Internet DRAFT - draft-gont-6man-ipv6-universal-extension-header
draft-gont-6man-ipv6-universal-extension-header
IPv6 maintenance Working Group (6man) F. Gont
Internet-Draft SI6 Networks / UTN-FRH
Obsoletes: 6564 (if approved) W. Liu
Intended status: Standards Track Huawei Technologies
Expires: March 19, 2016 S. Krishnan
Ericsson
H. Pfeifer
Rohde & Schwarz
September 16, 2015
IPv6 Universal Extension Header
draft-gont-6man-ipv6-universal-extension-header-02
Abstract
In IPv6, optional internet-layer information is encoded in separate
headers that may be placed between the IPv6 header and the transport-
layer header. There are a small number of such extension headers
currently defined. This document describes the issues that can arise
when defining new extension headers and specifies a new IPv6
Extension Header - the Universal Extension Header - that overcomes
the aforementioned problem, while enabling the extensibility of IPv6.
Finally, this document formally obsoletes RFC 6564.
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
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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 March 19, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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. A Problem with RFC 6564 . . . . . . . . . . . . . . . . . . . 3
4. Implications . . . . . . . . . . . . . . . . . . . . . . . . 3
5. UEH Specification . . . . . . . . . . . . . . . . . . . . . . 4
6. Forbidding New IPv6 Extension Headers . . . . . . . . . . . . 5
7. Operation of the UEH . . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
12.1. Normative References . . . . . . . . . . . . . . . . . . 6
12.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
There has recently been a lot of work in the area of IPv6 Extension
Headers. Firstly, there has been research about the extent to which
IPv6 packets employing Extension Headers are dropped in the public
Internet [GONT-IEPG-Nov13] [GONT-IEPG-Mar14], and debate about the
motivation behind such policy [I-D.gont-v6ops-ipv6-ehs-packet-drops].
Secondly, there has been a fair share of work to improve some
technicalities of IPv6 Extension Headers (see e.g. [RFC7112]
[RFC7045]) in the hopes that they can be reliably used in the public
Internet.
A key challenge for IPv6 Extension Headers to be "deployable" in the
public Internet is that they should not impair any nodes's ability to
process the entire IPv6 header chain. One of the steps meant in that
direction has been the specification of a Uniform Format for IPv6
Extension Headers [RFC6564], which was meant to be employed by any
IPv6 Extension Headers that might be defined in the future, such that
middle-boxes can still process the entire IPv6 header chain if new
new extension headers were specified. However, a problem in the
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aforementioned specification prevents such uniform format from being
of use.
Section 3 discusses the aforementioned flaw in the Uniform Format for
Extension Headers specified in [RFC6564]. Section 4 explicitly
describes the implications of the aforementioned flaw. Section 5
specifies the new Universal Extension Header (UEH). Section 7
explains how new IPv6 extensions would be specified with the UEH.
Section 6 formally forbids the specification of new IPv6 Extension
Headers (with new Next Header values), and mandates that any new IPv6
extensions be conveyed/encoded in the UEH specified in this document.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. A Problem with RFC 6564
A key problem with the Uniform Format for IPv6 Extension Headers
[RFC6564] lies in that both IPv6 Extension Headers and Transport
Protocols share the same "Next Header" registry/namespace. Thus,
given an "unknown Next Header value", it is impossible to tell
whether the aforementioned value refers to an IPv6 Extension Header
that employs the aforementioned uniform format, or an "unknown"
upper-layer protocol (e.g. an "unknown" transport protocol). That
is, while [RFC6564] specifies the syntax for a Uniform Format for
IPv6 Extension Headers, it does not provide a mechanism for a node to
identify whether the aforementioned format is being employed in the
first place.
4. Implications
The current impossibility to parse an IPv6 header chain that includes
unknown Next Header values results in concrete implications for the
extensibility of the IPv6 protocol, and the deployability of new
transport protocols. Namely,
o New IPv6 extension headers cannot be incrementally deployed.
o New transport protocols cannot be incrementally deployed.
Since there is no way for a node to process IPv6 extension headers
that employ unknown next header values, an IPv6 host that receives a
packet that employs a new IPv6 extension header will not be able to
parse the IPv6 header chain past that unknown extension header, and
hence it will drop the aforementioned packet
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[I-D.gont-v6ops-ipv6-ehs-packet-drops]. In a similar way, a
middlebox that needs to process the transport-protocol header will be
faced with the dilemma of what to do with packets that employ unknown
Next Header values. Since they will not be able to parse the IPv6
header chain past the unknown Next Header, it is very likely that
they will drop such packets.
Unfortunately, since transport protocols share the same namespace as
IPv6 Extension Headers, new transport protocols will pose the same
challenge to middle-boxes, and hence they will be likely dropped in
the network.
We believe that the current situation has implications that are
generally overlooked, and that, whatever the outcome, it should be
the result of an explicit decision by our community, rather than
simply "omission".
5. UEH Specification
This document specifies a new IPv6 Extension Header: Universal
Extension Header. This Extension Header is identified by the value
[TBD] of [IANA-IP-PROTO]. The syntax of the Universal Extension
Header is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Subtype | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
. .
