2009/2/4 Avasarala Ranjit-A20990 <[email protected]>:
> Yes, Contact header is required for all SIP Messages.

Not at all. Contact is just required for requests creating a dialog
(INVITE, SUBSCRIBE) for registering a contact (REGISTER), for 3XX
replies, for 2XX replies to a request creating a dialog (INVITE,
SUBSCRIBE), 2XX from a registrar.

There is also some confusion about the requeriment (or not) of Contact
in a 1XX response (for an INVITE). If a 1XX (non 100) has no Contact
then in-dialog messages (even if early dialog) from UAC to UAS
wouldn't be possible (INFO, PRACK...).

Regards.


-- 
Iñaki Baz Castillo
<[email protected]>

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