RFC3587 - IPv6 Global Unicast Address Format

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Network Working Group R. Hinden

Request for Comments: 3587 Nokia

Obsoletes: 2374 S. Deering

Category: Informational Cisco

E. Nordmark

Sun

August 2003

IPv6 Global Unicast Address Format

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 (2003). All Rights Reserved.

Abstract

This document obsoletes RFC2374, "An IPv6 Aggregatable Global

Unicast Address Format". It defined an IPv6 address allocation

strUCture that includes Top Level Aggregator (TLA) and Next Level

Aggregator (NLA). This document makes RFC2374 and the TLA/NLA

structure historic.

1. Introduction

RFC2374, "An IPv6 Aggregatable Global Unicast Address Format",

defined an IPv6 address allocation structure that includes TLA and

NLA. This document replaces RFC2374, and makes RFC2374 and the

TLA/NLA structure historic.

2. TLA/NLA Made Historic

The TLA/NLA scheme has been replaced by a coordinated allocation

policy defined by the Regional Internet Registries (RIRs) [IPV6RIR].

Part of the motivation for obsoleting the TLA/NLA structure is

technical; for instance, there is concern that TLA/NLA is not the

technically best approach at this stage of the deployment of IPv6.

Moreover, the allocation of IPv6 addresses is related to policy and

to the stewardship of the IP address space and routing table size,

which the RIRs have been managing for IPv4. It is likely that the

RIRs' policy will evolve as IPv6 deployment proceeds.

The IETF has provided technical input to the RIRs (for example,

[RFC3177]), which the RIRs have taken into account when defining

their address allocation policy.

RFC2374 was the definition of addresses for Format Prefix 001

(2000::/3) which is formally made historic by this document. Even

though currently only 2000::/3 is being delegated by the IANA,

implementations should not make any assumptions about 2000::/3 being

special. In the future, the IANA might be directed to delegate

currently unassigned portions of the IPv6 address space for the

purpose of Global Unicast as well.

The Subnet Local Aggregator (SLA) field in RFC2374 remains in

function but with a different name in [ARCH]. Its new name is

"subnet ID".

3. Address Format

The general format for IPv6 global unicast addresses as defined in

"IP Version 6 Addressing Architecture" [ARCH] is as follows:

n bits m bits 128-n-m bits

+-------------------------+-----------+----------------------------+

global routing prefix subnet ID interface ID

+-------------------------+-----------+----------------------------+

where the global routing prefix is a (typically

hierarchically-structured) value assigned to a site (a cluster of

subnets/links), the subnet ID is an identifier of a subnet within the

site, and the interface ID is as defined in section 2.5.1 of [ARCH].

The global routing prefix is designed to be structured hierarchically

by the RIRs and ISPs. The subnet field is designed to be structured

hierarchically by site administrators.

[ARCH] also requires that all unicast addresses, except those that

start with binary value 000, have Interface IDs that are 64 bits long

and to be constructed in Modified EUI-64 format. The format of

global unicast address in this case is:

n bits 64-n bits 64 bits

+-------------------------+-----------+----------------------------+

global routing prefix subnet ID interface ID

+-------------------------+-----------+----------------------------+

where the routing prefix is a value assigned to identify a site (a

cluster of subnets/links), the subnet ID is an identifier of a subnet

within the site, and the interface ID is a modified EUI-64 format as

defined in [ARCH].

An example of the resulting format of global unicast address under

the 2000::/3 prefix that is currently being delegated by the IANA and

consistent with the recommendations in RFC3177 is:

3 45 bits 16 bits 64 bits

+---+---------------------+-----------+----------------------------+

001global routing prefix subnet ID interface ID

+---+---------------------+-----------+----------------------------+

4. Acknowledgments

The authors would like to eXPress our thanks to Alain Durand, Brian

Carpenter, Fred Templin, Julian Sellers, Jun-ichiro Itojun Hagino,

Margaret Wasserman, Michel Py, Pekka Savola, Tatuya Jinmei, and

Thomas Narten for their review and constructive comments.

5. References

5.1. Normative References

[ARCH] Hinden, R. and S. Deering, "IP Version 6 Addressing

Architecture", RFC3513, April 2003.

[IPV6] Deering, S. and R. Hinden, "Internet Protocol, Version 6

(IPv6) Specification", RFC2460, December 1998.

5.2. Informative References

[IPV6RIR] APNIC, ARIN, RIPE NCC, "IPv6 Address Allocation and

Assignment Policy", Document ID: ripe-267,

http://www.ripe.net/ripe/docs/ipv6policy.Html, January 22,

2003.

[RFC3177] IAB/IESG, "Recommendations on IPv6 Address Allocations to

Sites", RFC3177, September 2001.

6. Security Considerations

IPv6 addressing documents do not have any direct impact on Internet

infrastructure security.

7. Authors' Addresses

Robert M. Hinden

Nokia

313 Fairchild Drive

Mountain View, CA

USA

EMail: bob.hinden@nokia.com

Stephen E. Deering

Cisco Systems, Inc.

170 West Tasman Drive

San Jose, CA 95134-1706

USA

Erik Nordmark

Sun Microsystems Laboratories

180, avenue de l'Europe

38334 SAINT ISMIER Cedex

France

EMail: erik.nordmark@sun.com

8. Full Copyright Statement

Copyright (C) The Internet Society (2003). 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 assignees.

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 RFCEditor function is currently provided by the

Internet Society.

 
 
 
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