Hi,

In RFC 3261

Contact                1xx           -   -   -   o   -   -
Contact                2xx           -   -   -   m   o   o

For there i guess it's optional, but no the case:

UA1 -> UA2
UA2 sends ringing without Contact
UA1 created early dialog, but wants to terminate it, it must send BYE
...... no contact header what should do ?

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