Provisional responses (typically 18x) without using PRACK are not reliable.
So if the 18x is carrying SDP information then if the 18x didn't get through then early media (which could contain an important announcement) would fail. PRACK makes sure that the 18x is reliable. The 18x gets sent and then the sender waits for a PRACK request. If, after a while the PRACK isn't received, the 18x is retransmitted. The retransmissions of the 18x message try to make sure that the early media succeeds. Regards, Attila -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Nithyakumar.R Sent: 09 December 2006 08:00 To: [email protected] Subject: [Sip-implementors] PRACK Doubt Hi, What was the use of PRACK??? ..In what situation this msg will be used..Please clear my doubt. With Regards, Nithyakumar.R This e-mail and attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient's) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
