Subject: RE: refocusing: what about the flow label?

From: "Christian Huitema" <[email-masked]>
Date: Fri, 7 Sep 2001 08:44:19 -0700

> With the current flow label semantics the routers can avoid doing
> intserv
> state lookup if the flow label is null. If the flow label is used for
> path
> distribution, the router will be searching for the intserv state for
> all the
> packets (assuming the router does intserv at all). So from this
> point-of-view it might be better to designate a separate label type
> for
> intserv?

That should be a question for the Intserv WG. Either they can live with
the default mechanism, or they expand the effort of specifying their own
solution. I have no personal preference on this subject.

> What I'm aiming at is to see if a classifying router (intserv,
> diffserv, or other) could be ignorant of the different flow label 
> types when doing the lookup based on the 3-tuple of the source 
> address, destination address and the 20 bit flow label. 

That is indeed debatable. My proposal is to treat any non-understood
label as if it had been null; an alternate proposal could be to treat
any non-understood label as a basic label. Again, I don't have a strong
preference, we just need to pick one specification.

-- Christian Huitema

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From: Brian E Carpenter <[email-masked]>
Date: Fri, 07 Sep 2001 14:00:10 -0500

I believe Christian's proposal is quite viable. However I want to think a bit 
more about this, since there may actually be a solution much closer to
"no change" - I just don't feel quite ready to write it down yet, but I
suspect we can actually achieve the same effect without labels.

One more comment below:

> > address, destination address and the 20 bit flow label.

That depends quite critically on the extent to which the standard
limits the semantics of the field. A classifier is a dumb animal
driven by a simple configuration table; the real work is done
after classification. So there is a good chance this condition
can be met (with unrecognised labels reverting to default
treatment, as Christian says).

     Brian