiated callback, meaning that the initial communication is
initiated by the v4-only node, and later the v6-only node initiates
the callback. An additional disticntion can be made based on the
time-frame of the call back operation. There can be short-lived
call-backs, where the receiver inmediatelly calls back to the
initiator and long-lived call-backs where the receiver calls backs
after a while.
Referrals. In an application with more than two parties, party B
takes the IP address of party A and passes that to party C. After
this party C uses the IP address to communicate with A. In this type
of communication, the following 6 sub-cases are possible.
o A and B are v6-only nodes and C is a v4-only node;
o A and C are v6-only nodes and B is a v4-only node,
o B and C are v6-only nodes and A is a v4-only node,
o A and B are v4-only nodes and C is a v6-only node;
o A and C are v4-only nodes and B is a v6-only node,
o B and C are v4-only nodes and A is a v6-only node,
"Identity" comparison. Some applications might retain the IP
address, not as a means to initiate communication as in the above
cases, but as a means to compare whether a peer is the same as
another peer. While this is insecure in general, it might be
something which is used e.g., when TLS is used. This type of
communication results in two sub-cases, when the v4-only node
performs comparison of the v6-only node identity, and when the v6-
only node performs comparison of the v4-only node identity
3.2. Placement of the NAT64 mechanisms
Another aspect that is critical to design a NAT64 mechanism is the
placement of the mechanisms involved. In other words, what elements
can be modified/updated to support the NAT64 mechanisms. We assume
that the NAT64 box supports a set of mechanisms that are the core
part of the solution, but some approaches may require the
modification of additional elements. In particular, we can identify
the following additional elements that may require modification to
support a NAT64 approach.
Modification to v4-only nodes: one option is to require modification
to existent v4-only nodes in order to support the NAT64 mechanism.
This option would impose high deployment costs, because the existent
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base of v4-only nodes is really big and there is no incentives for
the v4-only nodes to install such mechanism, since it seems unlikely
that v4-only nodes will have a strong need to communicate with v6-
only nodes (at least at the initial stages of v6 deployment).
However, it may be possible that this is the only viable solution for
supporting some type of application behavior.
Modification to v6-only nodes: Another option is to require
modifications to v6-only nodes. This option seems much more
acceptable, since the existent base of v6-nodes is relatively small
and there would be a strong incentive for v6-only nodes to
communicate with v4-only nodes, since most of the contents are
available only in v4 today. However, imposing modifications to v6-
only nodes does make deployment of the solution more difficult, since
update of current v6-implementations is needed. In addition, there
is an architectural consideration, that we would be imposing v6-only
nodes to support "NAT hacks" in order to enable communication with
the v4 world, and that those modifications may stay forever, even
when the need for communication with the v4-Internet is not so
pressing.
Modification to both v4-only nodes and v6-only nodes. Another option
is to require updates to both v4-only nodes and also to v6-only
nodes. Needless to say that this would be the option with higher
deployment costs.
No modification. Another option is that the NAT64 mechanisms does
not require modification to any host and that the mechanism is fully
contained in the NAT64 box. This was the case of the previously
defined NAT-PT approach. However, it may be challenging to design a
solution with this constraint that does not suffer the limitations
suffered by the NAT-PT mechanism that lead the IETF community to
deprecate it.
Another consideration related to the modification imposed by a NAT64
approach is about what elements in the nodes need to be updated. In
particular, it is important to determine if only the IP layer on the
affected nodes needs to be modified or f other elements in the nodes
needs to be updated. In particular, it is critical to determine if
applications need to e modified in order to support the NAT64
mechanism.
3.3. v4 addressing consideration
We assume that both the v6-only nodes and the v6 interface of the
NAT64 boxes will have routable IPv6 addresses. However, on the v4
side, there are more options. Either the v4 interface of the NAT64
boxes and/or the v4-only nodes can have either v4 private addresses
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or v4 public addresses. Actually, it is possible that the different
combinations make sense. It seems clear that the case where public
v4 addresses are used in both the v4 interface of the NAT64 box and
the v4-only nodes is relevant. The case where the v4-only node has a
private v4 address and the NAT64 box has a public address seems also
possible, but here it seems reasonable to assume that a NAT box will
exist between the v4 only node and the NAT64 box. The case where
both the v4 node and the NAT64 box have v4 private addresses could
also make sense, since this could apply to a scenario where a site
that has v4 private addresses and v6 addresses could try to use a
NAT64 box internally. The last case, where the v4 node has public
address and the NAT64 box has a private address seems harder to
justify though.
Another consideration related to v4 addressing of the NAT64 approach
is the number of addresses required by the NAT64 box. It is possible
that some NAT64 approaches require a pool of v4 addresses instead of
a single v4 address. Considering the status of the v4 address space
consumption, it may not be feasible to use a NAT64 approach that
require a big number of v4 public addresses.
