Subject: RE: Higher level question about flow label

From: [email-masked]
Date: Wed, 29 Aug 2001 23:28:28 +0300

In hope of maybe clearing out some of the confusion:

Brian E Carpenter wrote:
> > I fail to understand how either would break if they simply intrepret the
> > flow label semantics as 'the source has identified this set of packtes
> > as related'. In either case there is an out-of-band mechansim to 
> > translate the value to a router task. 

This could include "behavior aggregate flows"?

> But in the diffserv case, which is stateless (no signalling, 
> no soft state)
> the only out-of-band mechanism that works is if the flow label has
> intrinsic semantics. The fact that the packet belongs to a class is
> useless information on its own; you need to know what that 
> class means,
> and that can only be conveyed by an encoded field, since there is no
> signalling or state.

A PHB-ID in the flow label is NOT the semantics, but a pointer to the
semantics. The actual semantics are found from the respective specification,
and since all the possible (future) PHB-ID pointed semantics cannot be
hard-coded into the router, they need to be delivered to the router by some
out-of-band mechanism. This out-of-band mechanism will indeed establish
state at the router, not source specific state, but behavior aggregate flow
specific state. One could even imagine establishing this state with an
end-to-end signaling mechanism, which would result in a kind of host-to-host
specific behavior aggregate flow (RFC 2460 App.A could be read this way
already). Could be useful for e.g. experimental use??

	Jarno
--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [email-masked]
--------------------------------------------------------------------

---

From: Brian E Carpenter <[email-masked]>
Date: Thu, 30 Aug 2001 16:08:27 -0500

[email-masked] wrote:
...
> out-of-band mechanism. 

Of course. Diffserv routers have to be configured by a QOS policy system.
See the POLICY, RAP and SNMPCONF WGs and the diffserv MIB and PIB.

> This out-of-band mechanism will indeed establish
> specific behavior aggregate flow 

That's what the bandwidth broker and SLS-signalling people are up to,
though none of that work is in the IETF yet.

   Brian