[SIPForum-discussion] Different cases/conditions for SIP re-invite

[Kevin P. Fleming]

On 09/19/2010 08:54 PM, amit salunkhe wrote:

> I want to know what are the different cases or conditions at which
> SBC,SIP proxy or UA can generate SIP re-invite. Like when A calls B & B
> put call on hold which send reinivite to A, i require such cases.

What you are asking for is impossible: the number of cases that could
generate a re-INVITE is (probably) nearly infinite. Here are a small
number of examples:

* UA wants to change media formats for a stream
* UA wants to change status of stream between sendrecv, sendonly,
recvonly, inactive
* UA wants to add/remove stream(s)
* UA wants to redirect media to a different location (IP address/port)
* UA wants to change Remote-Party-ID/P-Asserted-Identity information
* UA is using Session-Timer support and wants to refresh the session

> Also for long duration call if there was no significant Media packet
> flow, Can SIP proxy or SBC send SIP reinvite to chcek the call status on
> A party side as well as B party side & if there was no response on that
> on that renivite,sbc will disconnect that call?
>  
> can we say SIP re-invite as session refresher message?

Yes; this is called "Session-Timer" support, and it's documented in an RFC.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kfleming at digium.com
Check us out at www.digium.com & www.asterisk.org