One document matched: draft-xia-16ng-end-01.txt
Differences from draft-xia-16ng-end-00.txt
Network Working Group F. Xia
Internet-Draft B. Sarikaya
Intended status: Standards Track Huawei USA
Expires: June 4, 2007 Dec 2006
Duplicate Address Detection Optimization Using Enhanced Neighbor
Discovery
draft-xia-16ng-end-01
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2006).
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Abstract
This draft describes a possible optimization to Duplicate Address
Detection (DAD) which can be used to successfully terminate DAD
early. The method is based on a positive RA message sent by an
Neighbor Discovery Relay Agent that knows all the IPv6 addresses of
the nodes currently attached to it.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Scenario of Enhanced Neighbor Discovery . . . . . . . . . . . 4
3.1. Address cache . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Enhanced Relay DAD procedure . . . . . . . . . . . . . . . 4
3.3. Available Address option . . . . . . . . . . . . . . . . . 5
3.4. Timing Analysis . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Normative References . . . . . . . . . . . . . . . . . . . 8
5.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Introduction
IPv6 nodes can statelessly auto configure their own IP addresses on a
network, based on the information sent by the IPv6 router of that
network. When a node wishes to create a new address on an interface,
it combines the network prefix obtained from the router with a suffix
generated from its 64-bit Interface Identifier. This new untested
address is referred to as a Tentative Address (TA). The node joins
the appropriate solicited-node multicast group for this address, then
sends a Neighbor Solicitation (NS) message containing the TA. If the
TA is already in use by another node, that node will reply with a
Neighbor Advertisement (NA) defending the TA.
Once it has sent the NS, the node waits for RetransTimer [DISCOVERY]
milliseconds to see if a defending NA is forthcoming, and this
solicit-and-wait process is repeated DupAddrDetectTransmits
[DISCOVERY] times. The default value of RetransTimer is 1000ms and
by default the process is only done once, resulting a delay of 1000ms
or 1s.
This procedure provides a reasonable approach to checking address
uniqueness in situations such as fixed installation, or even mobile
web-browsing where 1s is not a significant delay. However, it is not
tolerable for some time-critical mobile applications like Voice Over
IP (VoIP).
2. Terminology
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 [STANDARDS].
SS - Subscriber Station (SS)
ND Relay Agent - A function entity which all SSs attach to. It
maintains authoritative information about SSs' IPv6 addresses.
END - Enhanced Neighbor Discovery
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3. Scenario of Enhanced Neighbor Discovery
In WiMAX architecture, A Bridge function entity is introduced in the
Ethernet CS environment as per [EthernetCS]. The bridge acts as a ND
Relay Agent. The ND Relay Agent knows all the IPv6 addresses of the
nodes currently attached to it.
3.1. Address cache
Address Cache is a conceptual data structure managed by an ND Relay
Agent that contains a list of addresses that are being used by the
SSs. The cache is authoritative, and how to maintain it is beyond
the scope of this memo.
3.2. Enhanced Relay DAD procedure
+-------+ +---------------+ +-------+
| SS1 | | ND Relay Agent| | SS2 |
+-------+ +---------------+ +-------+
| | |
|IPv6 Address | |
|Construction | |
(1) |------+ | |
| | | |
|<-----+ | |
| | |
| MLD Join | |
(2) |---------------------->| |
| | |
| DAD NS | |
(3) |---------------------->| |
| |Addr. Cache Lookup |
(4) | |------+ |
| | | |
| |<-----+ |
| RA | |
(5) |<----------------------| |
| | |
| | DAD NS |
(6) | |---------------------->|
| | |
| DAD NA | |
(7) |<----------------------|<----------------------|
| | |
| | |
Figure 1: Enhanced Relay DAD
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1. SS1 constructs an IPv6 Address. The address can be created as
per [ADDRCONF], or other alternatives.
2. SS1 constructs a solicited node multicast address for the
corresponding IPv6 Address and sends MLD Join request for the
solicited node multicast address.
3. SS1 starts verifying address uniqueness by sending a DAD NS.
4. ND Relay Agent looks into the authoritative address cache to
check if the address is already in use. If the address is not in
use then step 5, else step 6.
