[SIPForum-discussion] difference between INFO and OPTIONS method?

[nidhi jain]

Hello, 

        CANCEL request is sent when response to INVITE message is not received. If 
this INVITE request is lost and UA may still send a CANCEL request. Is this 
possible? Can CANCEL request be sent without sending an INVITE message? 

        What is the basic difference between INFO and OPTIONS method? can OPTIONS 
used for mid-call signalling? 

        Why is ACK request required? Is it just to avoid retransmission of response 
message. This could be done even by starting the media transmission. 

        How are DTMF digits sent before the session setup? 

Please reply. 

Thank you. 

       
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