CUBE & Min-SE timer

[Gordon Ross]

We've got an issue whereby CUBE is terminating calls after 30 minutes. At first glance, this is understandable: The default session timer is 30 minutes in CUBE. But as part of the call setup, the ITSP is sending a "Min-SE: 600" header - which surely is setting the session timer to 10 minutes.

So, according to my logic, as a Min-SE header is present, surely shouldn't CUBE be using that value instead of its own internal setting?

I could just ramp up the session timer parameter in CUBE, but that would be solving the symptom rather than the cause.

A follow up question: Is the Min-se setting per leg or for the complete path of the call. i.e. I have ITSP <> CUBE <> CUCM. Is it valid that the CUBE<>CUCM leg has a different Min-SE than the ITSP <> CUBE leg? Or does CUBE just blindly pass the Min-SE header between the ITSP & CUCM?

Thanks,

Gordon

[R0g22]

Who acts as the session refresher for these calls ? Do you have a log that we can look at ?

[Gordon Ross]

The example call I have is an inbound call from the ITSP to CUCM. The ITSP is sending a SIP packet with a Min-SE header, so I assume CUBE (Or is it CUCM?) is supposed to perform the refresh.

Gordon.

[R0g22]

Not really. It's an inbound call to the CUBE will act as a UAS. Do you see a Refresher param in an UPDATE or something ? Can you share the log file here ?

[Jonathan Schulenberg]

In addition to Nipun’s questions, Min-SE is the minimum acceptable value. In other words, refreshing more frequently than once every 600 seconds is not acceptable to the ITSP.
https://tools.ietf.org/html/rfc4028

CUBE is a B2BUA so the call legs are independent dialogs unaware of one another. What CUBE and the ITSP negotiate, such as session refresh, is independent of what CUBE and CUCM work out.

[Ayodeji Okanlawon]

In addition to what everyone has said, your focus is perhaps off track here. MIN-SE is just the lowest threshold acceptable for the call. Your session expire timer is actually what determines at what point the session will be refreshed by whoever the session refresher is. You should see a line like this in the 200 OK to the SIP INVITE request

"Session-Expires: 1800;refresher=uac" or

Session-Expires:  1800;refresher=uas

In this example you can see that if this was for an inbound call, CUBE should expect a RE-INVITE about 15 minutes into this call. If the refresher was set to "uas", then CUBE should send a RE-INVITE about 15 minutes into this call. 

The best way to know what is happening to session refresh is to turn on debugs at interval when you expect session refresh to happen.

For example, if your session-expire is set to 30 minutes, then do the following

1. Turn on debug ccsip message at the start of the call

2. Once call is established, turn it off

3. At about 13 minutes into the call, turn it on again

4. Wait for about 3 minutes and at this point your session refresh should have happened..

5. Stop debug and post here so we can see why session refresh is not happening

[Marcelo Morais]

Hi @Gordon Ross,
 just adding more info ... please take a look at the following link: SIP - Session Timer Support.
1. "... The Min-SE value can be set only by using the min-se command in the configuration gateway ..."

The min-se is a global parameter that negotiates per leg, you can check it by the show sip-ua min-se command.

2. "... The initial INVITE request establishes the duration of the session and may include a Session-Expires header and a Min-SE header. These headers indicate the session timer value required by the user agent client (UAC). A receiving user agent server (UAS) or proxy can lower the session timer value, but not lower than the value of the Min-SE header. If the session timer duration is lower than the configured minimum, the proxy or UAS can also send out a 422 response message ..."

Take a look at the following images (01 - 05.png).

Hope this helps,

 Marcelo Morais