[Ieprep] Question about RSVP based preemption

Regarding the example in Appendix A of draft-baker-tsvwg-mlpp-that-works-02.txt, it seems that RSVP based preemption may unnecessarily drop low priority calls in cases were the preempting call is not completed to the original callee - in cases where the callee's UAS is alive and well but the call for some reason goes unanswered and is forwarded to an alternate party or a global attendant somewhere else on the network.

If you have a network snippet like......

	    Alt Party	   R Talker
	       |               |
             |               |
F Caller-----N---------------N------F Callee
                             |
                             |
                           R Talker

Where the 2 "R Talkers" are on an existing Routine Call, N are routers where RSVP preemptions may occur, and F Caller / F Callee are participants in a Flash call being set up (and assuming that the current b/w requirements are such that the F's cannot make their call w/o preempting the R's).

>From the example in the draft, it looks like the R's will receive the RSVP preemption messages before F Callee's phone rings to prevent dead rings.  Is this correct?  Is yes, and F Callee doesn't answer the phone for any reason, F Caller will be redirected to F Callee's Alternate Party.  In this case the Routine call is unnecessarily preempted.

Is my understanding of how this works correct?

Is it possible for the RSVP preempting routers to delay the tear down of low priority calls until the high priority stream actually starts?  I.e. Mark the low priority stream for preemption, but don't actually tear it down until the b/w is at capacity.

Thanks,

Chris

Christopher Eagan
Software Engineer
Lockheed Martin, IS&S
(301) 240 - 6328

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