[SIP Beyond VoIP] couple of sylkserver questions

Juha Heinanen jh at tutpro.com
Wed Nov 14 09:41:48 CET 2012

Saúl Ibarra Corretgé writes:

> The participants list is fetched with a subscription to the
> 'conference' event. SIP SIMPLE (the SDK) will always subscribe to such
> event if the remote Contact header contains ';isfocus'. Now
> sip-session doesn't print participants, but it wouldn't be hard at all
> to do so, since it already subscribes to such event. Also, what
> RFC4353 refers to as 'fetch' is just sending a SUBSCRIBE with expires
> 0, in order to trigger a NOTIFY with the participants update, but in
> our case we already have such list though is not printed anywhere.


i gave subscribe with expires=0 a try and got 423 Interval Too Brief

T 2012/11/14 10:35:54.412755 -> [AP]
SUBSCRIBE sip:+35892345671*3655*8681 at cf.test.fi SIP/2.0.
Via: SIP/2.0/TCP;branch=z9hG4bK02c3.1f2e4bd2000000000000000000000000.0.
To: <sip:+35892345671*3655*8681 at cf.test.fi>.
From: <sip:jh at test.fi>;tag=50a357ea62873.
Call-ID: 50a357ea62873.
Content-Length: 0.
User-Agent: OpenXg SIP Proxy  (3.4.0-dev4 (i386/linux)).
Contact: <sip:click2sub at>.
Event: conference.
Expires: 0.
Accept: application/conference-info+xml.
Allow-Events: conference.

T 2012/11/14 10:35:54.413415 -> [AP]
SIP/2.0 423 Interval Too Brief.
Via: SIP/2.0/TCP;received=;branch=z9hG4bK02c3.1f2e4bd2000000000000000000000000.0.
Call-ID: 50a357ea62873.
From: <sip:jh at test.fi>;tag=50a357ea62873.
To: <sip:+35892345671*3655*8681 at cf.test.fi>.
Server: SylkServer-2.2.1.
Content-Length:  0.

i think that according to rfcs, subscribe with expires value 0 should 
result in a 200 response as well as an immediate single NOTIFY 
indicating that the subscription has been terminated.

is this a bug in pjsip stack?

-- juha

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