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Re: Flow label and its uses

In the NIMROD scenario, the flow label identifies something akin to a virtual circuit; more properly, it identifies an aggregated route. A "map" (a bag of prefixes advertised by a network entity such as an ISP or an enterprise network) is connected to the network of reference by some route, and the flow label permits a high speed lookup, rather than looking up the prefix. It is very much like the MPLS label lookup done in MPLS routing. Sham's draft referenced earlier in the thread has a similar model.
RFC 3697 proposes that it be used for source classification of the traffic; the router is supposed to look up the flow label and use that in diffserv classification in a manner similar to the current use of the DSCP; the values an application could expect to find support for in the network would have to be installed in the path by some form of signaling or be well known in the network.
Either way, the forwarding implementation (whether software or firmware) is going to be looking up the flow label in the data path. Hence Bora's comment that it has to be aware of the flow label. 

On Jan 18, 2006, at 10:40 AM, Pekka Savola wrote:


Hi,

On Wed, 18 Jan 2006, Bora Akyol wrote:

From a switching hardware perspective, it would be nice
to either define the use of this field as --endpoint only--
or label it "Reserved."

There has been significant time since RFC3697 and the lack
of applications may indicate that this field (with
the exception of NIMROD) may not have a use at all.


I've been watching this discussion with mild puzzlement.
There is (basically) nothing that the routers need to do with the flow label. Whatever they might end up doing with it would likely mostly fall under the control plane, so it doesn't need to be put in the hardware.
So what's the problem? Do you want to try to reuse the "basically unused 20 bits" for some local purposes? That's not going to be allowed. 

--
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings