I have major, fundamental objection to the premises on which this draft is based on. However, I think we should be able to find consensus on the way forward.
Fundamental objection --------------------- The document assumes that it is always desirable to do load-sharing with the equivalent routers. I don't agree with this assumption. If the router's capacity is sufficient so that it can forward all the traffic sent by its nodes, there is actually very little need for load sharing. On the contrary -- sharing load between routers produces difficult-to-debug scenarios when some destinations (which are distributed to some routers) fail in mysterious ways while others work just fine. Due to that, I, as an operator, would not wish to enable load-sharing on hosts except when I specifically require that kind of functionality. So, I'd propose that this document does not describe that the hosts MUST share the load, but rather describes how the hosts MUST behave if they wish to share the load -- and if turned on by default, require that there MUST be a way to toggle load balancing off. A difficult issue to settle might be whether to recommend (and if so, how strongly) to enable load-sharing by default. substantial ----------- [ND] does not require any particular behavior in this respect. It specifies that an implementation may always choose the same router (e.g., the first in the list) or may cycle through the routers in a round-robin manner. Both of these suggestions are problematic. Clearly, always choosing the same router does not provide load sharing. Some problems with naive tie-breaking techniques such as round-robin and random are discussed in [MULTIPATH]. While the destination cache provides some stability since the determination is not per-packet, cache evictions or timeouts can still result in unstable or unpredictable paths over time, lowering the performance and making it harder to diagnose problems. Round- robin selection may also result in synchronization issues among hosts, where in the worst case the load is concentrated on one router at a time. ==> I don't think this document clearly described both of the above suggestion (1st paragraph): but rather how round-robin and random have issues. That is, it does not cleatly describe why choosing the same router is undesirable. As mentioned in [MULTIPATH], when next-hop selection is predictable, an application can synthesize traffic that will all hash the same, making it possible to launch a denial-of-service attack against the load sharing algorithm, and overload a particular router. A special case of this is when the same (single) next-hop is always selected, such as in the algorithm allowed by [ND]. Introducing hashing can make such an attack more difficult; the more unpredictable the hash is, the harder it becomes to conduct a denial-of-service attack against any single router. ==> these threats appear to have no clear threat model. What's the point of such an attack, as you're already on-link, and can already DoS the routers there using a number of means? Introducing hashing doesn't help much here -- you're making an assumption that the attacker is a "friendly" node. A maliscious node will just a) send the packets through raw sockets, DoSing the routers directly, or b) overload both of the routers :). It seems the security considerations needs a rewrite... editorial --------- ==> all the empty lines in the document appear to have been duplicated for some reason. Abstract The original IPv6 conceptual sending algorithm does not require load-sharing among equivalent IPv6 routers, and suggests schemes ==> s/IPv6/IPv6 Neighbor Discovery/ Subsequent traffic to the same destination address continues to use the same router unless there is some reason to change to a different router (e.g., a redirect message is received, or a router is found to be unreachable). ==> s/a router/the router/ 9. Full Copyright Statement ==> IPR boilerplate prior to this document would not hurt. -- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings -------------------------------------------------------------------- IETF IPv6 working group mailing list [EMAIL PROTECTED] Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
