RE: IP QoS issues

[Masataka Ohta <mohta at necom830.hpcl.titech.ac.jp>]

Karl;

> Yes, once we have stable routing, many difficulties will go away. 
> However, even within an autonomous area, as you suggest in your paper on
> QoS routing (with pinned routes), there are, in real-life nets, enough
> failures and other sources of instability to make betting on the
> permanence of routes rather like betting on a slow horse in a fast race. 

The failures in the Internet with QoS will be as infrequent as that
of telephone network today, with which, most, if not all, of the
people will be satisfied.

Another source of instability is existence of a better route
and see below.

> And once one gets out into the big-bad world of inter-ISP routing, the
> concern usually isn't whether routes flap, but how fast.

It depends on how much we underestimate the goodness of
alternative routes.

In an extreme case, we may ignore alernative route unless the
current route become unavailable.

> I suspect that you are going to say "route pinning will stop most
> flapping".

No. Route pinning won't work with multicast.

> If you were to say that, I'd answer "I'm not at all sure that
> inter-routing-domain pinning will be administratively acceptable to many
> operators and that I'm also skeptical that we have the technology to do
> that yet between routing domains."

That is, we should QoS-route hop-by-hop.

							Masataka Ohta