INTERNET-DRAFT R. Hinden/Nokia November 7, 2001 IPv6 Host to Router Load Sharing 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 Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." To view the list Internet-Draft Shadow Directories, see http://www.ietf.org/shadow.html. This internet draft expires on May 7, 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. draft-hinden-ipv6-host-load-sharing-00.txt [Page 1] INTERNET-DRAFT IPv6 Host to Router Load Sharing November 7, 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 fashion. 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. draft-hinden-ipv6-host-load-sharing-00.txt [Page 2] INTERNET-DRAFT IPv6 Host to Router Load Sharing November 7, 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. This should have the effect of distributing outgoing traffic for new destinations among the default routers. 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 MUST cycle through the router list in a round- robin fashion 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 also like to thank Erik Nordmark, Brian Haberman, Steve Deering, and Aron Silverton 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. [ND] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC2461, December 1998. draft-hinden-ipv6-host-load-sharing-00.txt [Page 3] INTERNET-DRAFT IPv6 Host to Router Load Sharing November 7, 2001 [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 draft-hinden-ipv6-host-load-sharing-00.txt [Page 4]