Hi Abhishek, Can you elaborate more for three way handshakes and which part of three way handshakes you think is not required?
100 Trying can be generated even for Re-INVITE if the processing of the same is going to take more than 200ms. I don't think there is any such restriction in RFC for this. I think generating 100 trying for non INVITE request is not recommended but still can be generated, depending upon implementation at UAC. Please note that 100 Trying is mainly to inform the originating Endpoint that the request is received by either the proxy or destination endpoint depending upon how request is forwarded. Regards Sunil Verma -----Original Message----- From: sip-implementors-boun...@lists.cs.columbia.edu [mailto:sip-implementors-boun...@lists.cs.columbia.edu] On Behalf Of abhishek chattopadhyay Sent: Wednesday, September 22, 2010 4:48 PM To: sip-implementors@lists.cs.columbia.edu Subject: [Sip-implementors] why Do we need a 3 way handshake for INVITE atall? Importance: High Hi Implementors, In 3261 the re-transmission of INVITE is stopped by 1xx responses. So to stop the re-trnasmission of 200 OK, ACK is sent. (Albait it would be worth considering that ACK is used for a lot of other purposes.) Further form 3261 only, it is clear that for other methods the request would be re-transmitted till a 200 is received. The entity sending a 200 OK would understand that the 200 has been successfully received if the Method is not re-transmitted again. My question is, Why at all a 3 way handshake is implimented for INVITE. And 100 trying is not restricted for any Method inside a dialog, so if a 100 Trying is issued for say UPDATE then why it is not the same case as of the Re-INVITE's arriving inside the same dialog. Thanks Abhishek. _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
