On Tue, Aug 07, 2001 at 06:55:09PM -0400, Craig Partridge apparently wrote:
There are three separate issues (at least) here, so let's tease them out:
* Current routing protocols don't do policy. Very right and a known defect in IP routing (though in part, they don't do it because in the general case, policy is hard)
And policy-based routing everywhere is not scalable. OK, we could argue about the future, but I suspect that no matter how much power we give router owners, they'll come up with policies that use it all.
* Per hop policy decisions can be made more effectively in MPLS than in IP. Not true in theory unless you want to look very deep in the packet to identify the policy association, though it may be true in practice on certain current systems.
MPLS doesn't require per-hop policy decisions. Policy decisions only need to be made at the edge, re FEC inclusion. Intelligence at the edge etc. Parallels with the diffserv model of classifying & marking packets at the edge so you only need to look at PHBs in the middle.
* Instantiation of per-hop policy information via MPLS is more scalable than it would be in IP (not quite said above but an implied issue). Almost certainly not true (see above about general policy being hard being why IP doesn't do it).
Instantiation of per-hop policy in MPLS consists of forwarding by LSP, except at the edge router. ..Scott (at the IETF)