As per Relevance of the word document, we have this rfc below:
Network Working Group C.
Request for Comments: 3068
Category: Standards Track June 2001
An Anycast Prefix for 6to4 Relay
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (2001). All Rights Reserved
This memo introduces a "6to4 anycast address" in order to
the configuration of 6to4 routers. It also defines how this
will be used by 6to4 relay routers, how the corresponding "6to
anycast prefix" will be advertised in the IGP and in the EGP.
memo documents the reservation by IANA (Internet Assigned
Authority) of the "6to4 relay anycast prefix."
1
According to [RFC3056], there are two deployment options for a 6to
routing domain, depending on whether or not the domain is using
IPv6 exterior routing protocol. If a routing protocol is used,
the 6to4 routers acquire routes to all existing IPv6 networks
the combination of EGP and IGP. If no IPv6 exterior routing
is used, the 6to4 routers using a given relay router each have
default IPv6 route pointing to the relay router. This second case
typically used by small networks; for these networks, finding
configuring the default route is in practice a significant hurdle
In addition, even when the managers of these networks find
available route, this route often points to a router on the
side of the Internet, leading to very poor performance
The operation of 6to4 routers requires either that the
participate in IPv6 inter-domain routing, or that the routers
provisioned with a default route. This memo proposes a
method to define the default route. It introduces the IANA
"6to4 Relay anycast prefix" from which 6to4 packets will
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RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
automatically routed to the nearest available router. It allows
managers of the 6to4 relay routers to control the sources
to use their resource. It makes it easy to set up a large number
6to4 relay routers, thus enabling scalability
2
This memo uses the definitions introduced in [RFC3056], in
the definition of a 6to4 router and a 6to4 Relay Router. It adds
definition of the 6to4 Relay anycast prefix, 6to4 Relay
address, 6to4 IPv6 relay anycast address, and Equivalent IPv4
address
2.1 6to4 router (or 6to4 border router
An IPv6 router supporting a 6to4 pseudo-interface. It is
the border router between an IPv6 site and a wide-area IPv4 network
2.2 6to4 Relay
A 6to4 router configured to support transit routing between 6to
addresses and native IPv6 addresses
2.3 6to4 Relay anycast
An IPv4 address prefix used to advertise an IPv4 route to
available 6to4 Relay Router, as defined in this memo
The value of this prefix is 192.88.99.0/24
2.4 6to4 Relay anycast
An IPv4 address used to reach the nearest 6to4 Relay Router,
defined in this memo
The address corresponds to host number 1 in the 6to4 Relay
prefix, 192.88.99.1.
2.5 6to4 IPv6 relay anycast
The IPv6 address derived from the 6to4 Relay anycast
according to the rules defined in 6to4, using a null prefix and
null host identifier
The value of the address is "2002:c058:6301::".
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RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
2.6 Equivalent IPv4 unicast
A regular IPv4 address associated with a specific 6to4 Relay Router
Packets sent to that address are treated by the 6to4 Relay Router
if they had been sent to the 6to4 Relay anycast address
3 Model,
Operation of 6to4 routers in domains that don't run an IPv6
requires that these routers be configured with a default route to
IPv6 Internet. This route will be expressed as a 6to4 address.
packets bound to this route will be encapsulated in IPv4 whose
will be an IPv4 address associated to the 6to4 router, and
destination will be the IPv4 address that is extracted from
default route. We want to arrive at a model of operation in
the configuration is automatic
It should also be easy to set up a large number of 6to4
routers, in order to cope with the demand. The discovery of
nearest relay router should be automatic; if a router fails,
traffic should be automatically redirected to the nearest
router. The managers of the 6to4 relay routers should be able
control the sources authorized to use their resource
Anycast routing is known to cause operational issues: since
sending 6to4 router does not directly identify the specific 6to
relay router to which it forwards the packets, it is hard to
the responsible router in case of failure, in particular when
failure is transient or intermittent. Anycast solutions must
include adequate monitoring of the routers performing the service,
order to promptly detect and correct failures, and also
fault isolation procedures, in order to find out the
element when needed, e.g., following a user's complaint
4 Description of the
4.1 Default route in the 6to4
The 6to4 routers are configured with the default IPv6 route (::/0)
pointing to the 6to4 IPv6 anycast address
4.2 Behavior of 6to4 relay
The 6to4 relay routers that follow the specification of this
shall advertise the 6to4 anycast prefix, using the IGP of their IPv
autonomous system, as if it where a connection to an
network
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RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
The 6to4 relay routers that advertise the 6to4 anycast prefix
receive packets bound to the 6to4 anycast address. They will
these packets to the IPv6 Internet, as specified in [RFC3056].
