>Hello,
>
>What if the values of the timers are absolute relative
>to the first INVITE sent ?

draft-ietf-sip-rfc2543bis-09 says

17.1.1.2 Formal Description

[skip]
   If an unreliable transport is being
   used, the client transaction MUST start timer A with a value of T1.
   If a reliable transport is being used, the client transaction SHOULD
   NOT start timer A (Timer A controls request retransmissions). For any
   transport, the client transaction MUST start timer B with a value of
   64*T1 seconds (Timer B controls transaction timeouts).

   When timer A fires, the client transaction MUST retransmit the
   request by passing it to the transport layer, and MUST reset the
   timer with a value of 2*T1. The formal definition of retransmit
   within the context of the transaction layer is to take the message
   previously sent to the transport layer and pass it to the transport
   layer once more.

   When timer A fires 2*T1 seconds later, the request MUST be
   retransmitted again (assuming the client transaction is still in this
   state). This process MUST continue so that the request is
   retransmitted with intervals that double after each transmission.
SS>                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   These retransmissions SHOULD only be done while the client
   transaction is in the "calling" state.

Looks like Your proposal is going to work. But it is against the RFC.

Sergey.

>Time
>
>0 INVITE1 (retransmit after 500) (t0)
>500 INVITE2 (retransmit after 1000) (relative to t0)
>1000 INVITE3 (retransmit after 2000) (relative to t0)
>2000  INVITE4 (retransmit after 4000) (relative to t0)
>4000  INVITE5 (retransmit after 8000) (relative to t0)
>8000  INVITE6 (retransmit after 16000) (relative to t0)
>16000 INVITE7 (retransmit after 32000, but this is equal
>to transaction timeout, so no retransmit) (relative to t0)
>32000 Would send INVITE8, but transaction timed out.

>In that case, the respective delays for response are 0.5,
>0.5, 1, 2, 4, 8, and 16 seconds, with no odd delay at the end.

>This seems to make more sense.

>-Robin Lavall�e


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