[Freeswitch-users] Freeswitch and RFC4028

[Barnaby Ritchley]

Hi All

We have a situation where FS seems not to behaving correctly with session timers.

Call originates from remote party with invite as per:

INVITE sip:+1234 at 1.2.3.4;user=phone SIP/2.0 
Max-Forwards: 69 
Session-Expires: 3600;refresher=uac 
Min-SE: 600 
Supported: timer, 100rel 
To: +1234 <sip:+1234 at 1.2.3.4;user=phone> 
From: <sip:+5678 at 5.6.7.8;user=phone>;tag=381443 
P-Asserted-Identity: <sip:+5678 at 5.6.7.8> 
Call-ID: 1333524918-9038500 at xxxxx
CSeq: 1 INVITE 
Allow: CANCEL, ACK, INVITE, BYE, OPTIONS, INFO, PRACK, UPDATE 
Via: SIP/2.0/UDP 7.8.9.1:5060;branch=z9hG4bKab17954781a678af6dfd6916593dc954 
Contact: <sip:+5678 at 5.6.7.8:5060> 
Expires: 330 
Content-Type: application/sdp 
Accept: application/sdp 
Content-Length: 387 


Here you can see the UAC supporting timer, and specifying a session expires of 3600.

FS responds with 100 trying (not relevant) then 180 runing (also not relevant) then 200OK as per:

SIP/2.0 200 OK 
From: <sip:+5678 at 5.6.7.8;user=phone>;tag=381443 
To: +1234 <sip:+1234 at 1.2.3.4;user=phone>;tag=UrcX58SSF2Nrm 
Call-ID: 1333524918-9038500 at xxxxx
CSeq: 1 INVITE 
Contact: <sip:+1234 at 1.2.3.4:5060;transport=udp> 
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, UPDATE, INFO, NOTIFY 
Supported: timer, precondition, path, replaces 
Allow-Events: talk, hold, refer 
Session-Expires: 3600;refresher=uac 
Min-SE: 600 
Content-Type: application/sdp 
Content-Disposition: session 
Content-Length: 249 


So, here freeswitch is responding with the session-expires and refresher UAC.  Then after 60 mins, the call is dropped as FS sends a Bye to the UAC because it does not receive a session refresh.  Here is the Bye:

BYE sip:+5678 at 5.6.7.8:5060 SIP/2.0 
Via: SIP/2.0/UDP 178.255.58.28;rport;branch=z9hG4bK2vm55Zp2D6vHm 
Max-Forwards: 70 
From: +1234 <sip:+1234 at 1.2.3.4;user=phone>;tag=UrcX58SSF2Nrm 
To: <sip:+5678 at 5.6.7.8;user=phone>;tag=381443 
Call-ID: 1333524918-9038500 at xxxxx
CSeq: 27563136 BYE 
Contact: <sip:+1234 at 1.2.3.4:5060;transport=udp> 
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, UPDATE, INFO, NOTIFY 
Supported: timer, precondition, path, replaces 
Reason: SIP;cause=408;text="Session timeout" 
Content-Length: 0 

When we raised this with the UAC, their response is that the reason they are not refreshing the session is because FS should be sending a Require: timer; header in the response, so their UAC thinks that session timers are not in use.

This is documented in para 9 of RFC4028:

If the refresher parameter in the Session-Expires header field in the
2xx response has a value of 'uac', the UAS MUST place a Require
header field into the response with the value 'timer'.  This is
because the uac is performing refreshes and the response has to be
processed for the UAC to know this.

It appears the FS is not doing this, but is hanging up the call anyway, so we are getting dropped calls that are around the 60 mins mark.

Whats everyones view on this?  It would seem logical that if FS is not sending requires in the return 200, that the UAC will think that the session timers are not being used in the session, and therefore will not refresh it.


Brgds

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