On Aug 16, 2010, at 5:43 AM, Mark Smith wrote: > It seems to me that arguing against redirects is actually arguing for > having a common case, rather than an transient one, of nodes that don't > have full onlink prefix knowledge. I think having all nodes attached to > the link (i.e. both hosts and routers) being fully aware of all onlink > prefixes is a much better idea.
Not really, it's about the role of a device in a network. If there are multiple subnets within a single broadcast domain that require redirects to tell the hosts about what is on-link, it's much better to actually configure your host correctly (or have it actively participate vs passively via redirects) so they have knowledge of these additional subnets. If you're for random slop on a link, then redirects may be helpful, but that's not something that is architected well. I can't think of anyone that actually would PLAN for that type of environment. Most cases I've seen it involve into a mess over time. Preventing a mess and shifting the burden is what I'm speaking out about here. I've known many host guys who treat routers (and switches) as a "black box" that gets their packets/frames there. Sending them messages about alternate reachability of prefixes is useful in a trusted environment. Without authenticating those messages (ie: speaking in an active IGP) it can quickly become less useful noise and actually inhibit communication. All I've heard is that "someone might put two different subnets on the same broadcast domain and want helper messages to make a better decision" vs "redirects are REQUIRED to maintain reachability between end nodes". That is where I take issue with the tact being taken here. Requiring that a router send and hosts listen to these messages introduces complexities to the system. I can't get my vendors to produce stable router software in 2010, let alone expect the diverse business-units within the vendors to actually get this complexity right. Making something which I surely agree is a "nice to have" (due to latency reduction and other various intrinsic benefits) a requirement is shifting the burden and introducing complexity (to hosts and routers) where it's not necessary. Just because you can build it with "redirects" does not make it good or a desirable solution. - Jared -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
