IPv6 Flow Label Specification
RFC 3697
Document | Type |
RFC - Proposed Standard
(March 2004; No errata)
Obsoleted by RFC 6437
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Authors | Brian Carpenter , Steve Deering , Jarno Rajahalme , Alex Conta | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 3697 (Proposed Standard) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Thomas Narten | ||
Send notices to | (None) |
Network Working Group J. Rajahalme Request for Comments: 3697 Nokia Category: Standards Track A. Conta Transwitch B. Carpenter IBM S. Deering Cisco March 2004 IPv6 Flow Label Specification Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document specifies the IPv6 Flow Label field and the minimum requirements for IPv6 source 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 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. 1. Introduction A flow is a sequence of packets sent from a particular source to a particular unicast, anycast, or multicast destination that the source desires to label as a flow. A flow could consist of all packets in a specific transport connection or a media stream. However, a flow is not necessarily 1:1 mapped to a transport connection. Rajahalme, et al. Standards Track [Page 1] RFC 3697 IPv6 Flow Label Specification March 2004 Traditionally, flow classifiers have been based on the 5-tuple of the source and destination addresses, ports, and the transport protocol type. However, some of these fields may be unavailable due to either fragmentation or encryption, or locating them past a chain of IPv6 option headers may be inefficient. Additionally, if classifiers depend only on IP layer headers, later introduction of alternative transport layer protocols will be easier. The usage of the 3-tuple of the Flow Label and the Source and Destination Address fields enables efficient IPv6 flow classification, where only IPv6 main header fields in fixed positions are used. The minimum level of IPv6 flow support consists of labeling the flows. IPv6 source nodes supporting the flow labeling MUST be able to label known flows (e.g., TCP connections, application streams), even if the node itself would not require any flow-specific treatment. Doing this enables load spreading and receiver oriented resource reservations, for example. Node requirements for flow labeling are given in section 3. Specific flow state establishment methods and the related service models are out of scope for this specification, but the generic requirements enabling co-existence of different methods in IPv6 nodes are set forth in section 4. The associated scaling characteristics (such as nodes involved in state establishment, amount of state maintained by them, and state growth function) will be specific to particular service models. 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 BCP 14, RFC 2119 [KEYWORDS]. 2. IPv6 Flow Label Specification The 20-bit Flow Label field in the IPv6 header [IPv6] is used by a source to label packets of a flow. A Flow Label of zero is used to indicate packets not part of any flow. Packet classifiers use the triplet of Flow Label, Source Address, and Destination Address fields to identify which flow a particular packet belongs to. Packets are processed in a flow-specific manner by the nodes that have been set up with flow-specific state. The nature of the specific treatment and the methods for the flow state establishment are out of scope for this specification. The Flow Label value set by the source MUST be delivered unchanged to the destination node(s). Rajahalme, et al. Standards Track [Page 2] RFC 3697 IPv6 Flow Label Specification March 2004 IPv6 nodes MUST NOT assume any mathematical or other properties of the Flow Label values assigned by source nodes. Router performanceShow full document text