Internet DRAFT - draft-hinden-ipv6-host-load-sharing
draft-hinden-ipv6-host-load-sharing
INTERNET-DRAFT R. Hinden/Nokia
November 15, 2001
IPv6 Host to Router Load Sharing
<draft-hinden-ipv6-host-load-sharing-01.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC2026].
Internet-Drafts are working documents of the Internet Engineering
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This internet draft expires on May 15, 2002.
Abstract
This document defines a change to IPv6 Neighbor Discovery that IPv6
hosts can use to load share their outgoing traffic between multiple
default routers.
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INTERNET-DRAFT IPv6 Host to Router Load Sharing November 15, 2001
1. Introduction
IPv6 hosts on a LAN will usually learn about default routers by
receiving Router Advertisements sent using the IPv6 Neighbor
Discovery protocol [ND]. If there are multiple routers the hosts
will automatically learn about them and have multiple default routers
to send off link traffic.
IPv6 Neighbor Discovery protocol does not require any specific
procedure for hosts to divide (i.e., load share) outgoing traffic
between these routers. This document defines procedures that IPv6
hosts can use to load share their outgoing traffic between multiple
default routers.
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. Background
RFC2461 "Neighbor Discovery for IPv6" [ND] defines in section 6.3.6
an algorithm for selecting default routers. This algorithm is
invoked during next hop determination when no destination cache entry
exists for an off-link destination or when communication through an
existing router is failing. Normally a router would be selected the
first time traffic is sent to a specific destination. Subsequent
traffic to the same destination would continue to use this router
unless there was some other reason to change to a different router
(e.g., redirect message received, etc.).
ND further specifies that when there are multiple reachable default
routers, an implementation may always return the same router (e.g.,
the first in the list) or may cycle through the list of reachable
default routers in a round robin manner. It does not require any
specific behavior in the case of multiple default routers.
It is desirable when there is more than one default router that the
hosts distribute their outgoing traffic among these routers. This
document changes the ND behavior to require that an implementation
cycle through the list of default routers in a random order.
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INTERNET-DRAFT IPv6 Host to Router Load Sharing November 15, 2001
3. Load Sharing
The load sharing algorithm changes the currently specified default
router selection algorithm to cycle through the list of reachable
default routers in random order. This should have the effect of
distributing outgoing traffic for new destinations among the default
routers. Random selection, versus round robin, is used to avoid
synchronization in the hosts selection of a default router.
Bullet 1) in section 6.3.6 "Default Router Selection" [ND] is
replaced with the following:
1) Routers that are reachable or probably reachable (i.e., in any
state other than INCOMPLETE) SHOULD be preferred over routers
whose reachability is unknown or suspect (i.e., in the
INCOMPLETE state, or for which no Neighbor Cache entry exists).
An implementation SHOULD pick routers from the default router
list in random order while making sure it always returns a
reachable or a probably reachable router when one is available.
4. Acknowledgments
The author of this document would like to thank Erik Nordmark, Brian
Haberman, Steve Deering, Aron Silverton, and Christian Huitema for
their helpful suggestions.
5. Security Considerations
This document requires an node to cycle through a the list of default
routers. There are no known security issues with this change to IPv6
Neighbor Discovery.
6. References
[ADD-ARH] Hinden, R., S. Deering, "IP Version 6 Addressing
Architecture", RFC2373, July 1988.
[ICMPv6] Conta, A., S. Deering, "Internet Control Message Protocol
(ICMPv6) for the Internet Protocol Version 6 (IPv6)",
RFC2463, December 1998.
[IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC2460, December 1998.
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INTERNET-DRAFT IPv6 Host to Router Load Sharing November 15, 2001
[ND] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC2461, December 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC2119, BCP0014, March 1997.
7. Author's Address
Robert Hinden
Nokia
313 Fairchild Drive
Mountain View, CA 94043
US
Phone: +1 650 625-2004
Email: hinden@iprg.nokia.com
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