Hi Udit Pls refer Section 9.1 Client Behavior of RFC 3261
"Once the CANCEL is constructed, the client SHOULD check whether it has received any response (provisional or final) for the request being cancelled (herein referred to as the "original request"). If no provisional response has been received, the CANCEL request MUST NOT be sent; rather, the client MUST wait for the arrival of a provisional response before sending the request. If the original request has generated a final response, the CANCEL SHOULD NOT be sent, as it is an effective no-op, since CANCEL has no effect on requests that have already generated a final response. When the client decides to send the CANCEL, it creates a client transaction for the CANCEL and passes it the CANCEL request along with the destination address, port, and transport. The destination address, port, and transport for the CANCEL MUST be identical to those used to send the original request." Regards, Tarun ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, October 21, 2008 11:33 AM To: [EMAIL PROTECTED]; [email protected] Subject: [Sip] Sip query - 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 ? CONFIDENTIALITY NOTICE: This e-mail message, including any attachments, is being sent by 3Com for the sole use of the intended recipient(s) and may contain confidential, proprietary and/or privileged information. Any unauthorized review, use, disclosure and/or distribution by any recipient is prohibited. If you are not the intended recipient, please delete and/or destroy all copies of this message regardless of form and any included attachments and notify 3Com immediately by contacting the sender via reply e-mail or forwarding to 3Com at [EMAIL PROTECTED] ________________________________ "DISCLAIMER: This message is proprietary to Aricent and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error,please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. Aricent accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus."
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