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Network Working Group A. Durand Request for Comments: 2546 IMAG Category: Informational B. Buclin

                                                      AT&T Labs Europe
                                                            March 1999
                       6Bone Routing Practice

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

1. Introduction

 The 6Bone is an environment supporting experimentation with the IPv6
 protocols and products implementing it. As the network grows, the
 need for common operation rules emerged. In particular, operation of
 the 6Bone backbone is a challenge due to the frequent insertion of
 bogus routes by leaf or even backbone sites.
 This memo identifies guidelines on how 6Bone sites might operate, so
 that the 6Bone can remain a quality experimentation environment and
 to avoid pathological situations that have been encountered in the
 past. It defines the 'best current practice' acceptable in the 6Bone
 for the configuration of both Interior Gateway Protocols (such as
 RIPng [RFC 2080]) and Exterior Gateway Protocols (like BGP4+ [RFC
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 document are to be interpreted as described in [RFC 2119].

2. Basic principles

 The 6Bone is structured as a hierarchical network with pseudo Top
 Level Aggregator (pTLA) sites, pseudo Next Level Aggregator (pNLA)
 sites and leaf sites. This topology supports the IPv6 address
 aggregation architecture as described in [1]. The 6Bone backbone is
 made of a mesh interconnecting pTLAs only. pNLAs connect to one or
 more pTLAs and provide transit service for leaf sites.

Durand & Buclin Informational [Page 1] RFC 2546 6Bone Routing Practice March 1999

 pTLA sites MUST use BGP4+ [RFC 2283] as the mandatory routing
 protocol for exchanging routing information among them.
 Multi-homed sites or pNLAs SHOULD also use BGP4+. Regular sites MAY
 use a simple default route to their ISP.

3. Common Rules

 This section details common rules governing the routing on the 6Bone.
 They are derived from issues encountered on the 6Bone, with respect
 to the routes advertised, handling of special addresses, and
  1) link local prefixes
  2) site local prefixes
  3) loopback prefix & unspecified prefix
  4) multicast prefixes
  5) IPv4-compatible prefixes
  6) IPv4-mapped prefixes
  7) default routes
  8) Yet undefined unicast prefixes (from a different /3 prefix)
  9) Inter site links issues
  10) aggregation & advertisement issues

3.1 Link-local prefix

 The link-local prefix (FE80::/10) MUST NOT be advertised through
 either an IGP or an EGP.
 By definition, the link-local prefix has a scope limited to a
 specific link. Since the prefix is the same on all IPv6 links,
 advertising it in any routing protocol does not make sense and,
 worse, may introduce nasty error conditions.
 Well known cases where link local prefixes could be advertised by
 mistake include:

Durand & Buclin Informational [Page 2] RFC 2546 6Bone Routing Practice March 1999

  1. a router advertising all directly connected network prefixes

including the link-local one.

  1. Subnetting of the link-local prefix.
 In such cases, vendors should be urged to correct their code.

3.2 Site-local prefixes

 Site local prefixes (in the FEC0::/10 range) MAY be advertized by
 IGPs or EGPs within a site. The precise definition of a site is
 ongoing work discussed in the IPng working group.
 Site local prefixes MUST NOT be advertised to transit pNLAs or pTLAs.

3.3 Loopback and unspecified prefixes

 The loopback prefix (::1/128) and the unspecified prefix (::0/128)
 MUST NOT be advertised by any routing protocol.

3.4 Multicast prefixes

 Multicast prefixes MUST NOT be advertised by any unicast routing
 protocol.  Multicast routing protocols are designed to respect the
 semantics of multicast and MUST therefore be used to route packets
 with multicast destination addresses (in the range FF00::/8).
 Multicast address scopes MUST be respected on the 6Bone. Only global
 scope multicast addresses MAY be routed across transit pNLAs and
 pTLAs. There is no requirement on a pTLA to route multicast packets.
 Organization-local multicasts (in the FF08::/16 or FF18::/16 ranges)
 MAY be routed across a pNLA to its leaf sites.
 Site-local multicasts MUST NOT be routed toward transit pNLAs or
 Obviously, link-local multicasts and node-local multicasts MUST NOT
 be routed at all.

3.5 IPv4-compatible prefixes

 Sites may choose to use IPv4 compatible addresses (::a.b.c.d)
 internally.  As there is no real rationale today for doing that,
 these addresses SHOULD
 NOT be used in the 6Bone.

Durand & Buclin Informational [Page 3] RFC 2546 6Bone Routing Practice March 1999

 The ::/96 IPv4-compatible prefixes MAY be advertised by IGPs.
 IPv4-compatible prefixes MUST NOT be advertised by EGPs to transit
 pNLAs or pTLAs.