Each 6to4 relay router that advertise the 6to4 anycast prefix
also provide an equivalent IPv4 unicast address. Packets sent
that unicast address will follow the same processing path as
sent to the anycast address, i.e., be relayed to the IPv6 Internet
4.3 Interaction with the
If the managers of an IPv4 autonomous domain that includes 6to4
routers want to make these routers available to neighbor ASes,
will advertise reachability of the 6to4 anycast prefix. When
advertisement is done using BGP, the initial AS path must contain
AS number of the announcing AS. The AS path should also include
indication of the actual router providing the service; there is
suggestion to perform this function by documenting the router'
equivalent IPv4 address in the BGP aggregator attribute of the path
further work is needed on this point
The path to the 6to4 anycast prefix may be propagated using
EGP procedures. The whole v6 network will appear to v4 as a
multi-homed network, with multiple access points scattered over
whole Internet
4.4 Monitoring of the 6to4 relay
Any 6to4 relay router corresponding to this specification
include a monitoring function, to check that the 6to4 relay
is operational. The router must stop injecting the route leading
the 6to4 anycast prefix immediately if it detects that the
function is not operational
The equivalent IPv4 address may be used to check remotely that
specific router is operational, e.g., by tunneling a test IPv6
through the router's equivalent unicast IPv4 address. When a
deploys several 6to4 relay routers, it is possible to build
centralized monitoring function by using the list of equivalent IPv
addresses of these routers
4.5 Fault
When an error is reported, e.g., by a user, the domain manager
be able to find the specific 6to4 relay router that is causing
problem. The first step of fault isolation is to retrieve
equivalent unicast IPv4 address of the router used by the user.
the router is located within the domain, this information will
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RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
to be retrieved from the IGP tables. If the service is
through a peering agreement with another domain, the information
be retrieved from the EGP data, e.g., the BGP path attributes
The second step is obviously to perform connectivity tests using
equivalent unicast IPv4 address
5 Discussion of the
The initial surfacing of the proposal in the NGTRANS working
helped us discover a number of issues, such as scaling concerns,
size of the address prefix, the need for an AS number, and
about risking to stay too long in a transition state
5.1 Does it scale ?
With the proposed scheme, it is easy to first deploy a small
of relay routers, which will carry the limited 6to4 traffic
the initial phases of IPv6 deployment. The routes to these
will be propagated according to standard peering agreements
As the demand for IPv6 increases, we expect that more ISPs
deploy 6to4 relay routers. Standard IPv4 routing procedures
direct the traffic to the nearest relay router, assuring
performance
5.2 Discovery and
The 6to4 routers send packets bound to the v6 Internet by
them to the 6to4 anycast address. These packets will reach
closest 6to4 relay router provided by their ISP, or by the
ISP according to inter-domain routing
The routes to the relay routers will be propagated according
standard IPv4 routing rules. This ensures automatic discovery
If a 6to4 relay router somehow breaks, or loses connectivity to
v6 Internet, it will cease to advertise reachability of the 6to
anycast prefix. At that point, the local IGP will
compute a route towards the "next best" 6to4 relay router. We
that adequate monitoring tools will be used to guarantee
discovery of connectivity losses
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RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
5.3 Access
Only those ASes that run 6to4 relay routers and are willing
provide access to the v6 network announce a path to the 6to4
prefix. They can use the existing structure of peering and
agreements to control to whom they are willing to provide service
and possibly to charge for the service
5.4 Why do we need a large prefix
In theory, a single IP address, a.k.a. a /32 prefix, would
sufficient: all IGPs, and even BGP, can carry routes that
arbitrarily specific. In practice, however, such routes are
guaranteed not to work
The size of the routing table is of great concern for the managers
Internet "default free" networks: they don't want to waste a
entry, which is an important resource, for the sole benefit of
small number of Internet nodes. Many have put in place filters
automatically drop the routes that are too specific; most of
filters are expressed as a function of the length of the
prefix, such as "my network will not accept advertisements for
network that is smaller than a /24." The actual limit may vary
network to network, and also over time
It could indeed be argued that using a large network is a waste
the precious addressing resource. However, this is a waste for
good cause of actually moving to IPv6, i.e., providing a real
to the address exhaustion problem
5.5 Do we need a specific AS number
A first version of this memo suggested the use of a specific
number to designate a virtual AS containing all the 6to4
routers. The rationale was to facilitate the registration of
access point in databases such as the RADB routing registry [RADB].
