Re: [Ieprep] proposed charter 5 priority levels

In message <6.2.1.2.0.20060926190508.03463c30@ihmail.ih.lucent.com>
John Rosenberg writes:
>  
> At 05:52 PM 9/26/2006, ieprep-request@ietf.org wrote:
>  
>  >Date: Tue, 26 Sep 2006 12:56:15 -0400
>  >From: Curtis Villamizar <curtis@occnc.com>
>  
>  >In message 
> <OFBAA95066.05652C8C-ON852571F5.004A9C8A-852571F5.004B6690@csc.com>
>  >Janet P Gunn writes:
>  >>
>  >>
>  >> As RFC 4412 makes perfectly clear, the RPH serves a dual role of signalling
>  >> priority across an IP network (e.g. from an originating circuit switched
>  >> access network to a terminating circuit switched access network) as well as
>  >> signalling  priority within the IP network.
>  >>
>  >> For each of the namespaces described in RFC 4412, the number of priority
>  >> values (5 in most cases, 6 in one) is driven by the former role, based on
>  >> the number of priority values in use, or being considered, in the access
>  >> network priority scheme.
>  >>
>  >> The issue of how many priority levels to differentiate WITHIN the IP
>  >> network is an issue currently being addressed by vendors and providers.
>  >>
>  >> Janet
>  >
>  >
>  >Janet,
>  >
>  >You are right, but you may be just focusing on SIP which is one peice
>  >of the puzzle.
>  >
>  >RFC 4412 does not make it perfectly clear whether we need 1 DSCP code
>  >point, EF, or 5 DSCP code points (IP Prec 0-4?)  or 15 DSCP code
>  >points (the 4 AF classes plus one more AF class.  Or is it some
>  >multiple of 6?  This RFC doesn't even mention DSCP.
>  >
>  
> Let me add my voice and suggest that we're really in need of some mechanism 
> that allows the application (e.g. MLPP, ETS, whatever) to determine a 
> "priority level" for a session and indicate to the endpoint that it's 
> serving what DSCP value that the endpoint should use for its bearer packets.
>  
> It could be a header or parameter in some subset of SIP messages, it could 
> be an attribute in SDP, it could be something else entirely. I think the 
> whole question of how many and which DSCP values should be used for some 
> arbitrary application is a little premature if we don't have a way for the 
> application to get that value used.
>  
> John Rosenberg

The discussion just went full circle.  We already have a SIP priority
in RFC4412.  Use of DSCP is only touched on in RFC4190.  Both the SIP
priority and DSCP value can be carried in microflow RSVP
(draft-briscoe-tsvwg-cl-architecture-03.txt).

Which DSCP value seems to be an open issue for now.  Discussion seems
to favor a new DSCP EF-like value for ETS.

Curtis

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