Subject: [Sipping] Active call monitoring between UA's

From: Rajeev Narang <[email-masked]>
Date: Thu, 17 Feb 2005 20:19:36 +0530

Hi,

Say, we have a following configuration:-

UAC-----------Proxy1-----Proxy2----------UAS.

If we need to implement a mechanism at UA's for regularly monitoring the 
connection state (active or released) of the active calls established 
between UAC and UAS.
Say, if we detect by the monitoring mechanism that active call connection 
(either udp or tcp transport) to remote is failing, but somehow we didn't 
get a BYE, an appropriate action could be taken at UA for that particular call.

I think for a particular call the monitoring sequence should be running 
both sides to avoid any corner cases in sync error between two UA's. So it 
would be preferable to do the Request/Response sequence for monitoring the 
connection independently from each UA to its remote endpoint for a 
particular call.  Probably the sequence should be done after some random 
period every few minutes.

 From rfc3261, seems like using Re-INVITE or OPTIONS method are two 
choices. But there is no standard opinion on which is the best method to do 
it.

OPTIONS is described as a request to check on the capabilities of the 
server. How good will it be for doing the Request/Response sequence (both 
way) for connection monitoring.

Using ReINVITE would also require UA's to handle offer/answer during the 
Request/Response sequence. Probably need to take an action for RTP stream, 
if SDP is changed during ReINVITE. Also more message exchange is involved 
in this (INVITE/200/ACK) then OPTIONS.

Could you please suggest if for long term & backwards compatibility with 
existing implementation of SIP endpoints (3261 compliant) which choice is 
going to be better.

Thanks much,
Rajeev

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From: David Monahan <[email-masked]>
Date: Thu, 17 Feb 2005 15:30:35 +0000

Rajeev,

Does the sip session timer draft (draft-ietf-sip-session-timer-15.txt) 
provide the functionality you want?

Regards,
David

Rajeev Narang wrote:
> Say, if we detect by the monitoring mechanism that active call 
> connection (either udp or tcp transport) to remote is failing, but 
> somehow we didn't get a BYE, an appropriate action could be taken at UA 
> for that particular call.
> 
> both sides to avoid any corner cases in sync error between two UA's. So 
> it would be preferable to do the Request/Response sequence for 
> monitoring the connection independently from each UA to its remote 
> endpoint for a particular call.  Probably the sequence should be done 
> after some random period every few minutes.
> 
> choices. But there is no standard opinion on which is the best method to 
> do it.
> 
> server. How good will it be for doing the Request/Response sequence 
> (both way) for connection monitoring.
> 
> Request/Response sequence. Probably need to take an action for RTP 
> stream, if SDP is changed during ReINVITE. Also more message exchange is 
> involved in this (INVITE/200/ACK) then OPTIONS.
> 
> existing implementation of SIP endpoints (3261 compliant) which choice 
> is going to be better.
> 
> Thanks much,
> Rajeev
>

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From: Tom Taylor <[email-masked]>
Date: Thu, 17 Feb 2005 13:07:30 -0500

This was the intent of session timer (draft-ietf-sip-session-timer-15.txt).