RFC 2928

Initial IPv6 Sub-TLA ID Assignments

📅 published September 2000, from ietf

RFC 2928: Initial IPv6 Sub-TLA ID Assignments ✨

okay bestie, let's get into RFC 2928 🦋 It's an Informational doc, so it's giving "here's some info for the community" and not a standard 💅 It's dated September 2000 and written by R. Hinden (Nokia), S. Deering (Cisco), R. Fink (LBNL) and T. Hain (Microsoft) 🎀 The title block doesn't list it as obsoleting or updating anything, so it stands on its own 🌸

Status of this Memo 💌

this memo gives info to the Internet community. it does NOT specify an Internet standard of any kind 🙈 and distribution is unlimited, so share it with your whole group chat 🫶

Copyright Notice ©

Abstract 🧚

okay so this doc defines the first batch of IPv6 Sub-TLA IDs (Sub-Top-Level Aggregation Identifiers) handed out to the Address Registries 💜 It's technical input to IANA from the IETF's IPNG and NGTRANS working groups, and it helps feed into the process of making guidelines for how IPv6 addresses get allocated 🍓

it was originally written to advise IANA back in the fall of 1998, and it's being published now for the historical record 📜 The IAB later asked IANA to hand these assignments off to the Address Registries. IANA did, and the Address Registries are now using them to assign IPv6 addresses ✨ iconic glow-up

1. Introduction ✨

so this is basically the same story as the abstract 💅 It was first written to advise IANA in fall 1998, it's being published now for the historical record, the IAB later asked IANA to delegate these assignments to the Address Registries, IANA did it, and the registries are using them to assign IPv6 addresses 🦋

the doc defines the initial assignments of IPv6 Sub-TLA Aggregation Identifiers (Sub-TLA IDs) to the Address Registries 🎀 It's technical input to IANA from the IETF IP Next Generation (IPNG) and Next Generation Transition (NGTRANS) working groups, and it feeds into the process of developing guidelines for allocating IPv6 addresses 🫶

the IAB and IESG authorized IANA as the right entity to manage the IPv6 address space, as defined in [ALLOC] 👑

the proposed initial assignment in this document is consistent with:

RFC 2373,"IP Version 6 Addressing Architecture" [ARCH]
RFC 2374 "An Aggregatable Global Unicast Address Format" [AGGR]
RFC 2450 "Proposed TLA and NLA Assignment Rules" [TLA-RULES]

2. Background 🌈

okay so [TLA-RULES] says TLA assignments happen in two stages 💖 Stage one is allocating a Sub-TLA ID, and this document is where the initial Sub-TLA ID assignments to the Registries get specified 🧚

here's how [TLA-RULES] Section 5.1 sets it up. Heads up, the diagram and the text are quoted straight from that spec 🙈

"Sub-TLA ID's are assigned out of TLA ID 0x0001 as follows. Note that use of the Reserved field to create the Sub-TLA field is specific to TLA ID 0x0001. It does not affect any other TLA.

| 3  |    13    |    13   |       19      |
+----+----------+---------+---------------+
| FP |   TLA    | Sub-TLA |       NLA     |
|    |   ID     |         |       ID      |
+----+----------+---------+---------------+

where: FP = 001 = Format Prefix This is the Format Prefix used to identify aggregatable global unicast addresses. TLA ID = 0x0001 = Top-Level Aggregation Identifier This is the TLA ID assigned by the IANA for Sub-TLA allocation. Sub-TLA ID = Sub-TLA Aggregation Identifier The Sub-TLA ID field is used by the registries for initial allocations to organizations meeting the requirements in Section 5.2 of this document. The IANA will assign small blocks (e.g., few hundred) of Sub-TLA ID's to registries. The registries will assign the Sub-TLA ID's to organizations meeting the requirements specified in Section 5.2. When the registries have assigned all of their Sub-TLA ID's they can request that the IANA give them another block. The blocks do not have to be contiguous. The IANA may also assign Sub-TLA ID's to organizations directly. This includes the temporary TLA assignment for testing and experimental usage for activities such as the 6bone or new approaches like exchanges. NLA ID = Next-Level Aggregation Identifier Next-Level Aggregation ID's are used by organizations assigned a TLA ID to create an addressing hierarchy and to identify sites. The organization can assign the top part of the NLA ID in a manner to create an addressing hierarchy appropriate to its network."

