6BONE pTLA and pNLA Formats (pTLA)
RFC 2921

Document Type RFC - Informational (September 2000; No errata)
Last updated 2013-03-02
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Network Working Group                                            B. Fink
Request for Comments: 2921                                         ESnet
Category: Informational                                   September 2000

                   6BONE pTLA and pNLA Formats (pTLA)

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 (2000).  All Rights Reserved.

Abstract

   This memo defines how the 6bone uses the 3FFE::/16 IPv6 address
   prefix, allocated in RFC 2471, "IPv6 Testing Address Allocation",
   [6BONE-TLA], to create pseudo Top-Level Aggregation Identifiers
   (pTLA's) and pseudo Next-Level Aggregation Identifiers (pNLA's).

Acknowledgements

   The address formats here are contributions of various early
   participants of the 6bone testbed project, and of the IPng and
   NGtrans IETF working groups.

Table of Contents

   1.  Introduction................................................. 1
   2.  6BONE pTLA/pNLA Format....................................... 2
   3.  Security Considerations...................................... 6
   References....................................................... 6
   Author's Address................................................. 6
   Full Copyright Statement......................................... 7

1. Introduction

   This memo defines how the 6bone uses the 3FFE::/16 IPv6 address
   prefix, allocated in RFC 2471 [6BONE-TLA], to create pseudo Top-Level
   Aggregation Identifiers (pTLA) and pseudo Next-Level Aggregation
   Identifiers (pNLA).

Fink                         Informational                      [Page 1]
RFC 2921              6BONE pTLA and pNLA Formats         September 2000

   The guiding specifications for IPv6 addressing relating to the 6bone
   prefix, and the pTLA and pNLA formats, are "IP Version 6 Addressing
   Architecture"  [ADDRARCH], and "An IPv6 Aggregatable Global Unicast
   Address Format" [AGGR].

   The purpose of creating pseudo TLA and NLA formats for the 6bone is
   to provide a prototype of the actual TLA and NLA formats as they
   might be used in production IPv6 networks. To do this economically,
   using only a minimum of real production IPv6 address space, a single
   TLA, 3FFE::/16, was reserved by the IANA (Internet Assigned Numbers
   Authority) for testing on the 6bone. Thus it was necessary to define
   a pretend-to-be, or pseudo, TLA and NLA structure to use under the
   3FFE::/16 prefix.

   Given the 48-bit length of the IPv6 Aggregatable Global Unicast
   Address external routing prefix (that contains the TLA and NLA
   identifiers), there is enough room to extend the TLA ID to contain a
   pTLA and shorten the NLA ID to become a pNLA. This document specifies
   this.

   In early 1999, it was decided to change the 6bone's pTLA format to
   allow greater expansion of the testbed network, thus accommodating
   more than the original 256 pTLA-s. Thus there are now two 6bone pTLA
   and pNLA formats. This document specifies this.

2. 6BONE pTLA and pNLA Formats

2.1 Original 8-bit pTLA and 24-bit pNLA Format

   The original pTLA and pNLA format was intended to accommodate 256
   pTLA-s, i.e., backbone networks carrying IPv6 transit traffic.

   The original TLA and NLA ID-s as specified in [AGGR] are as follows:

      | 3 |  13 |          32         |   16   |    64 bits      |
      +---+-----+---------------------+--------+-----------------+
      |001| TLA |       NLA ID        | SLA ID | Interface ID    |
      +---+-----+---------------------+--------+-----------------+

   The TLA value 1FFE was assigned to the 6bone, which when viewed with
   the 3-bit format prefix in prefix notation form is 3FFE::/16.

   The first 8-bits of the NLA ID space are assigned as the pTLA that
   defines the top level of aggregation (backbone) for the 6bone. This
   provides for 256 6bone backbone networks, or pTLA-s, and leaves a
   24-bit pNLA ID for each pTLA to assign as needed.

Fink                         Informational                      [Page 2]
RFC 2921              6BONE pTLA and pNLA Formats         September 2000

      |     16    |  8  |     24      |   16   |    64 bits      |
      +-+---------+-----+-------------+--------+-----------------+
      |  0x3FFE   |pTLA |     pNLA    | SLA ID | Interface ID    |
      +-+---------+-----+-------------+--------+-----------------+

   In prefix notation form the pTLA is 3FFE:nn00::/24, where nn is the
   pTLA assignment.

   The remaining NLA ID space can be used by each pTLA for their
   downward aggregated delegation:

      |  n  |      24-n bits     |   16   |    64 bits      |
      +-----+--------------------+--------+-----------------+
      |pNLA1|       Site         | SLA ID | Interface ID    |
      +-----+--------------------+--------+-----------------+
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