At 12:15 PM 12/13/01 -0800, David Meyer wrote:
>I didn't see any comment on this question. Did I miss it?
Nope. I have only just got to reading Vince's comments...
But I'll address them here...
>>> One question: is the next-generation routing system constrained to preserve
>>> the pure hop-by-hop forwarding model that we've all grown to know and love?
>>> I've read through section 3.9 of the draft so far between IETF sessions and
>>> don't see anything that states that thus far.
Section 3.27 explictly says we preserve the current HbH model,
but others _may_ be added. Yes, this does conflict with the "clean
sheet of paper" ideal, but it seems that we do want to make this
limitation. _Eliminating_ the HbH model seems to me to require that
we change too much stuff that is not directly related to routing.
>>> Why is this question relavent? Because it directly affects the set of
>>> policies that can be supported and how those policies are applied. On
>>> today's Internet, "policy" is primarily about setting the next hops that
>>> traffic uses when it exits a particular domain, with brute-force methods
>>> used to try and engineer end-to-end paths on a per-prefix granularity.
>>> But this isn't really what providers of edge or transit services really
>>> want; they want to be able to specify how traffic flows to the customers
>>> of their service - those who pay more should get better service. In today's
>>> world, the mapping between what the routing system can deliver and what
>>> the services that ride on top of that system would like to see don't match
>>> well at all, which is why horrible, non-scalable kludges such as more-
>>> specific route propagation are used in the name of "traffic engineering".
The current _tools_ for implementing "policy" are what
Vince describes. But we're not trying to require the current
tool set (if we do, we probably would end up with the current
system, but maybe with 48-bit AS numbers :-). We are trying
to figure out what it is that the operators are actually
trying to do and then say "the routing system must support
that" (at least, insofar as it is relevant).
But this is a very hard problem.
Frank Kastenholz
This archive was generated by hypermail 2b29 : Mon Aug 04 2003 - 04:10:03 EDT