Optimistic Duplicate Address Detection (DAD) for IPv6
RFC 4429
| Document | Type |
RFC - Proposed Standard
(April 2006; Errata)
Updated by RFC 7527
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4429 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Margaret Cullen | ||
| Send notices to | (None) | ||
Network Working Group N. Moore
Request for Comments: 4429 Monash University CTIE
Category: Standards Track April 2006
Optimistic Duplicate Address Detection (DAD) for IPv6
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 (2006).
Abstract
Optimistic Duplicate Address Detection is an interoperable
modification of the existing IPv6 Neighbor Discovery (RFC 2461) and
Stateless Address Autoconfiguration (RFC 2462) processes. The
intention is to minimize address configuration delays in the
successful case, to reduce disruption as far as possible in the
failure case, and to remain interoperable with unmodified hosts and
routers.
Moore Standards Track [Page 1]
RFC 4429 Optimistic DAD April 2006
Table of Contents
1. Introduction ....................................................3
1.1. Problem Statement ..........................................3
1.2. Definitions ................................................4
1.3. Address Types ..............................................4
1.4. Abbreviations ..............................................5
2. Optimistic DAD Behaviors ........................................6
2.1. Optimistic Addresses .......................................6
2.2. Avoiding Disruption ........................................6
2.3. Router Redirection .........................................7
2.4. Contacting the Router ......................................7
3. Modifications to RFC-Mandated Behavior ..........................8
3.1. General ....................................................8
3.2. Modifications to RFC 2461 Neighbor Discovery ...............8
3.3. Modifications to RFC 2462 Stateless Address
Autoconfiguration ..........................................9
4. Protocol Operation .............................................10
4.1. Simple Case ...............................................10
4.2. Collision Case ............................................10
4.3. Interoperation Cases ......................................11
4.4. Pathological Cases ........................................11
5. Security Considerations ........................................12
Appendix A. Probability of Collision ..............................13
A.1. The Birthday Paradox ......................................13
A.2. Individual Moving Nodes ...................................14
Normative References ..............................................15
Informative References ............................................15
Acknowledgements ..................................................16
Moore Standards Track [Page 2]
RFC 4429 Optimistic DAD April 2006
1. Introduction
Optimistic Duplicate Address Detection (DAD) is a modification of the
existing IPv6 Neighbor Discovery (ND) [RFC2461] and Stateless Address
Autoconfiguration (SLAAC) [RFC2462] processes. The intention is to
minimize address configuration delays in the successful case, and to
reduce disruption as far as possible in the failure case.
Optimistic DAD is a useful optimization because in most cases DAD is
far more likely to succeed than fail. This is discussed further in
Appendix A. Disruption is minimized by limiting nodes' participation
in Neighbor Discovery while their addresses are still Optimistic.
It is not the intention of this memo to improve the security,
reliability, or robustness of DAD beyond that of existing standards,
but merely to provide a method to make it faster.
1.1. Problem Statement
The existing IPv6 address configuration mechanisms provide adequate
collision detection mechanisms for the fixed hosts they were designed
for. However, a growing population of nodes need to maintain
continuous network access despite frequently changing their network
attachment. Optimizations to the DAD process are required to provide
these nodes with sufficiently fast address configuration.
An optimized DAD method needs to:
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