[SR-Users] Web softphone using websockets against Kamailio

[Peter Dunkley]

Hello,

This topic has been covered many times on the Kamailio/SIP Router lists
and the answers you require can be found by searching the lists.

I will briefly recap:

      * SIP signalling and media are totally separate things
      * SIP over WebSockets will allow an HTML5 based client to exchange
        signalling information with standard soft-phones and
        hard-phones.  However, this does not mean that the media will
        interwork
      * HTML5 media streaming uses WebRTC.  WebRTC mandates the use of
        the RTP/SAVPF media profile which is not yet supported by many
        soft-phones, hard-phones, or media servers


This means that, provided you have configured Kamailio and sipml5
correctly, you can get the signalling part of a call working but you
will almost certainly have media issues.  Kamailio is a SIP signalling
device, not a media device, so fixing these media issues is outside of
the scope of Kamailio.

You do have a few of options with regards to the media but they are
limited at the moment.

      * You can try and find a phone/client that supports RTP/SAVPF (the
        only ones I know of are the Doubango clients and they sometimes
        have other issues).
      * You can use a media server to convert from RTP/SAVPF (Asterisk
        supports this in theory, but does have issues - I believe there
        are fixes in the latest Asterisk trunk if you want to compile it
        yourself - and there may be some non-open-source media servers
        available).
      * You can use an RTP Proxy to convert from RTP/SAVPF (erlrtpproxy
        has this feature on the roadmap, but I don't know whether it is
        available yet).


As for IE support, your guess is as good as mine.  Microsoft has its own
agenda and has recently been pushing the competing CU-Web-RTC
specification.  I have a personal opinion about how things will
eventually evolve but no facts to share here - I don't believe anyone
outside of Microsoft could tell you what will actually happen with IE.

Regards,

Peter


On Mon, 2013-01-28 at 20:45 +0200, Pirjo Ahvenainen wrote:

> Greetings gurus!
> 
> I'm playing with an idea to create a web based softphone (html5 + no
> installations for the end user) and use Kamailio's websocket module
> for backend. I'd love to hear about your comments, challenges and
> successes using such configuration. Is it a feasible way to construct
> a softphone even today when even IE9 does not support websockets, as
> such? I'm sure IE9 will end up in specs as a must-support platform.
> 
> A collegue tried using sipml5 with webrtc against a SnomONE pbx (I
> know... ;)), and said there's no way it can work, but I'm not
> convinced the idea itself wouldn't work.
> 
> It would help me lots if I could make a simple example using Kamailio
> with SIP over websockets, can you comment on how much effort do I need
> on Kamailio side to make this work? Do I need off-default config
> scripting, or is it enough to just set up the module and set the
> parameters? And even with the risk of stepping a little off topic, if
> anyone has worked on web based softphones, I'd love to hear if you can
> recommend on how to approach this.
> 
> Cheers,
> Pirjo
> 
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-- 
Peter Dunkley
Technical Director
Crocodile RCS Ltd
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