Transmission and Processing of IPv6 Extension Headers
RFC 7045
Internet Engineering Task Force (IETF) B. Carpenter
Request for Comments: 7045 Univ. of Auckland
Updates: 2460, 2780 S. Jiang
Category: Standards Track Huawei Technologies Co., Ltd.
ISSN: 2070-1721 December 2013
Transmission and Processing of IPv6 Extension Headers
Abstract
Various IPv6 extension headers have been standardised since the IPv6
standard was first published. This document updates RFC 2460 to
clarify how intermediate nodes should deal with such extension
headers and with any that are defined in the future. It also
specifies how extension headers should be registered by IANA, with a
corresponding minor update to RFC 2780.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7045.
Copyright Notice
Copyright (c) 2013 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Carpenter & Jiang Standards Track [Page 1]
RFC 7045 IPv6 Extension Header Transmission December 2013
Table of Contents
1. Introduction and Problem Statement . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirement to Transmit Extension Headers . . . . . . . . . . 5
2.1. All Extension Headers . . . . . . . . . . . . . . . . . . 5
2.2. Hop-by-Hop Options . . . . . . . . . . . . . . . . . . . 6
3. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 8
1. Introduction and Problem Statement
In IPv6, an extension header is any header that follows the initial
40 bytes of the packet and precedes the upper-layer header (which
might be a transport header, an ICMPv6 header, or a notional "No Next
Header").
An initial set of IPv6 extension headers was defined by [RFC2460],
which also described how they should be handled by intermediate
nodes, with the exception of the Hop-by-Hop Options header:
...extension headers are not examined or processed by any node
along a packet's delivery path, until the packet reaches the node
(or each of the set of nodes, in the case of multicast) identified
in the Destination Address field of the IPv6 header.
This provision meant that forwarding nodes should be completely
transparent to extension headers. There was no provision for
forwarding nodes to modify them, remove them, insert them, or use
them to affect forwarding behaviour. Thus, new extension headers
could be introduced progressively and used only by hosts that have
been updated to create and interpret them [RFC6564]. The extension
header mechanism is an important part of the IPv6 architecture, and
several new extension headers have been standardised since RFC 2460
was published.
Today, IPv6 packets are not always forwarded by straightforward IP
routing based on their first 40 bytes. Some routers, and a variety
of intermediate nodes often referred to as middleboxes, such as
firewalls, load balancers, or packet classifiers, might inspect other
parts of each packet. Indeed, such middlebox functions are often
embedded in routers. However, experience has shown that as a result,
the network is not transparent to IPv6 extension headers. Contrary
to Section 4 of RFC 2460, middleboxes sometimes examine and process
Carpenter & Jiang Standards Track [Page 2]
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