Note: In the above quote from [TLA-RULES] the references to "Section 5.2" refer to section 5.2 in [TLA-RULES]. 📎

3. Initial Assignments 💅

so, as [TLA-RULES] says, Sub-TLA ID assignments get made in blocks 🍓 The initial Sub-TLA ID assignments to IP address registries come in blocks of 64 Sub-TLA IDs, and here's the list 👇

Binary Value      IPv6 Prefix Range                 Assignment
----------------  -------------------------------   -------------------
0000 000X XXXX X  2001:0000::/29 - 2001:01F8::/29   IANA
0000 001X XXXX X  2001:0200::/29 - 2001:03F8::/29   APNIC
0000 010X XXXX X  2001:0400::/29 - 2001:05F8::/29   ARIN
0000 011X XXXX X  2001:0600::/29 - 2001:07F8::/29   RIPE NCC
0000 100X XXXX X  2001:0800::/29 - 2001:09F8::/29   (future assignment)
0000 101X XXXX X  2001:0A00::/29 - 2001:0BF8::/29   (future assignment)
0000 110X XXXX X  2001:0C00::/29 - 2001:0DF8::/29   (future assignment)
0000 111X XXXX X  2001:0E00::/29 - 2001:0FF8::/29   (future assignment)
0001 000X XXXX X  2001:1000::/29 - 2001:11F8::/29   (future assignment)
  .   .    .
  .   .    .
  .   .    .
1111 111X XXXX X  2001:FE00::/29 - 2001:FFF8::/29   (future assignment)

where "X" means "0" or "1" 🙈

any other Sub-TLA ID values not listed above are reserved 🔒

when a registry has used up all the Sub-TLA IDs in its block, it can ask IANA for another block 🫶 And the blocks given to a registry don't have to be contiguous. Okay, no cap, that's flexible.

the block assigned to IANA (2001:0000::/29 - 2001:01F8::/29) is for testing and experimental usage, to support things like the 6bone and new approaches like exchanges 🧪 that's the whole vibe of that block 🌸

4. Acknowledgments 💖

the authors want to thank Joyce K. Reynolds, Thomas Narten, Kim Hubbard, Mirjam Kuehne, and Brian Carpenter for helping out with this document 🥹

5. Security Considerations 🔐

okay listen up, this part matters 😭 IPv6 addressing documents do not have any direct impact on Internet infrastructure security. Authentication of IPv6 packets is defined in [AUTH]. Authentication of the ownership of prefixes to avoid "prefix stealing" is a related security issue but is beyond the scope of this document. 💀

6. References 📚

[AGGR] Hinden, R., Deering, S. and M. O'Dell, "An Aggregatable Global Unicast Address Format", RFC 2374, July 1998.
[ALLOC] IAB and IESG, "IPv6 Address Allocation Management", RFC 1881, December 1995.
[ARCH] Hinden, R., "IP Version 6 Addressing Architecture", RFC 2373, July 1998.
[AUTH] Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402, November 1998.
[IPV6] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998.
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996.
[TLA-RULES] Hinden, R., "Proposed TLA and NLA Assignment Rules", RFC 2450, December 1998.
[TST-ALLOC] Hinden, R., Fink R. and J. Postel, "IPv6 Testing Address Allocation", RFC 2471, December 1998.

7. Authors' Addresses 🏡

Robert M. Hinden
Nokia
313 Fairchild Drive
Mountain View, CA 94043
USA

Phone: +1 650 625-2004
EMail: hinden@iprg.nokia.com


Stephen E. Deering
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA

Phone: +1 408 527-8213
EMail: deering@cisco.com


Robert L. Fink
Lawrence Berkeley National Lab
1 Cyclotron Rd.
Bldg 50A, Room 3111
Berkeley, CA 94720
USA

Phone: +1 510 486-5692
EMail: rlfink@lbl.gov


Tony Hain
Microsoft

Phone: +1 425 703-6619
EMail: tonyhain@microsoft.com

8. Full Copyright Statement ⚖️

Copyright (C) The Internet Society (2000). 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 English. 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 "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.

Acknowledgement 🫶

funding for the RFC Editor function is currently provided by the Internet Society 💜 bestie, that's the whole doc, and it's a whole vibe ✨

📦 where this page comes from

ietf: rfc2928 2000-09
💖 girlified by claude-haiku-5-5 on 2026-10-16: a language model's rewrite of the original, under its terms