. Subtype Specific Data .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Next Header
8-bit selector. Identifies the type of header immediately
following the extension header. Uses the same values as the IPv4
Protocol field [IANA-IP-PROTO].
Hdr Ext Len
8-bit unsigned integer. Length of the extension header in 8-octet
units, not including the first 8 octets.
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Subtype
8-bit unsigned integer. Specifies the subtype for this extension
header. It uses a new namespace managed by IANA [IANA-UEH].
Subtype Specific Data
Variable length. Fields specific to this extension header/
Subtype.
The Universal Extension Header specified in this document MAY appear
multiple times in the same IPv6 packet.
6. Forbidding New IPv6 Extension Headers
Since the specification of any new IPv6 Extension Headers (i.e., with
new Next Header values) would hamper (among other things) the
incremental deployment of extensions and new transport protocols, and
basic operational practices suchas as the enforcement of simple ACLs,
new IPv6 Extension Headers MUST NOT be specified in any future
specifications. Any IPv6 extensions that would require a new IPv6
Extension Header MUST be implemented with the Universal Extension
Header specified in this document. This minimizes breakage in
intermediate nodes that need to parse the entire IPv6 header chain.
7. Operation of the UEH
This section describes the operation of the Universal Extension
Header.
The goal of the UEH is to provide a common syntax for all future IPv6
extensions. Any future extension headers will be encoded in a UEH,
and will be identified by a specific UEH Subtype assigned by IANA at
the time the corresponding specification is published. The UEH thus
provides the "common syntax" required to process "unrecognized
extensions", and the Subtype field identifies the specific extension
being encoded in the UEH. Any "future extension headers" would
actually be new Subtypes (assigned by IANA) of the UEH.
As a result, unrecognized Next Header values should be interpreted to
identify an upper-layer protocol, rather than an IPv6 extension
header.
8. IANA Considerations
IANA is requested to create a new registry to maintain the Universal
Extension Header Subtypes [IANA-UEH].
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9. Security Considerations
Enabling nodes to parse an entire IPv6 header chain even in the
presence of unrecognized extensions allows for security mechanisms to
be implemented and deployed.
10. Acknowledgements
The authors would like to thank [TBD] for providing valuable input on
earlier versions of this document.
11. Contributors
C.M. Heard identified the problems related with the Uniform Format
for IPv6 Extension Headers specified in [RFC6564], and participated
in the brainstorming that led to this document.
12. References
12.1. Normative References
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC6564] Krishnan, S., Woodyatt, J., Kline, E., Hoagland, J., and
M. Bhatia, "A Uniform Format for IPv6 Extension Headers",
RFC 6564, DOI 10.17487/RFC6564, April 2012,
<http://www.rfc-editor.org/info/rfc6564>.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045,
DOI 10.17487/RFC7045, December 2013,
<http://www.rfc-editor.org/info/rfc7045>.
12.2. Informative References
[RFC7112] Gont, F., Manral, V., and R. Bonica, "Implications of
Oversized IPv6 Header Chains", RFC 7112,
DOI 10.17487/RFC7112, January 2014,
<http://www.rfc-editor.org/info/rfc7112>.
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[I-D.gont-v6ops-ipv6-ehs-packet-drops]
Gont, F., Hilliard, N., Doering, G., LIU, S., and W.
Kumari, "Operational Implications of IPv6 Packets with
Extension Headers", draft-gont-v6ops-ipv6-ehs-packet-
drops-00 (work in progress), July 2015.
[GONT-IEPG-Nov13]
Gont, F., "Fragmentation and Extension Header Support in
the IPv6 Internet", IEPG 88, November 3, 2013. Vancouver,
BC, Canada, 2013, <http://www.iepg.org/2013-11-ietf88/
fgont-iepg-ietf88-ipv6-frag-and-eh.pdf>.
[GONT-IEPG-Mar14]
Gont, F. and T. Chown, "More results from measurements of
IPv6 Extension Header probing", IEPG 89, March 2, 2014.
London, U.K., 2014, <http://www.iepg.org/2014-03-02-
ietf89/fgont-iepg-ietf89-eh-update.pdf>.
[IANA-IP-PROTO]
Internet Assigned Numbers Authority, "Assigned Internet
Protocol Numbers", April 2011,
<http://www.iana.org/assignments/protocol-numbers/
protocol-numbers.xhtml>.
[IANA-UEH]
Internet Assigned Numbers Authority, "Universal Extension
Header Subtypes", 2014.
Authors' Addresses
Fernando Gont
SI6 Networks / UTN-FRH
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: fgont@si6networks.com
URI: http://www.si6networks.com
Will (Shucheng) Liu
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R. China
Email: liushucheng@huawei.com
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Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
Email: suresh.krishnan@ericsson.com
Hagen Paul Pfeifer
Rohde & Schwarz
Muehldorfstrasse 15
Munich 81671
Germany
Phone: +49 89 4129 15515
Email: hagen.pfeifer@rohde-schwarz.com
URI: http://www.rohde-schwarz.com/
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