On 3/8/12 8:32 AM, Kevin P. Fleming wrote:
> On 03/07/2012 07:01 PM, Sajeewa Don wrote:
>> I would like to understand different possible SIP REINVITE Scenarios.
>>> From my knowledge there are three occasions where reinvite could occur,
>>
>> Scenario 1 - To make a Call On Hold by sending a reinvite with
>> sendonly/recieveonly
>> Scenario 2 - To change parameters of the original connecting information
>> Scenario 3 - Allows periodic refresh of the SIP sessions through re-INVITE
>>
>> Is there any other possibile Reinvite scenarios?
>>
>> If you could share your knowledge on this that would be great.
>
> There are probably an infinite number of scenarios in which a re-INVITE
> could be issued. What do you believe is the value of trying to identify
> all possible reasons that you might receive a re-INVITE?
I agree.
To the original poster:
Is the goal to for the UAS to figure out *why* a particular reinvite was
sent?
That is a fools errand. You in general can't, and shouldn't try to,
know. Your behavior to a reinvite should not be based on knowing *why*,
it should simply respond to what is being proposed, in the context of
your current knowledge of your own state and policies.
For instance, a reinvite w/sendonly is not necessarily an indication
that the other end is putting the call on hold. All you know is that you
aren't allowed to send media to it. Also, once there is more than one
m-line in the call (e.g. audio & video) then they may have inconsistent
selections for sendrecv/..., so its hard to classify the call itself as
held or not. (I suggest you look at RFC6337. Take special note of
section 5.)
Also, every reinvite, whatever else it changes or does not change,
serves as a reset or refresh of session timer. This is true whether it
is periodic or not.
And don't forget reinvites with no offer. You need to support them too,
in spite of now having a clue of why you received it.
Good Luck,
Paul
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