[Docs] [txt|pdf|xml] [Tracker] [Email] [Diff1] [Diff2] [Nits]
Versions: 00 01 02
Network Working Group F. Templin, Ed.
Internet-Draft The Boeing Company
Intended status: Standards Track November 23, 2020
Expires: May 27, 2021
The IPv6 Link-Local Address Type Field
draft-templin-6man-lla-type-01
Abstract
IPv6 link-local addresses are formed from the prefix fe80::/10 which
is followed by 54 "zero" bits, then followed by a 64-bit Interface
Identifier. There are multiple methods for generating link-local
addresses, and multiple may be in use by nodes on the same link (and
sometimes even the same interface) at the same time. This document
defines an IPv6 link-local address "Type" field that identifies the
type of link-local address being used.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 27, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Templin Expires May 27, 2021 [Page 1]
Internet-Draft IPv6 Link-Local Address Type Field November 2020
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The IPv6 Link-Local Address Type Field . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The IPv6 link-local address prefix is defined in [RFC4291] as the
prefix fe80::/10 followed by 54 "zero" bits, then followed by a
64-bit interface identifier. There are multiple methods for
generating link-local addresses, and multiple may be in use on the
same link (and sometimes even the same interface) at the same time.
For example, [I-D.ietf-6man-rfc4941bis], [RFC7217], [RFC4291],
[RFC3972], [I-D.templin-6man-omni-interface] and possibly others
define diverse methods for generating interface identifiers for
constructing link-local addresses on a given interface.
Administrative configuration (e.g., manually setting the interface
ID) is also an option available to all interfaces.
IPv6 multi-addressing allows each interface to assign multiple IPv6
addresses, and even multiple IPv6 link-local addresses. On some
interfaces, it may even be the case that multiple link-local
addresses of different types would be configured at the same time.
But, since the diverse methods for generating interface identifiers
are not coordinated with one another, some interfaces may need a way
to differentiate the types of link-local addresses as well as to
avoid collisions and duplication.
This document defines a Type field in the link-local address prefix
for differentiating link-local address construction types. The Type
field also has a companion Function field which can be used to
perform Type-specific functions such as Prefix Delegation (PD).
This document updates [RFC4291].
Templin Expires May 27, 2021 [Page 2]
Internet-Draft IPv6 Link-Local Address Type Field November 2020
2. Terminology
The terminology in the normative references applies.
3. The IPv6 Link-Local Address Type Field
[RFC4291] defines the IPv6 link-local address format as the prefix
fe80::/10, followed by 54 zero bits, then followed by a 64-bit
Interface Identifier as shown in Figure 1:
| 10 |
| bits | 54 bits | 64 bits |
+----------+-------------------------+----------------------------+
|1111111010| 0 | interface ID |
+----------+-------------------------+----------------------------+
Figure 1: IPv6 Link-Local Address Format
In this format, there is currently no use for the 54 bits of 0s, and
existing IPv6-over-(foo) documents such as [RFC2464] expect them
always to be zero regardless of the method used in generating the
Interface ID.
However, new IPv6-over-(foo) documents could benefit from having a
coded indication of the link-local address construction type. This
would not only allow the interface to differentiate between the
address construction methods used by the sender in packets received
with link-local addresses, but it would also provide a means for
avoiding address duplication between diverse address
autoconfiguration methods used on the same link.
This document defines a new Type field in the IPv6 link-local address
prefix. The Type field and a companion Function field occupy the
least significant 16 bits of the 64-bit link-local address prefix as
shown in Figure 2:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|1|1|1|1|1|1|0|1|0| zeros (22 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| zeros (16 bits) | Function | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IPv6 Link-Local Prefix with Type Field
In this format, Type is an 8-bit field that identifies the link-local
address type on IPv6-over-(foo) interfaces that recognize the field,
Templin Expires May 27, 2021 [Page 3]
Internet-Draft IPv6 Link-Local Address Type Field November 2020
and Function is an 8-bit Type-specific field. The Type and Function
fields are present only when preceded by the prefix fe80::/48, and
are not present when preceded by any other prefix. The values for
Type that are currently defined are:
Link-Local Format Type
***************** ****
Unspecified (default) 0
Administratively Configured 1
RFC4941bis 2
RFC7217 3
RFC4291 4
RFC3972 5
OMNI 6
Figure 3
For example, on IPv6-over-(foo) interface types that recognize the
Type field, an IPv6 link-local address formed according to [RFC7217]
would be written as: fe80:0:0:3::[Interface ID], while one formed
according to [RFC3972] would be written as: fe80:0:0:5::[Interface
ID]. For some link types, it is possible that multiple types would
be assigned on the same link and possibly even on the same interface.
For Types '2' (RFC4941bis) and '6' (OMNI), PD clients set the
Function field to a non-zero prefix length value between 1 and 64 in
the source addresses of messages used to request a PD. For 'Type 6'
(OMNI), PD servers set the Function field to a non-zero prefix length
value between 1 and 64 in the destination addresses of messages used
to deliver a PD. For all other cases, the Function field is set to
the value 0 unless otherwise specified in a new link-local address
format specification, or in an update to this document.
Note that for existing IPv6-over-(foo) link types, the Type and
Function fields are always set to the value 0 (unspecified) and the
link local address format fe80::/64 still applies as it always has.
4. IANA Considerations
This document defines a Type field for IPv6 link-local addresses, for
which IANA is instructed to create and maintain a new registry
entitled "IPv6 Link-Local Address Type values". Initial values are
given below; future assignments are to be made through Expert Review
[RFC8126]:
Templin Expires May 27, 2021 [Page 4]
Internet-Draft IPv6 Link-Local Address Type Field November 2020
Link-Local Format Type
***************** ****
Unspecified (default) 0
Administratively Configured 1
RFC4941bis 2
RFC7217 3
RFC4291 4
RFC3972 5
OMNI 6
Figure 4: IANA IPv6 Link-Local Address Type Registry
5. Security Considerations
Security considerations for IPv6 [RFC8200] apply.
6. Acknowledgements
This document is aligned with the IETF 6man (IPv6) working group.
.
7. References
7.1. Normative References
[I-D.ietf-6man-rfc4941bis]
Gont, F., Krishnan, S., Narten, T., and R. Draves,
"Temporary Address Extensions for Stateless Address
Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12
(work in progress), November 2020.
[I-D.templin-6man-omni-interface]
Templin, F. and T. Whyman, "Transmission of IP Packets
over Overlay Multilink Network (OMNI) Interfaces", draft-
templin-6man-omni-interface-50 (work in progress), October
2020.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
Templin Expires May 27, 2021 [Page 5]
Internet-Draft IPv6 Link-Local Address Type Field November 2020
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217,
DOI 10.17487/RFC7217, April 2014,
<https://www.rfc-editor.org/info/rfc7217>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
7.2. Informative References
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<https://www.rfc-editor.org/info/rfc2464>.
Author's Address
Fred L. Templin (editor)
The Boeing Company
P.O. Box 3707
Seattle, WA 98124
USA
Email: fltemplin@acm.org
Templin Expires May 27, 2021 [Page 6]
Html markup produced by rfcmarkup 1.129d, available from
https://tools.ietf.org/tools/rfcmarkup/