IPv6 Flow Label Specification
RFC 6437

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Internet Engineering Task Force (IETF)                         S. Amante
Request for Comments: 6437                                       Level 3
Obsoletes: 3697                                             B. Carpenter
Updates: 2205, 2460                                    Univ. of Auckland
Category: Standards Track                                       S. Jiang
ISSN: 2070-1721                                                   Huawei
                                                            J. Rajahalme
                                                  Nokia Siemens Networks
                                                           November 2011

                     IPv6 Flow Label Specification

Abstract

   This document specifies the IPv6 Flow Label field and the minimum
   requirements for IPv6 nodes labeling flows, IPv6 nodes forwarding
   labeled packets, and flow state establishment methods.  Even when
   mentioned as examples of possible uses of the flow labeling, more
   detailed requirements for specific use cases are out of the scope for
   this document.

   The usage of the Flow Label field enables efficient IPv6 flow
   classification based only on IPv6 main header fields in fixed
   positions.

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/rfc6437.

Amante, et al.               Standards Track                    [Page 1]
RFC 6437              IPv6 Flow Label Specification        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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  IPv6 Flow Label Specification  . . . . . . . . . . . . . . . .  4
   3.  Flow Labeling Requirements in the Stateless Scenario . . . . .  5
   4.  Flow State Establishment Requirements  . . . . . . . . . . . .  7
   5.  Essential Correction to RFC 2205 . . . . . . . . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
     6.1.  Covert Channel Risk  . . . . . . . . . . . . . . . . . . .  8
     6.2.  Theft and Denial of Service  . . . . . . . . . . . . . . .  8
     6.3.  IPsec and Tunneling Interactions . . . . . . . . . . . . . 10
     6.4.  Security Filtering Interactions  . . . . . . . . . . . . . 11
   7.  Differences from RFC 3697  . . . . . . . . . . . . . . . . . . 11
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Example 20-Bit Hash Function  . . . . . . . . . . . . 14

Amante, et al.               Standards Track                    [Page 2]
RFC 6437              IPv6 Flow Label Specification        November 2011

1.  Introduction

   From the viewpoint of the network layer, a flow is a sequence of
   packets sent from a particular source to a particular unicast,
   anycast, or multicast destination that a node desires to label as a
   flow.  From an upper-layer viewpoint, a flow could consist of all