[tsvwg] draft diffserv-intercon: Handling of a scavenger class / CS1

[<[e-mail]>]

Gorry,

the notes taken in Dallas (and thanks to the note taker!) showed a scavenger-class-at-interconnection related discussion.

Summary of Dallas discussion:
-       Scavenger is not supported at Interconnection, as CS1 is not a widely deployed standard DSCP for scavenger.
-       Taking this into account, there was a request for CS1 not to be re-marked to any other DSCP.

Basic questions:
-       Is the issue to get Scavenger support in a general DiffServ sense at Interconnection, i.e. the PHB is supported by the receiving domain but the DSCP may be remarked? To me, this would make Scavenger relevant for diffserv-intercon
-       Is the issue to avoid remarking of the DSCP, no matter whether the receiving domain supports Scavenger? As I agree to remove the remarking discussion from diffserv-intrcon, I'd regard this to be out of its scope (in both cases, if the receiving domain supports Scavenger by CS1 and also if it transports CS1 unchanged if it isn't aware of the DiffServ PHB indicated by it).

Those interested in scavenger class marked packets passing interconnection points are asked to respond.

My take:
-       The uniform model assumes the DSCP and PHB to remain unchanged when passing a tunnel (may also be an MPLS tunnel). The uniform model is out of scope of diffserv-intercon.
-       The pipe model assumes the DSCP to remain unchanged when passing a tunnel. The pipe model is out of scope of diffserv-intercon.
-       The short pipe model tolerates or requires a DSCP rewrite at interconnection points. Diffserv-intercon proposes to indicate a desired PHB by a defined DSCP at an interconnection point. Any DSCP may be re-written by the receiving domain.

This is not to say, that uniform model or pipe model should not be supported. It just to indicate what's within and what's out of scope of diffserv-intercon. The draft doesn't define the uniform and pipe model to be out of scope yet, the next version will (unless there's disagreement on this aspect).

Regards,

Ruediger