3.6 IPv4-mapped prefixes

 IPv4-mapped prefixes (::FFFF:a.b.c.d where a.b.c.d is an IPv4
 address) MAY be advertised by IGPs within a site. It may be useful
 for some IPv6 only nodes within a site to have such a route pointing
 to a translation device.
 IPv4-mapped prefixes MUST NOT be advertised by EGPs.

3.7 Default routes

 6Bone core pTLA routers MUST be default-free.
 pTLAs MAY advertise a default route to their pNLAs. Transit pNLAs MAY
 do the same for their leaf sites.

3.8 Yet undefined unicast prefixes

 Yet undefined unicast prefixes from a format prefix other than
 2000::/3 MUST NOT be advertised by any routing protocol in the 6Bone.
 In particular, RFC 2471 test addresses MUST NOT be advertised on the
 Routing of global unicast prefixes outside of the 6Bone range
 (3FFE::/16) is discussed in section 4, Routing policies, below.

3.9 Inter-site links

 Global IPv6 addresses MUST be used for the end points of the inter-
 site links. In particular, IPv4 compatible addresses MUST NOT be used
 for tunnels.
 Prefixes for those links MUST NOT be injected in the global routing

3.10 Aggregation & advertisement issues

 Route aggregation MUST be performed by any border router.
 Sites or pNLAs MUST only advertise to their upstream provider the
 prefixes assigned by that ISP unless otherwise agreed.

Durand & Buclin Informational [Page 4] RFC 2546 6Bone Routing Practice March 1999

 Site border router MUST NOT advertise prefixes more specific than the
 /48 ones allocated by their ISP.
 pTLA MUST NOT advertise prefixes longer than 24 to other pTLAs unless
 special peering agreements are implemented. When such special peering
 agreements are in place between any two or more pTLAs, care MUST be
 taken not to leak the more specific prefixes to other pTLAs not
 participating in the peering agreement.

4. Routing policies

 6Bone backbone sites maintain the mesh into the backbone and provide
 an as reliable as possible service, granted the 6Bone is an
 experimentation tool.  To achieve their mission, 6Bone backbone sites
 MUST maintain peerings with at least 3 (three) other back bone sites.
 The peering agreements across the 6Bone are by nature non-commercial,
 and therefore SHOULD allow transit traffic through.
 Eventually, the Internet registries will assign other TLAs than the
 6Bone one (currently 3FFE::/16). The organizations bearing those TLAs
 will establish a new IPv6 network, parallel to the 6Bone. The 6Bone
 MIGHT interconnect with this new IPv6 Internet, b ut transit across
 the 6Bone will not be guaranteed. It will be left to each 6Bone
 backbone site to decide whether it will carry traffic to or from the
 IPv6 Internet.

5. The 6Bone registry

 The 6Bone registry is a RIPE-181 database with IPv6 extensions used
 to store information about the 6Bone. Each 6Bone site MUST maintain
 the relevant entries in the 6Bone registry ( In
 particular, the following objects MUST be present:
  1. IPv6-site: site description
  1. Inet6num: prefix delegation
  1. Mntner: coordinate of site maintenance staff
 Other objects MAY be maintained at the discretion of the sites, such
 as routing policy descriptors, person or role objects. The Mntner
 object MUST make reference to a role or person object, but those must
 not necessarily reside in the 6Bone registry, they can be stored
 within any of the Internet registry databases (RIPE, InterNIC, APNIC,

Durand & Buclin Informational [Page 5] RFC 2546 6Bone Routing Practice March 1999

6. Guidelines for new sites joining the 6Bone

 New sites joining the 6Bone should seek to connect to a transit pNLA
 or a pTLA within their region, and preferably as close as possible to
 their existing IPv4 physical and routing path for Internet service.
 The 6Bone registry is available to find out candidate ISPs.
 Any site connected to the 6Bone MUST maintain a DNS server for
 forward name looking and reverse address translation. The joining
 site MUST maintain the 6Bone registry objects relative to its site,
 and in particular the IPv6- site and the MNTNER objects.
 The upstream ISP MUST delegate the reverse address translation zone
 in DNS to the joining site. The ISP MUST also create 6Bone registry
 objects reflecting the delegated address space (inet6num:).
 Up to date information about how to join the 6Bone is available on
 the 6Bone Web site at

7. Guidelines for 6Bone pTLA sites

 6Bone pTLA sites are altogether forming the backbone of the 6Bone. In
 order to ensure the highest level possible of availability and
 stability for the 6Bone environment, a few constraints are placed
 onto sites wishing to become or stay a 6Bone pTLA:
 1. The site MUST have experience with IPv6 on the 6Bone, at least as
    a leaf site and preferably as a transit pNLA under an existing
 2. The site MUST have the ability and intent to provide "production-
    like" 6Bone backbone service to provide a robust and operationally
    reliable 6Bone backbone.
 3. The site MUST have a potential "user community" that would be
    served by becoming a pTLA, e.g., the requester is a major player
    in a region, country or focus of interest.
 4. Must commit to abide by the 6Bone backbone operational rules and
    policies as defined in the present document.
 When a candidate site seeks to become a pTLA site, it will apply for
 it to the 6Bone Operations group (see below) by bringing evidences it
 meets the above criteria.

Durand & Buclin Informational [Page 6] RFC 2546 6Bone Routing Practice March 1999

8. 6Bone Operations group

 The 6Bone Operations group is the body in charge of monitoring the
 adherence to the present rules, and will take the appropriate actions
 to correct deviations. Membership in the 6Bone Operations group is
 mandatory for, and restricted to, any site connected to the 6Bone.
 The 6Bone Operations group is currently defined by those members of
 the existing 6Bone mailing list, i.e.,, who represent
 sites participating on the 6Bone. Therefore it is incumbent on
 relevant site contacts to join the mailing list. Instructions on how
 to join the list are maintained on the 6Bone web site at

9. Common rules enforcement

 Participation in the 6Bone is a voluntary and benevolent undertaking.
 However, participating sites are expected to adhere to the rules
 described in this document, in order to maintain the 6Bone as quality
 tool for experimenting with the IPv6 protocols and products
 implementing them.
 The following processes are proposed to help enforcing the 6Bone
  1. Each pTLA site has committed when requesting their pTLA to

implement the rules, and to ensure they are respected by sites

   within their administrative control (i.e. those to who prefixes
   have been delegated).
  1. When a site detects an issue, it will first use the 6Bone registry

to contact the site maintainer and work the issue.

  1. If nothing happens, or there is disagreement on what the right

solution is, the issue can be brought to the 6Bone Operations

  1. When the problem is related to a product issue, the site(s)

involved is responsible for contact the product vendor and work

   toward its resolution.
  1. When an issue causes major operational problems, backbone sites may

decide to temporarily set filters in order to restore service.

Durand & Buclin Informational [Page 7] RFC 2546 6Bone Routing Practice March 1999

10. Security Considerations

   The result of bogus entries in routing tables is usually
   unreachable sites.  Having guidelines to aggregate or reject routes
   will clean up the routing tables. It is expected that using these
   guidelines, routing on the 6Bone will be less sensitive to denial
   of service attacks due to misleading routes.
   The 6Bone is a test network. Therefore, denial of service, packet
   disclosure, are to be expected.

11. Acknowledgements

   This document is the result of shared experience on the 6Bone.
   Special thanks go to Bob Fink for the hard work make to date to
   direct the 6Bone effort, to David Kessens for the 6Bone registry,
   and to Guy Davies for his insightful contributions.

12. References

 [1]        Hinden, R. and S. Deering, "IP Version 6 Addressing
            Architecture", RFC 2373, July 1998.
 [RFC 2471] Hinden, R., Fink, R. and J. Postel (deceased), "IPv6
            Testing Address Allocation", RFC 2471, December 1998.
 [RFC 2080] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080,
            January 1997.
 [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
            Requirement  Levels", BCP 14, RFC 2119, March 1997.
 [RFC 2283] Bates, T., Chandra, R., Katz, D. and Y. Rekhter,
            "Multiprotocol Extensions for BGP-4", RFC 2283, March
 [RIPE-181] Bates, T., Gerich, E., Joncheray, L., Jouanigot, J.,
            Karrenberg, D., Terpstra, M. and J.  Yu,  Representation
            of IP Routing Policies in a Routing Registry.  Technical
            Report ripe-181, RIPE, RIPE NCC, Amsterdam, Netherlands,
            October 1994.

Durand & Buclin Informational [Page 8] RFC 2546 6Bone Routing Practice March 1999

13. Authors' Addresses

 Alain Durand
 Institut d'Informatique et de Mathematiques Appliquees de Grenoble
 38041 Grenoble CEDEX 9 France
 Phone : +33 4 76 63 57 03
 Fax   : +33 4 76 51 49 64
 Bertrand Buclin
 AT&T International S.A.
 Route de l'aeroport 31, CP 72
 CH-1215 Geneve 15 (Switzerland)
 Phone : +41 22 929 37 40
 Fax   : +41 22 929 39 84

Durand & Buclin Informational [Page 9] RFC 2546 6Bone Routing Practice March 1999

14. Full Copyright Statement

 Copyright (C) The Internet Society (1999).  All Rights Reserved.
 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
 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
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an

Durand & Buclin Informational [Page 10]

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