Further analysis has shown that this was not required for
operation
5.6 Will this slow down the move to IPv6 ?
Some have expressed a concern that, while the assignment of
anycast address to 6to4 access routers would make life a bit easier
it would also tend to leave things in a transition state
perpetuity. In fact, we believe that the opposite is true
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RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
A condition for easy migration out of the "tunnelling" state is
it be easy to have connectivity to the "real" IPv6 network;
means that people trust that opting for a real IPv6 address will
somehow result in lower performances. So the anycast
actually ensures that we don't stay in a perpetual transition
6 Future
Using a default route to reach the IPv6 Internet has a
drawback: the chosen relay may not be on the most direct path to
target v6 address. In fact, one might argue that, in the early
of deployment, a relay close to the 6to4 site would probably not
the site's ISP or the native destination's ISP...it would probably
some third party ISP's relay which would be used for transit and
have lousy connectivity. Using the relay closest to the
destination would more closely match the v4 route, and quite
provide a higher degree of reliability. A potential way to deal
this issue is to use a "redirection" procedure, by which the 6to
router learns the most appropriate route for a specific destination
This is left for further study
The practical operation of the 6to4 relay routers requires
development of monitoring and testing tools, and the elaboration
gradual management practices. While this document provides
guidelines for the design of tools and practice, we expect that
actual deployment will be guided by operational experience
7 Security
The generic security risks of 6to4 tunneling and the
protections are discussed in [RFC3056]. The anycast
introduces an additional risk, that a rogue router or a rogue
would introduce a bogus route to the 6to4 anycast prefix, and
divert the traffic. IPv4 network managers have to guarantee
integrity of their routing to the 6to4 anycast prefix in much
same way that they guarantee the integrity of the generic v4 routing
8 IANA
The purpose of this memo is to document the allocation by IANA of
IPv4 prefix dedicated to the 6to4 gateways to the native v6 Internet
there is no need for any recurring assignment
9. Intellectual
The following notice is copied from RFC 2026 [Bradner, 1996],
10.4, and describes the position of the IETF concerning
property claims made against this document
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RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
The IETF takes no position regarding the validity or scope of
intellectual property or other rights that might be claimed
pertain to the implementation or use other technology described
this document or the extent to which any license under such
might or might not be available; neither does it represent that
has made any effort to identify any such rights. Information on
IETF's procedures with respect to rights in standards-track
standards-related documentation can be found in BCP-11. Copies
claims of rights made available for publication and any assurances
licenses to be made available, or the result of an attempt made
obtain a general license or permission for the use of
proprietary rights by implementers or users of this specification
be obtained from the IETF Secretariat
The IETF invites any interested party to bring to its attention
copyrights, patents or patent applications, or other
rights which may cover technology that may be required to
this standard. Please address the information to the IETF
Director
10
The discussion presented here was triggered by a note that
Huntting sent to the NGTRANS and IPNG working groups. The
revived previous informal discussions, for which we have
acknowledge the members of the NGTRANS and IPNG working groups,
particular Scott Bradner, Randy Bush, Brian Carpenter, Steve Deering
Bob Fink, Tony Hain, Bill Manning, Keith Moore, Andrew Partan
Dave Thaler
11
[RFC3056] Carpenter, B. and K. Moore "Connection of IPv6 Domains
IPv4 Clouds", RFC 3056, February 2001.
[RADB] Introducing the RADB. Merit Networks
http://www.radb.net/docs/intro.html
12 Author's
Christian
Microsoft
One Microsoft
Redmond, WA 98052-6399
EMail: huitema@microsoft.
Huitema Standards Track [Page 8]
RFC 3068 An Anycast Prefix for 6to4 Relay Routers June 2001
13 Full Copyright
Copyright (C) The Internet Society (2001). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English
The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns
This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Funding for the RFC Editor function is currently provided by
Internet Society
Huitema Standards Track [Page 9]
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