Specifically regarding session timer:
every UPDATE or reINVITE renegotiates the use/non-use of the timer and
the timer value. So you may start with it off, and later turn it on, or
start with it on and later turn it off. If you're not careful, you may
start with it on and inadvertently turn it off.
Having said that, the value of changing this mid-call is questionable.
The primary value of session-timer is for true proxies that record-route
and want some ongoing indication of the status of the session. It
doesn't do them much good unless it is there for the duration, since
they can't initiate a change on their own.
The UAC and UAS, and B2BUA intermediaries, don't need session timeer,
because they can initiate an UPDATE or reINVITE or other message any
time they are curious about the state of the session, without bothering
with session timer.
For the general case, there is nothing to prevent you from making
changes in Supported/Required options mid-dialog. The duration of
validity of these things is not well specified in any general way,
though it may be for some specific ones. In general you can only assume
they are valid for the duration of a single transaction.
Of course if you use Required mid-call you do potentially run the risk
of that *request* being rejected. But even then, that will not break
your dialog.
Thanks,
Paul
Balu Meenakshi-a24053 wrote:
> Hi All,
> How to implement the mid call supported/required option tag
> modification?
> For e.g. at the start of the call Session timer is not supported,
> mid-call I want to add this, is this allowed.
>
> Not only for session timer in general is it Ok to add/remove the
> supported/required option tags in
> mid call requests.
>
> Please comment on this.
>
> Thanks & Regards
> -Meena
>
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