[cisco-voip] SIP session timer in IOS gateway

[Daniel Pagan]

I should be more specific... the min-SE specifies the minimum value the UAS is willing to accept from the Session-Expires header sent by the UAC. If your INVITE has an SE if 1800, and the incoming dial-peer has a min-SE of 3600, then CUBE will reply back to the UAC with a 422 final response - this 422 will contain its own min-SE header with value of 3600. The UAC should ACK the 422 and *should* follow-up with another INVITE where the Session-Expires timer value is 3600. This is one way to force CUBE to manipulate the incoming SE. I felt my previous explanation was missing some information and might have been a bit too vague.


"If the response to a session refresh request is a 422 (Session Interval Too Small) response message, then the UAC MAY retry the request."



CUCM, if it's the UAC, will retry the INVITE. I can't speak to other call-agents though. But I still suggest, if possible, to address the main problem of your session expiration.



Hope this helps.

- Dan


From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Daniel Pagan
Sent: Friday, September 23, 2016 4:12 PM
To: Norton, Mike <mikenorton at pwsd76.ab.ca>; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] SIP session timer in IOS gateway

Adjusting the SE on standard CUBE is not possible from what I've experienced and tested. One way around it though is to set your Min-SE timer on the incoming dial-peer on CUBE. The UAC sending the INVITE will receive a 422 response back, from CUBE, and will include an updated min-se timer. The new min-SE value in the 422 will then be copied, by the UAC, into the Session-Expires header within a second INVITE. The question I feel I should ask though... is why try manipulating the SE/minSE timers to get around a failed session refresh instead of addressing the session refresh itself? Of course this is only masking another problem.

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From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Norton, Mike
Sent: Friday, September 23, 2016 4:01 PM
To: cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: [cisco-voip] SIP session timer in IOS gateway

I'd like to adjust IOS's behavior around the SIP session-expires timer. Wondering if anybody knows if the command I need exists...

According to RFC 4028:

"If the side not performing refreshes does not receive a session refresh request before the session expiration, it SHOULD send a BYE to terminate the session, slightly before the session expiration."

My problem stems from the fact that "slightly before" is left open to the imagination. The RFC "recommends" not more than 32 seconds but does not have any specific "requirement." The default behaviour of IOS seems to use a longer value. I.e., it sends the BYE a little too prematurely for my situation. I need IOS to let the timer get closer to expiring before it issues the BYE.

I know it's a long-shot, but someone please tell me there is a command for adjusting this! Not finding anything in the docs. Hoping to avoid having to disable the session timer or crank it up to 11. I love SIP interop, it's so much fun! :-(

-mn

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