RE: hard questions: request routing

["Cain, Brad" <bcain@cereva.com>]

Oliver,

> Simple path vectors prevent loops in the steady state.

This is the case with all routing protocols... they work
great in the steady state... then there are route flaps there
is inconsistency and therefore transient loops.. the only way
to prevent this is to perform a diffusion algorithm (e.g. DUAL)

> 1. Path vectors do not prevent transient loops which can happen during
>    changes in the value of the chosen metric. This changes  have to
>    be visible to all RRS before we can guarantee that there are 
>    no transient loops. Since the updates of the metric will be
>    frequent the transient loops will be frequent. 

I agree that frequent updates make the problem worse with
path vectors although this would be a problem with any
routing protocol

> 2. Using a single metric. I was makeing the point that RRS 
> path length is
>    obviously the wrong metric and that I don't think we know THE
>    single metric we can all use to achieve the goals of CDI.

Again, agree that a single metric makes good decisions
hard if not impossible

-brad