Rationale for Update to the IPv6 Flow Label Specification
RFC 6436
Document | Type | RFC - Informational (November 2011; No errata) | |
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Authors | Sheng Jiang , Shane Amante , Brian Carpenter | ||
Last updated | 2015-10-14 | ||
Replaces | draft-carpenter-6man-flow-update | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 6436 (Informational) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Jari Arkko | ||
IESG note | Brian Haberman (brian@innovationslab.net) is the document shepherd for this document. | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) S. Amante Request for Comments: 6436 Level 3 Category: Informational B. Carpenter ISSN: 2070-1721 Univ. of Auckland S. Jiang Huawei November 2011 Rationale for Update to the IPv6 Flow Label Specification Abstract Various published proposals for use of the IPv6 flow label are incompatible with its original specification in RFC 3697. Furthermore, very little practical use is made of the flow label, partly due to some uncertainties about the correct interpretation of the specification. This document discusses and motivates changes to the specification in order to clarify it and to introduce some additional flexibility. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. 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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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/rfc6436. Amante, et al. Informational [Page 1] RFC 6436 Flow Label Update November 2011 Copyright Notice Copyright (c) 2011 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 (http://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 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Impact of Current Specification . . . . . . . . . . . . . . . 3 3. Changes to the Specification . . . . . . . . . . . . . . . . . 6 4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 7. Informative References . . . . . . . . . . . . . . . . . . . . 10 Appendix A. Alternative Approaches . . . . . . . . . . . . . . . 12 1. Introduction The flow label field in the IPv6 header was reserved but left Experimental by [RFC2460], which mandates only that "Hosts or routers that do not support the functions of the Flow Label field are required to set the field to zero when originating a packet, pass the field on unchanged when forwarding a packet, and ignore the field when receiving a packet." The flow label field was normatively specified by [RFC3697]. In particular, we quote three rules from that RFC: a. "The Flow Label value set by the source MUST be delivered unchanged to the destination node(s)." b. "IPv6 nodes MUST NOT assume any mathematical or other properties of the Flow Label values assigned by source nodes." c. "Router performance SHOULD NOT be dependent on the distribution of the Flow Label values. Especially, the Flow Label bits alone make poor material for a hash key." Amante, et al. Informational [Page 2] RFC 6436 Flow Label Update November 2011 Additionally, RFC 3697 does not define the method a host should adopt by default to choose the value of the flow label, if no specific method is in use. It was expected that various signaling methods might be defined for agreeing on values of the flow label, but no such methods have been standardized, except a pre-existing option in RSVP [RFC2205]. The flow label is hardly used in practice in widespread IPv6 implementations, although some operating systems do set it [McGann05]. To some extent, this is due to the main focus being on basic deployment of IPv6, but the absence of a default method of choosing the flow label value means that most host implementations simply set it to zero. There is also anecdotal evidence that theShow full document text