Network Working Group F. Templin, Ed.
Internet-Draft Boeing Research & Technology
Intended status: Informational January 14, 2013
Expires: July 18, 2013
IPv6 Path MTU Updates
draft-generic-6man-tunfrag-07.txt
Abstract
IPv6 intentionally deprecates fragmentation by routers in the
network. Instead, links with restricting Maximum Transmission Units
(MTUs) must either drop each too-large packet and return an ICMPv6
Packet Too Big (PTB) message or perform link-specific fragmentation
and reassembly (also known as "link adaptation") at a layer below
IPv6. This latter category of links is often performance-challenged
to accommodate steady-state link adaptation. A common case that
exhibits these link characteristics is seen for IPv6-in-IP tunnels.
Additionally, IPv6 nodes can avoid path MTU discovery issues even
when no link adaptation is necessary by performing a small amount of
fragmentation and/or by probing the path as necessary. This document
therefore proposes an update to the base IPv6 specification to better
accommodate path MTU issues.
Status of this Memo
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Templin Expires July 18, 2013 [Page 1]
Internet-Draft IPv6 Path MTU Updates January 2013
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3
3. Considerations for Small MTU Paths . . . . . . . . . . . . . . 4
3.1. Accommodating Legacy Nodes . . . . . . . . . . . . . . . . 4
4. Considerations for Medium MTU Paths . . . . . . . . . . . . . . 5
5. Considerations for Large MTU Paths . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
Templin Expires July 18, 2013 [Page 2]
Internet-Draft IPv6 Path MTU Updates January 2013
1. Introduction
IPv6 intentionally deprecates fragmentation by routers in the
network. Instead, links with restricting Maximum Transmission Units
(MTUs) must either drop each too-large packet and return an ICMPv6
Packet Too Big (PTB) message or perform link-specific fragmentation
and reassembly (also known as "link adaptation") at a layer below
IPv6. This latter category of links is often performance-challenged
to accommodate steady-state link adaptation. A common case that
exhibits these link characteristics is seen for IPv6-in-IP tunnels
[I-D.generic-v6ops-tunmtu]. Additionally, IPv6 nodes can avoid path
MTU discovery issues even when no link adaptation is necessary by
performing a small amount of fragmentation and/or by probing the path
as necessary. This document therefore proposes an update to the base
datatracker.ietf.org