[Users] TM : retransmission timers

[Christian Schlatter]

Greg Fausak wrote:
> Hello,
> 
> I believe this is a well known bug.
> Granularity of timers is 1 second.  So, if you sign up for a timer to
> be fired in 1 second it will happen anywhere between 0 seconds and 1 
> second.
> 2 seconds will happen between 1 and 2 seconds.  I usually set up my
> timers to be 2, 2, 4, 8.  There are VOIP providers that are pretty 
> sticky about
> the first 500ms.  If you are using one of them you're out of luck.

Yes, there is a timer process that wakes up every second to perform 
retransmissions. I was actually quite surprised that OpenSER, which is 
known to be very standards compliant, does not follow the RFC 3261 
retransmission timeouts. On the other hand, the RFC 3261 timeout values 
are just suggestions and standards compliant SIP UA must accept shorter 
timeouts. Still it would be nice if OpenSER would support sub second 
timers, this would allow for shorter fail-over times.

Christian

> 
> I believe SER has made timer changes to support more exact timer
> intervals.  They are a completely different camp, with a different feature
> set (although they share the same roots).
> 
> -g
> 
> 
> On 11/7/06, Jean-François SMIGIELSKI <jf-smig at ibelgique.com> wrote:
>> Hello,
>>
>> I made strange observations about the intervals between 
>> retransmissions with the TM module.
>> In my experiments,  I used the default parameters for the TM module 
>> timers, and I  sent an INVITE that cannot receive answers (it has a 
>> well  known R-URI pattern that is forwarded to a place and port that 
>> nobody listen).
>>
>> When reading RFC3261, I expected to see intervals between 
>> retransmissions of |500ms|1s|2s|4s|8s|16s|. 7 transmissions, during 32s.
>>
>> But with OpenSER, (I have tested with the debian package 1.1.0-5 on a 
>> debian etch, and the cvs sources for 1.1.0 or 1.0.1compiled by 
>> myself), I can see intervals like <500ms, 2s, 4s, 4s,4s, ... until 26s 
>> are spent (9 sendings). The first interval is sometomes very short 
>> (40ms).
>>
>> Altough I like the sequence of 4s separated transmissions, I do not 
>> know why the first interval is so short, and why there is no sending 
>> after 1s.
>>
>> Did anybody observed such behaviours? Are they normal?
>>
>> Thanks in advance!
>>
>> JF Smigielski.
>>
>>
>> ________________________________________________________________________
>> iBELGIQUE, exprimez-vous !
>> http://web.ibelgique.com/
>>
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>>
>>
>>
> 
> 

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