[Serusers] Re: [Users] TM : retransmission timers

[sip]

Well... the TM bug may not be earth-shattering, but it's most decidedly
important. One of the functions we have that our users LOVE is the ability to
set their own timeout values for voicemail. We had had a default value that we
thought would make everyone happy, but soon discovered that many would
complain that it was too long, and many would complain that it was too short.

Having had many users who came along from asterisk-based services, where
setting individual timeout values is rather straightforward and easy.

One of the things we've been struggling with has been the timing values. While
it may not be important in the scheme that it's not ACTUALLY
service-affecting, I can assure you, if you offer a service, and it doesn't
work as prescribed, the consequences can be deadly. You shake user-confidence
-- and that sort of thing travels VERY quickly by word of mouth. It's so very
hard to gain users, and so very easy to lose them to a competitor -- even if
that competitor doesn't offer the same options. For what good are options that
only work sometimes?

SO... in short... yeah... I'm really happy that the timer stuff has been fixed
in Ottendorf. Of course, it'll be a LONG time before we can migrate the
production systems to it, but it gives me something to look forward to.

N.

On Thu, 30 Nov 2006 12:19:03 +0100, Andrei Pelinescu-Onciul wrote
> On Nov 29, 2006 at 14:05, Kim Il <kim_il_s at yahoo.com> wrote:
> > this is getting more and more confusing. The one side says this is a bug,
the other says it is a feature. I will try to summarize my understanding till now:
> 
> I believe we  better stop this line of discussion at least for now 
> and instead concentrate on fixing the technical problems that were revealed
> on both sides. I wouldn't want it to hinder possible future
> collaboration.
> 
> > *  openser claims that they improved something and the ser guys say this
fix is useless. Daniel, Bogdan could you plesase  explain what is really
behind this improvement (Sorry Weiter, but your explanation is far from being
sufficient).
> 
> I don't know exactly what are you referring to ("something"?), but I 
> don't remember claiming that an openser fix was useless (at least I 
> haven't, I might have implied that something, IMHO was not as 
> important as claimed, but not that was useless).
> 
> > * The ser guys show that openser is inferior to ser but Bogdan replies
this is on purpose (because otherwise a strange race situation can occur which
Andrei tells us is negligable).
> 
> Actually, the claim was along the lines that tm (the statefull part 
> of the sip stack in ser) and/or the core performance was inferior.
> 
> The bug that Bogdan discovered is not negligible. I wanted to point out
> that it was not as important as suggested.
> This probably deserves a better explanation, so that people without
> ser-internals knowledge can understand.
> First of all variable timers in this context mean the possibility to
> set different values for  the fr_timer and fr_inv_timer at runtime
> 
> (e.g. in function of some user preferences/avps or some special 
> script logic) as oppossed to having some fixed (but configurable) values.
> What really matters here is the fr_inv_timer. The fr_inv_timer is the
> time that ser waits for a final response on an INVITE transaction
> _after_ a provisional response was received (e.g. 180 Ringing). This 
>  roughly corresponds to the Timer C from the sip rfc (rfc3261).
>  According to the sip rfc both fr_tiemr and fr_inv_timer should be fixed
> and _not_ configurable. However in practice it makes sense to change 
> them
> (especially the fr_inv_timer), to implement services such as 
> redirect to voicemail after x seconds. The most common use of the 
> variable timers is user (or group) configurable voicemail 
> redirection. This means that the user is somehow able to configure 
> the "ringing" interval after which a caller will be redirected to 
> his voicemail. If variable timers are not used, the voicemail config 
> option would include only on or off (the ringing time before 
> voicemail redirection wouldn't be configurable, it would be the same 
> for all the users). Now what the bug did, was that it could cause 
> the extension of fr_inv_timer to the fr_inv_timer of another 
> transaction, if _different_ variable timers were used and some race 
> occured (note that the probability of hitting the race is quite high 
> if lots of variable fr_inv_timers with different values are used and 
> the system is very busy). This IMHO is not such a big problem since 
> in the case when you are hit by it, it  really doesn't break 
> anything important (I don't see sometimes redirecting later to 
> voicemail as such a big problem, OTOH people might use it for other 
> stuff).
> 
> > * I will not get into the history discussion -which I have already touched
in previous mails, let alone those mails about respect and the other stuff I
could not really see how they relate to this discussion.
> > I would really appreciate if these points were clarified -I have the
impression the ball is now with Daniel and Bogdan. So plesse Bogdan do not
hold to your one mail policy and help clarifying this and provide a bit more
of details on the improvements of openser to core and tm.
> > 
> > I believe Andrei has made a good suggestion that it is in the interest of
the entire community to cooperate and divide the areas of interest. By
combining the great work the openser guys have done in the area of
documentation and featutres with the work of ser in the area of core we will
all get an even better ser/openser.
> 
> In fact even if we can't reach an agreement in dividing areas, small
> cooperation like on fixing/improving code that is the same in both
> versions would still be good.
> I would say that even a friendly competing approach would be better then
> nothing (with comparisons, benchmarks a.s.o), it points out problems 
> in both versions and serves as a motivation to improve.
> 
> Andrei
> [...]
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