gaurav wrote:
> Hi All,
>
> I have following doubts regaridng the Call Hold implementation in SIP/SDP:
First, you must understand that SIP doesn't actually have a way to
signal Call Hold. What it has is a way to signal changes in the handling
of media that may be useful to a UAC implementing a call hold feature.
The difference is that the signaling thats useful for call hold is also
useful for other things as well. The UAS has no way to be certain that
the UAC is specifying the start of a hold, or something else that uses
the same mechanisms.
> 1.. What is the behavior of UAC and UAS in case the Call Hold using
> Re-Invite.
The usual approach is to send an offer with a=sendonly, to which the
answer is normally a=recvonly. Another possibility is to offer
a=inactive, to which the response should also be a=inactive.
An older approach is to offer c=0.0.0.0.
> 2.. How can UAS reject the Call Hold request, as the control of the call
> hold is with the UAC.
You can't reject call hold because it isn't signaled. (See above.)
I don't believe there is a valid way to reject a=sendonly or a=recvonly
either. If you understand them, then to be compliant you must respond in
a compatible way.
You could pretend not to understand, and just not return a matching a=
line for the a=sendonly. But I don't recommend that.
I don't understand why you want to do this. If the other side doesn't
want you to send it stuff, you can' force it to do so. At best you might
still be able to send media, but the other end will be ignoring it. If
the user on the other side has pushed the HOLD button on the phone, what
do you want to happen? Do you want the button to pop back up?
> 3.. If UAS rejects with 488 Not Acceptable Here, then what should be the
> ideal behavior of UAC, if it still want the call to be put on Hold.
If you are lucky, it will try to cope. It could try an alternative
mechanism, such as offering c=0.0.0.0, or it might just send your media
to the bit bucket. But it also may decide that you are a problem and
just send you a BYE.
> 4.. Can a reuqest to put the call on hold be rejected by UAS, if yes, then
> what is the call Flow.
> We are testing the Call Hold Flow through eBean Soft Phone and we are
> rejecting the request to put the call on hold by 488 to re-invite request,
> but the eBean Soft phone is not releasing the call hold when it receives the
> 488 response to re-invite.
>
> Where could be the problem? Please help in understanding the porblem and
> arriving at a solution.
Stop trying to prevent the other end from doing what it wants to do.
Paul
> regards
> Gaurav
> _______________________________________________
> Sip-implementors mailing list
> [email protected]
> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>
_______________________________________________
Sip-implementors mailing list
[email protected]
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
