Sip query

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A query on Sip call flow -

Party sends out INVITE with SDP info to party B to make a call. 
Party B receives the message and sends back 183 Session progress with SDP 
info to party A. In the 183 message, it does have Contact information.
Now, party A sends out CANCEL message to party B using contact header 
information received in 183 message.

Will it be valid in SIP to use Contact information before receiving 200 OK 
message or not ?

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