[asterisk-dev] SIP Stack Research

[Saúl Ibarra Corretgé]

Joshua Colp wrote:
> Hola,
>
> (Apologies for the semi-long email)
>
> As Mark mentioned in his earlier email I've been working on researching
> viable SIP stacks for the new SIP channel driver. I've scoured the far
> reaches of the internet looking for new stacks that may have come into
> existence since my previous Asterisk SCF research but in the end the
> three that came to the top were Sofia-sip, Resiprocate, and pjsip.
>
> You can find my research on them at
> https://wiki.asterisk.org/wiki/display/AST/SIP+Stack+Research
>
> I've detailed what I looked at and the impressions I got for each. This
> is by no means a deep deep deep analysis as that would take considerably
> more time. What it does cover though is the community for each project,
> how easy it is to use, general impression on features, interoperability,
> and (in my opinion) most importantly documentation.
>
> Through doing all of this research I have learned that there is no
> perfect SIP stack, but all of the ones I mentioned will do what we need.
> No matter which one you choose though you are effectively giving up
> something you could have gotten with another one so we have to find a
> balance. I think our balance should be towards a stack that has great
> documentation, is easy to use (and expand), provides the features we
> want, and still has an active community.
>
> After examining the three options I've ordered them as follows according
> to my personal opinion against the above:
>
> 1. pjsip
> 2. Resiprocate
> 3. Sofia-sip
>
> But Josh, why did you order it as such?!?
> Good question, Josh.
>
> The documentation for pjsip is great and makes it easy to learn exactly
> how to use it and what is going on. The general architecture of it makes
> extending it *extremely* easy and you can inject your own modules at
> many different layers. The project itself is still being actively
> developed and maintained. The time required to get up to speed and use
> pjsip is also very low since there are people in the Asterisk community
> who are familiar with it and have used it.
>
> Resiprocate came second because the documentation is not as complete or
> expansive as pjsip, 'nor is the higher level (APIs that reduce the
> amount of code we have to write) feature count. It would also be more
> difficult to use it with Asterisk as it is C++ based, and this would
> also decrease the number of people who could help with that integration.
>
> Sofia-sip came last because it did not have as good of documentation as
> resiprocate or pjsip and the project itself seems to have become
> stagnant. It also lacks as many higher level features as pjsip.
>
> The purpose of this email is to bring about discussion on this subject
> as a whole and try to reach a conclusion on which SIP stack would be the
> best in the eyes of the community.
>
> Thanks for reading this long email and I look forward to the discussion.
>
> Cheers,
>

Hi Josh,

As you know, my experience is basically with PJSIP, I just played with 
Sofia very briefly years ago so I don't remember much.

The only thing that concerns me a bit are threading issues with PJSIP. 
We have run into deadlocks while developing SIP SIMPLE SDK, and the main 
SDK user is Blink, a client application, not a server. There are tons of 
clients implemented with PJSIP, but most of them use the pjsua API, with 
has a giant lock. Servers with PJSIP? Not many, at least in the Open 
Source multiverse.

Back in 2006 FreeSWITCH attempted to implement mod_pjsip, to use it as 
their SIP stack, but they gave up and threading issues was apparently 
one of the reasons. People from PJSIP were involved FWIW. Yes, 6 years 
is a long time, but AFAIK, PJSIP hasn't changed it's internal design. 
Also, FS and Asterisk are different things, but I think t's worth 
considering, nevertheless.

Now, I guess that depending on how / at what level the integration is 
made we may not run into these issues in Asterisk. Since you guys 
already used it in SCF, what was the experience there? Were high load 
benchmarks performed?

I don't know much about reSIProcate, but PJSIP has its own proactor and 
Sofia its own reactor, how would any of these be integrated into 
Asterisk's current architecture, at a first glance?

Keep up the good work!


Cheers,

-- 
Saúl Ibarra Corretgé
http://saghul.net/blog | http://about.me/saghul