5. The ND Relay Agent sends a RA with an Available Address option to
indicate the uniqueness of the detected address. The detail
information about the new option is described later. On
receiving the positive RA, SS1 uses the address right now and
stops the DAD procedure.
6. ND Relay Agent relays the DAD NS to the address owner (SS2) in
case there is match in the address cache.
7. SS2 defends the address by sending DAD NA, which is relayed to
SS1 via the ND Relay Agent. Upon on receiving the DAD NA, it
discards the tentative address and behaves as specified in
[ADDRCONF]
3.3. Available Address option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |P| Reserved1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Available Address option
Fields:
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Type: TBD.
Length: 3, in units of 8 octets.
P: 1 bit. When set, indicates the uniqueness of IPv6 address carried
in the option. When not set, the option should be ignored.
Reserved1: 15-bit unused field. It MUST be initialized to zero by
the sender and MUST be ignored by the receiver.
Reserved2: 32-bit unused field. It MUST be initialized to zero by
the sender and MUST be ignored by the receiver.
IPv6 Address: Available IPv6 address.
3.4. Timing Analysis
In normal DAD, the process defined in [DISCOVERY] and [ADDRCONF],
takes DupAddrDetectTransmits*RetransTimer before the SS can start
using the address. In Optimistic DAD process [OPTDAD], as soon as an
address is configured on an interface, the address can be used. That
is, it takes 0 ms to use a tentative address with the risk of address
collision.
In case of END described in this memo, it takes a NS and RA round
trip time so that an address can be determined unique in most cases.
The round trip duration is much less than
DupAddrDetectTransmits*RetransTimer.
If END and [OPTDAD] are enabled, the SS will benefit from both the
reliability and time advantages.
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4. Security Considerations
There are existing security concerns with Neighbor Discovery and
Stateless Address Auto configuration. Secure Neighbor Discovery
(SEND) [SEND] provides protection against the threats to Neighbor
Discovery described in [NDTM]. This memo does not introduce any
additional threats to Neighbor Discovery.
In Relay DAD, ND Relay Agents relay NS and NA between SSs without
modifying any contents of messages. The target address in Neighbor
Advertisement and in solicited Router Advertisement is equal to the
source address of the packet.
SS can use CGAs for it's own address as defined [SEND]. SS can also
use Authorization Delegation Discovery [SEND] to find an authorized
ND Relay Agent.
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5. References
5.1. Normative References
[ADDRCONF]
Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998,
<ftp://ftp.isi.edu/in-notes/rfc2462>.
[DISCOVERY]
Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461,
December 1998, <ftp://ftp.isi.edu/in-notes/rfc2461>.
[MLD] Vida, R., Costa, L., and B. Haberman, "Multicast Listener
Discovery for IPv6", RFC 3810, June 2004,
<ftp://ftp.isi.edu/in-notes/rfc3810>.
[NDTM] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor
Discovery (ND) Trust Models and Threats", RFC 3756,
May 2004, <ftp://ftp.isi.edu/in-notes/rfc3756 >.
[OPTDAD] Moore, N., "Optimistic Duplicate Address Detection (DAD)
for IPv6", RFC 4429, April 2006,
<ftp://ftp.isi.edu/in-notes/rfc4429>.
[PESAA] Narten, T. and R. Draves, "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC 3041,
January 2001, <ftp://ftp.isi.edu/in-notes/rfc3041>.
[SEND] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "Secure
Neighbor Discovery (SEND)", RFC 3971, March 2005,
<ftp://ftp.isi.edu/in-notes/rfc3971>.
[STANDARDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997,
<ftp://ftp.isi.edu/in-notes/rfc2119>.
5.2. Informative References
[EthernetCS]
Jeon, H., Riegel, M., and S. Jeong, "Transmission of IP
Packets over Ethernet over IEEE 802.16", Oct 2006, <http:/
/www.watersprings.org/pub/id/
draft-riegel-16ng-ip-over-eth-over-80216-01.txt(work in
progress)>.
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Authors' Addresses
Frank Xia
Huawei USA
1700 Alma Dr. Suite 100
Plano, TX 75075
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
Behcet Sarikaya
Huawei USA
1700 Alma Dr. Suite 100
Plano, TX 75075
Phone: +1 972-509-5599
Email: sarikaya@ieee.org
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