3.4. Name-space considerations
One of the major choices that are faced when designing a NAT4
mechanism that enable communication initiated by the v4-only node
towards a v6-only node. In this case, the v4 only node needs to
identify the v6 only node and the problem is that there is no means
to permanently map the v6 address space in the v4 address space. So
in order to enable a v4-only node to identify a v6-only node a name
space other than the IPv4 address space is needed. We will next
discuss some options that could be considered to identify v6 nodes in
the v4 world.
A first option is to use IPv4 addresses to identify IPv6 nodes. The
problem is that the v6 address space is much bigger than the v4
address space, so it is not possible to do permanent mapping between
these two. This basically implies that dynamic mapping between a
given v4 address and different v6 addresses are established. While
this works for some type of application behavior, it does not support
others, such as communications initiated by a v4 node towards a v6
node in a general case (it is possible for a given subset of v6
nodes, but not as a general solution)
A second option is to use IPv6 addresses themselves. In this case,
the IPv4 node is aware of the IPv6 address of the destination and it
uses it to identify the target at the NAT64 box. This option would
likely imply modifications in the v4 nodes.
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A third option is to use FQDN to identify nodes. In this case v4
nodes identify v6 nodes using FQDNs, which is already supported in
the v4 world. The difficulties with such a approach is that DNS ALG
are likely to be required.
A fourth option is to use a combination of IPv4 address, transport
protocol and port for identification of a v6 node or a v6 flow.
3.5. Market timing considerations
We expect translation mechanism to require deployment in the very
near term, prior to IPv4 address depletion, and to be interoperable
with end systems that have been deployed in that timeframe. Since
address space depletion is expected t occur in the 2010-2012
timeframe and host software tends to be changed primarily when people
buy new hardware (every 2-3 years on average), we expect that this
needs to be compatible with currently-deployed Windows (XP and
Vista), MacOSX (Tiger and Leopard), Linux, and Solaris operating
systems. That argues for a solution that requires no changes to host
software that cannot be reasonably expected to deploy via patch
update procedures - this is otherwise all solved in network devices.
4. Requirements for new generation of v4-v6 translation mechanisms
This list of requirements basically should contain all the aspects
that should be considered when designing a new generation of
translation mechanisms.
4.1. Basic Requirements that MUST be supported
These are the requirements for short term mechanism behaviour
R1: Changes in the hosts
The translation mechanism MUST NOT require changes in the v4-only
nodes to support the Basic requirements described in this section,
unless explicitly stated in the particular requirement. The
translation mechanism MAY require changes to v6-only nodes.
R2: Basic communication support
o R2.1: Translation mechanim must support v6-initiated short-lived
local handle (as defined in Section 3.1. (strong consensus on
this)
o R2.2: Translation mechanim must support v4-initiated short-lived
local handle (as defined in Section 3.1). (not clear if there is
consensus for this)
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o R2.2.1: v4 initiators can either use IPv4 public addresses or IPv4
private addresses and use a NAT.(The acceptance of R2.2.1 is
subject to the acceptance of R2.2.
R3: Interaction with dual-stack hosts
Translation mechanism MUST allow using native connectivity when it is
available. This means that if a v6-only nodes wants to communicate
with a dual stack, it must use native v6 connectivity and if a v4-
only nodes wants to communicate with a dual stack, it must use native
v4 connectivity.(In this case, dual stack means a host with both IPv6
and IPv4 stacks, wich are both active, i.e. they have v4 and v6
connectivity).
R4: DNS semantics preservation
Any modifications to DNS responses associated with translation MUST
NOT violate standard DNS semantics. This includes in particular that
a DNS response (that has been modified by the translator mechanism)
should not be invalid if it ends up in the wrong context, i.e.
traversing a non expected part of the topology.
R5: Routing
IPv6 routing should not be affected in any way, and there should be
no risk of importing "entropy" from the IPv4 routing tables into
IPv6.
R6: Protocols supported
The translation mechanism MUST support at least TCP, UDP, ICMP, TLS.
R7: Behave requirements
The translation mechanism MUST be compliant with the requirements for
IPv4 NATs defined in [I-D.ietf-behave-tcp] and in [RFC4787] when
applicable. These requirements should be interpreted with the IPv6
side on the IPv6-IPv4 translator being the IPv4 private side of the
conventional NAT.
R8: Fragmented packets
The translation mechanism MUST suport fragmented packets when the
fragments arrive within an interval smaller or equal to 5 seconds.
However, the translator device MUST avoid that the support for
fragmented packets introduces a DoS attack vector (i.e. an attacker
injecting a high number of fragments would result in a DoS attack to
the device), so the device MUST implement some form of limitation to
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the resources used by the fragmented packet support. for example a
translator device may define a maximum amount of memory used for
storing fragmented packet state (the actual amount of memory will
depend on the intended usage of the box, carrier grade vs. set top
box).
