Manoj Priyankara [TG] wrote:
> Dear All,
>
> According to the RFC 3261, SIP OPRIONS message should be used to query
> the statue of other UAC or the UAS. Is it OK to use the OPTIONS as a
> keep alive message to know whether the UAS is alive?
>
> Is it necessary to send the OPTIONS message from a registered user or is
> it possible to send the OPTIONS message from a general user and get 200-
> OK as the response?
Its not entirely clear what you want to determine by using OPTIONS.
Are you looking to verify the liveness of your peer UA in a dialog?
If not, what?
OPTIONS isn't a good choice for testing the peer in a dialog.
If you send it in-dialog (using the remote target, route set, call ID,
from and to tags of the dialog), then presumably it will follow the path
of dialog. But when it reaches the UAS, according to 3261 it is supposed
to treat the same as an OPTIONS received out of dialog. Its not entirely
clear what that means. It might mean that it could succeed even though
the UA has lost track of the dialog. (Consider for instance that the UA
has rebooted and lost all state.)
Because the handling is somewhat ambiguous in this case, you can't trust
the results to report what you want to know.
To test the liveness of your peer in an invite dialog you are better off
to use reINVITE or UPDATE.
Thanks,
Paul
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