Network Working Group S. Daniel Park
Internet-Draft SAMSUNG Electronics
Expires : January 2004 July 2003
Requirement for IPv6 DAD Optimization
<draft-park-ipv6-optidad-requirement-01.txt>
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Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document describes requirements how IPv6 DAD optimization should
be used for real time communications especially IPv6 mobility.
Conventions used in this document
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 RFC 2119 [2].
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Table of Contents
1. Introduction..................................................2
2. Intention / Scenario..........................................3
3. Requirements for IPv6 DAD Optimization........................3
3.1 Comparison with Original DAD.............................3
3.2 Neighbor Cache...........................................3
3.3 Host Modifications.......................................3
3.4 Router Modifications.....................................4
3.5 Security.................................................4
3.6 Address Duplication Considerations.......................4
3.7 Layer 2 Considerations...................................4
4. IANA Considerations...........................................4
5. Security Considerations.......................................5
6. References....................................................5
7. Author's Address..............................................5
8. Acknowledgements..............................................5
9. Intellectual Property Statement...............................5
10. Full Copyright Statement......................................6
1. Introduction
In order to generate unique address, an IPv6 node has to perform DAD
(Duplicate Address Detection) procedure when the IPv6 node tries to
make its own IPv6 address including link-local and global address.
However, a proper support for real time multimedia applications in
mobile environment is undermined by the disruption imposed by DAD.
Recently, some considerations are being suggested for DAD
optimization mechanisms to provide fast handover when a mobile node
is connected to the new networks. Real-time services require layer 3
handovers between IPv6 networks to be completed quickly and with
minimal packet loss. All IPv6 nodes must perform DAD every time they
handover between IPv6 networks. DAD described in [3] is a time
consuming process, particularly when nodes in need of seamless
handover run it. During DAD time, any active communications of nodes
are interrupted, and this is especially unsuitable for real-time
services.
This document clarifies the requirements for IPv6 DAD optimization at
the real time communications especially IPv6 mobility.
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2. Intention / Scenario
The intention is to minimize address configuration delays in the
successful case without greatly increasing disruption in the less
likely failure case. DAD optimization is a useful when a DAD is far
more likely to succeed than fail for randomly autoconfigured
addresses. This makes it worth a little disruption in the failure
case to provide faster handovers in the successful case, as long as
the disruption is easily recoverable.
Note that nodes which have DAD optimization functions SHOULD
interoperate with nodes which have original DAD functions.
3. Requirements for IPv6 DAD Optimization
The purpose of the DAD optimization mechanism is to provide
continuous real time communication like faster handovers in IPv6
mobility.
3.1 Comparison with Original DAD
When an original DAD is performed to verify address duplication,
there happened to be some delays (is defined in [3]) in this case. In
order to reduce delays, optimized DAD should be required to provide
faster handover in the IPv6 mobility. Though, at the same time, it
should be noted that the DAD optimization MUST NOT break the original
DAD mechanism.
3.2 Neighbor Cache
The Neighbor Cache entries MUST NOT be modified in a way which is
unrecoverable through original DAD operation [3]. For effective DAD
optimization, there are no restrictive requirements to modify
Neighbor Cache entry in the specific cases. Immediately on completing
the appropriate DAD procedure for either original DAD or DAD
optimization, all Neighbor?NC (Neighbor Cache) MUST be updated
appropriately.
3.3 Host Modifications
The DAD optimization SHOULD allow for the use of original DAD and NDP
(Neighbor Discovery Protocol) to a host even if a host wants to be
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modified for DAD optimization. For DAD optimization, a host including
neighbor MUST recognize modifications such as specific fields, flags,
values, etc.
3.4 Router Modifications
The DAD optimization SHOULD allow for the use of original DAD and NDP
to a router even if a router wants to be modified for DAD
optimization. For DAD optimization, a router MUST provide host
requirements.
3.5 Security
The DAD optimization scheme SHOULD NOT introduce any new attacks on
Neighbor Discovery and the resulting schemes should be no worse than
existing DAD [3]. There are existing security concerns with Neighbor
Discovery and Stateless Address Autoconfiguration. These schemes
SHOULD interoperate with Secure Neighbor DAD mechanisms as defined in
SEND WG.
3.6 Address Duplication Considerations
In the simplest collision case, the address being configured by the
new node is already in use by another node, and present in the
Neighbor Caches of neighbors which are communicating with this node.
At this case, all nodes MUST detect address duplication either
original DAD or DAD optimization.
3.7 Layer 2 Considerations
Generally, address duplication is happened to the same Interface ID
which is composed of 48bit/64bit MAC address. Therefore, when same
MAC address is existed in the same link, one of these nodes can not
make its IPv6 address using address autoconfiguration mechanism. At
this case, all nodes MUST be allowed to generate new addresses by
another mechanism. It should be clarified that the mechanisms should
be more discussed in the near future.
4. IANA Considerations
There are no IANA considerations in this document.
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5. Security Considerations
Section 3.5 specifies security requirements for DAD optimization.
6. References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Thomson, S., Narten, T., "IPv6 Stateless Address Autocon-
figuration" RFC 2462, December 1998.
[4] Narten, T. et. al., "Neighbor Discovery for IPv6" RFC 2461,
December 1998.
7. Author's Address
Soohong Daniel Park
Mobile Platform Laboratory, SAMSUNG Electronics
EMail: soohong.park@samsung.com
8. Acknowledgements
Specially thanks are due to Greg Delay for many useful comments.
9. Intellectual Property Statement
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