R9: Security
The adoption of the translation mechanism MUST not result in a
significantly more vulnerable Internet
R10: DNSSec support
DNSSec support MUST NOT be prevented.
o R10.1: In particular, if an IPv6 node is initiating a
communication with an IPv4 that is located behind a translator,
the IPv6 initiator MUST be able to perform DNSSec verification of
the DNS information of the IPv4 target. (strong consensus on this
one).
o R10.2: In particular, if an IPv4 node is initiating a
communication with an IPv6 that is located behind a translator,
the IPv4 initiator MUST be able to perform DNSSec verification of
the DNS information of the IPv4 target. This may require the
modification of the IPv4 node as well. (not clear if there
consensus on this one)
R11: IPsec support.
The translator MUST support communication between IPv4 node and IPv6
node using UDP Encapsulation of IPsec ESP Packets as defined in
[RFC3948] as applicable. RFC3948 should be interpreted as with the
IPv6 side on the IPv6-IPv4 translator being the IPv4 private side of
the conventional NAT. IPsec support MAY require updating also the
IPv4 side.
4.2. Important things that SHOULD be supported
I2: Operational flxibility
It should be possible to locate the translation device at an
arbitrary point in the network (i.e. not at fixed points such as a
site exit), so that there is full operational flexibility.
I3: Central Management
Any configuration need for an IPv6 host to make use of the mechanism
should be possible centrally, e.g. a DHCP option.
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I4: Richer application behaviour support
The translation mechanism SHOULD support the other types of
application behaviours, including Long-lived application
associations, callbacks and referrals.In order to support this. the
translation mechanism MAY require changes to v4-only nodes too
I5: MIPv6 support
The translation mechanism SHOULD not prevent MIPv6 Route Optimization
when the CN is a v4-only node
I6: SCTP support
The translation mechanism SHOULD not prevent a SCTP communication
between a v6-only node and a v4-only node
I7: DCCP support
The translation mechanism SHOULD not prevent a DCCP communication
between a v6-only node and a v4-only node
I8: Multicast support
The translation mechanism SHOULD not prevent multicast traffic
between the v4-only nodes and the v6-only nodes.
5. Contributors
This draft contains contributions from Iljitsch van Beijnum, Brian
Carpenter and Elwyn Davies (this doesn't mean that they agree on the
draft, just that we have used text provided by them). We would like
to acknowledge the comments from Dave Thaler, Michael Richardson,
George Tsirtsis, Hesham Soliman, Yaron Sheffer and Kurt Lindqvist.
6. Security considerations
The requirements include R9 and R11 concerning security issues.
7. Acknowledgments
Marcelo Bagnulo is partly funded by Trilogy, a research project
supported by the European Commission under its Seventh Framework
Program.
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8. References
8.1. Normative References
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.
[RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/
Co-existence Security Considerations", RFC 4942,
September 2007.
[I-D.ietf-behave-tcp]
Guha, S., "NAT Behavioral Requirements for TCP",
draft-ietf-behave-tcp-07 (work in progress), April 2007.
[RFC4787] Audet, F. and C. Jennings, "Network Address Translation
(NAT) Behavioral Requirements for Unicast UDP", BCP 127,
RFC 4787, January 2007.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets",
RFC 3948, January 2005.
8.2. Informative References
[RFC3439] Bush, R. and D. Meyer, "Some Internet Architectural
Guidelines and Philosophy", RFC 3439, December 2002.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC4214] Templin, F., Gleeson, T., Talwar, M., and D. Thaler,
"Intra-Site Automatic Tunnel Addressing Protocol
(ISATAP)", RFC 4214, October 2005.
[RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address
Translation - Protocol Translation (NAT-PT)", RFC 2766,
February 2000.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
[RFC4966] Aoun, C. and E. Davies, "Reasons to Move the Network
Address Translator - Protocol Translator (NAT-PT) to
Historic Status", RFC 4966, July 2007.
[I-D.stenberg-v6ops-pd-route-maintenance]
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Stenberg, M. and O. Troan, "IPv6 Prefix Delegation routing
state maintenance approaches",
draft-stenberg-v6ops-pd-route-maintenance-00 (work in
progress), December 2007.
Authors' Addresses
Marcelo Bagnulo
Huawei Labs at Universidad Carlos III de Madrid
Av. Universidad 30
Leganes, Madrid 28911
SPAIN
Phone: 34 91 6249500
Email: marcelo@it.uc3m.es
URI: http://www.it.uc3m.es
Fred Baker
Cisco Systems
Santa Barbara, California 93117
USA
Phone: +1-408-526-4257
Fax: +1-413-473-2403
Email: fred@cisco.com
Iljitsch van Beijnum
IMDEA Networks
Madrid, Madrid 28911
Spain
Phone:
Fax:
Email: iljitsch@muada.com
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