Margaret Wasserman wrote: > What is wrong with a hop-by-hop option? Isn't that the "right" > mechanism for an IPv6 host to send a "message" that is processed > by all routers in the path?
Hop-by-hop options will be slower to process, and the point is that the origin knows which packets belong together in any specific flow, and there is no way the routers can deduce that. If the origin specifies which packets belong together, there is no valid reason for anything along the path to decide otherwise. > >You are assuming that every router along the path is part of the same > >administrative system and would react consistently to the marking. > > No I'm not assuming that all routers in the path will understand > the flow label. I am assuming, though, that the flow label will > only be _useful_ within an administrative system that has > a consistent (or at least compatible) understanding of its meaning. I didn't state my argument clearly. I agree that not all routers along the path may care to pay attention, but as you said your assumption is that the ones that do are all are part of a single administrative system. This is not reasonable to assume in the general case, so what I am arguing is that routers in any independent administrative system in the path have consistent information to base decisions on. How they acquire the interpretation is independent of the fact that the bits are consistent throughout. > I don't understand how these three systems can usefully interpret > the same bits in two different ways. If I am choosing a random > flow label value at the source (with an "interactive system" that > indicates its meaning out-of-band), why won't I just get random > behaviour from the intermediate domain in your example? You might, but if we allow the intermediate domain to independently modify the bits there is no hope that the remote domain can get it right. As I said earlier, it is possible for the intermediate system to provide a predictable behavior based on the additional knowledge of FL without explicit knowledge of the semantics, but that might be more along the lines of drop-probability than EF or the like. > Then, why not leave the specification of flow label semantics and > rules to this same WG? Because the participants in those WGs have consistently proven they don't understand the concept of an architecturally consistent immutable field which the origin can trust. Tony -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
