>> This process continues so that retransmissions occur with an exponentially >> increasing interval that caps at T2.
I think this actually means > - Initially => T1 = 0.5s > - Fires => MIN(2*T1, T2) = 1s > - Fires => MIN(4*T1, T2) = 2s > - Fires => MIN(8*T1, T2) = 4s > - Fires => MIN(16*T1, T2) = 4s 2,4, 8, 16... which is exponential. On Wed, Apr 6, 2011 at 10:06 PM, Iñaki Baz Castillo <[email protected]> wrote: > Hi, RFC 3261 section 17.1.2.2 states that: > > If an > unreliable transport is in use, the client transaction MUST set timer > E to fire in T1 seconds. If timer E fires while still in this state, > the timer is reset, but this time with a value of MIN(2*T1, T2). > When the timer fires again, it is reset to a MIN(4*T1, T2). This > process continues so that retransmissions occur with an exponentially > increasing interval that caps at T2. The default value of T2 is 4s, > and it represents the amount of time a non-INVITE server transaction > will take to respond to a request, if it does not respond > immediately. For the default values of T1 and T2, this results in > intervals of 500 ms, 1 s, 2 s, 4 s, 4 s, 4 s, etc. > > I've calculated those intervals and can't get same values: > > Timer E: > - Initially => T1 = 0.5s > - Fires => MIN(2*T1, T2) = 1s > - Fires => MIN(4*T1, T2) = 2s > - Fires => MIN(4*T1, T2) = 2s > - Fires => MIN(4*T1, T2) = 2s > ... > > So the resulting intervals are 500ms, 1s, 2s, 2s, 2s, 2s, etc. > In short, it's obvious that MIN(4*T1, T2) will always be 2 seconds! it > can never reach 4s. > > > IMHO the text should say: > > If timer E fires while still in this state, > the timer is reset, but this time with a value of MIN(2*TIMER_E, T2). > > And remove the line about "When the timer fires again, it is reset to > a MIN(4*T1, T2) > > So we get: > > Timer E: > - Initially => T1 = 0.5s > - Fires => MIN(2*TIMER_E, T2) = 1s > - Fires => MIN(2*TIMER_E, T2) = 2s > - Fires => MIN(2*TIMER_E, T2) = 4s > - Fires => MIN(2*TIMER_E, T2) = 4s > > Am I wrong? Thanks a lot. > > > PS: Sorry for the cross-posting, I don't know which maillist is better > to report it. > > > -- > Iñaki Baz Castillo > <[email protected]> > > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
