Re: Fwd: Comments on draft-niemi-sipping-event-throttle-08.txt

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Hi Michale,

sorry to be late answering this mail.
see my comments in line.

Sal

Michael Froman wrote:
Resending in case this got lost in the noise over the last week.

Begin forwarded message:

From: Michael Froman <mfroman@xxxxxxxxxxxx>
Date: March 4, 2009 10:00:10 AM CST
To: sipping@xxxxxxxx
Subject: Comments on draft-niemi-sipping-event-throttle-08.txt

Hello all,

I have a question/concern about the closing paragraphs of 4.2.2, 5.2.2 and 6.3.2. Each of these paragraphs deals with retransmissions of NOTIFY requests and resetting the throttle (or force or average) based on the completion of the previous transaction. Given that the notifier and the subscriber can have different ideas of when the transaction ends (up to T1 I believe), I want to verify the reasoning behind these paragraphs.
[Sal] here the last paragraph

  Retransmissions of NOTIFY requests are not affected by the throttle,
  i.e., the throttle only applies to the generation of new
  transactions.  In other words, the throttle is reset only after the
  previous transaction has completed.


Is the point that throttle/force/average not break the retransmission mechanism
[Sal] that is exactly the point. Throttle/force/average do not break or modify in any way the retransmission mechanism.
or that, for example, retransmissions modify the time between forced NOTIFYs by the time taken for the retransmissions to successfully complete the transaction? An example is the case when the NOTIFY gets to the subscriber quickly, but the 200OK is slow to make it back to the notifier. Start with a force value of 2 seconds. The subscriber thinks the transaction is over and is now expecting a forced NOTIFY 2 seconds from now. The notifier has not completed the transaction. The next NOTIFY from the notifier can happen anytime up to T1 + 2 sec.

I agree that throttle/force/average should not interfere with the normal retransmission mechanism. However, I don't agree that waiting for the transaction to complete before starting the throttle/force/average timer is going to give much benefit (or always predictable results).
[Sal] While I agree that this behaviour (waiting for the transaction to complete) can not always give "predictable" results and that is bad especially if you want use it to track the location of a UA, However making "throttle/force/average" timers independent (so to say) from the the retransmission mechanism can lead to situation where the timer fires and then you should send out a new NOTIFY when there is still a retrasmission of a previous one. Any thought on how to solve this situation without break the retransmission mechanism?




Thanks,
Michael.




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