[Sip] -resource-priority-05.txt: Comments and Recommendations
"Corey W. Alexander" <coreya@nortelnetworks.com> Thu, 11 November 2004 23:11 UTC
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From: "Corey W. Alexander" <coreya@nortelnetworks.com>
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Subject: [Sip] -resource-priority-05.txt: Comments and Recommendations
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This should spur some discussion... I'd rather send this directly to the authors, but to keep everything out in the open... I spoke briefly with Mr. Polk following the IEPREP session on Tuesday. I had three general questions. I'm paraphrasing the responses, and so invite James to correct me if I'm misrepresenting him here. 1. Why support multiple namespace/priority (n-p) values in a single message, in one or more R-P headers? And if supported, should not the n-p values in the message equate to the same priority level (for example, dsn.flash and q735.1 would be equal)? Would it not be better to support only one n-p value per message, and recommend that a proxy/gateway between networks supporting two different namespaces handle mapping n-p values? ---- There may be/are networks which would support multiple levels. The draft is not dictating that there must be multiple levels. ---- As for having the n-p levels be "equal", James cited a GETS call with a specific precedence which becomes a Routine call on the DSN. ---- Having a proxy/gateway mapped between namespaces is an viable alternative. 2. Is it wise or valid to explicitly allow a proxy to "upgrade" or "downgrade" the n-p values in a message? ---- I'm coming at this from the DSN perspective, but wps and/or ets may allow this kind of thing. While the DSN/DSRN/(Q735) would not, that does not invalidate the concept. 3. With "preferential treatment" of messages based on R-P content, should not scenarios be considered and listed in which a lower priority message would need to be handled before a higher priority message? My example: it would be wise to handle a BYE message with dsn.routine before an INVITE with dsn.flash-override... At least in certain situations, say when the BYE is sent as a result of a preemption event (which the Reason header should likely indicate). ---- Certainly something to consider, especially for DSN. Having witnessed the majority of the discussion on this draft in the final SIP session, and stepping back from the questions I had, it occurs to me that, while the information presented is not invalid, it is certainly confusing, to a varying degree. In my opinion, the confusion comes from trying to define (describe/outline, whatever) the behavior of the various namespaces, while at the same time intending to keep draft general, and the use of the R-P header open to those who implement it. Right before the comments on this draft were brought to a close, the thread was leading to there ultimately being independent documents which would describe the overall behavior of networks which implement one or more of these namespaces. RECOMMENDATION: Any namespace-specific behaviors should be relegated to documents specific to the namespaces themselves. For instance, there are currently a number of documents, and certainly other to come, dealing with the requirements/architecture/implementation of Assured Service (MLPP in IP): draft-baker-tsvwg-mlpp-that-works-02.txt draft-pierce-tsvwg-assured-service-req-01.txt draft-pierce-tsvwg-assured-service-arch-01.txt draft-pierce-tsvwg-pref-treat-examples-01.txt It is in documents like these - more specifically, documents specific to expected behaviors - where the use of the R-P header should ultimately be laid out. I would like to see the R-P draft limited to - a general description of what the header is: What is a namespace? What is the priority values mean? Why is it needed? Basically, background and definitions, but NOT explicit behaviors. - the format of the Resource-Priority header - 417 response code - error conditions --- If the R-P header is not supported: 420 --- If the n-p value is not supported or unknown: 417 *** This document does not have to define those circumstances in which each defined namespace considers the n-p value unsupported. - A MINIMUM number of namespaces. *** I would recommend providing only a single generic namespace, with 5, 6, whatever, priority values, and leave the actual namespace definitions (dsn, dsrn, ets, wps; and q735, if necessary) to documents specific to those namespaces/architectures. This would remove all of the confusion. No need to describe the behaviors expected with the current namespaces, let applications specific to the namespaces to that. Further, the document could then keep the strict, semi-strict, and loose mode concepts intact (or with modification) without interfering with existing behaviors in the current namespaces. New namespaces, when defined, can align themselves with these modes, or define their own behaviors. Finally, since preferential treatment of messages would likely find greater use outside of a private network than preemption, I would also recommend one more thing. If the suggestion of a single generic namespace in this draft is taken, behaviors surrounding the concept of preferential treatment should be included for this namespace. Digest and comment. -- Corey W. Alexander _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use sip-implementors@cs.columbia.edu for questions on current sip Use sipping@ietf.org for new developments on the application of sip
- [Sip] -resource-priority-05.txt: Comments and Rec… Corey W. Alexander