Hello! We have found that enabling 100rel in Linksys phones break call proceeding with our equipment. Our Nokia-Siemens hiQ4200 support PRACK and supporting of this messages prerequisite for some services provided. The reason is Linksys don't authenticate PRACK (9th packet in callflow bellow):
195.162.99.99 (Linksys) 195.162.59.99 (NSN) 1 : |U------------INVITE----------->| 2 : |<------100 Trying/INVITE------U| 3 : |<---401 Unauthorized/INVITE---U| 4 : |U-------------ACK------------->| 5 : |U------------INVITE----------->| 6 : |<------100 Trying/INVITE------U| 7 : |<-183 Session Progress/INVITE-U| 8 : |U------------PRACK------------>| 9 : |<----401 Unauthorized/PRACK---U| 10: |U--------audio/PCMU(0)-------->| 11: |<-183 Session Progress/INVITE-U| 12: |<-183 Session Progress/INVITE-U| 13: |<-183 Session Progress/INVITE-U| 14: |<-183 Session Progress/INVITE-U| 15: |U------------CANCEL----------->| 16: |<--------200 OK/CANCEL--------U| 17: |<-487 Request Terminated/INVI-U| 18: |U-------------ACK------------->| We have contact Linksys support and they answer that call proceeding broken because NSN softswitch mark PRACK as Required and UAS reply with 100 Trying on initial INVITE. Which side is right in this situation? Should Linksys send authenticated PRACK or softswitch shouldn't send 100 Trying? Response from Linksys: ----------------------------------- RFC 3262 - Regarding to PRACK works as describe The UAC (in this case the Linksys) "If the UAC does not wish to insist on usage of reliable provisional responses, but merely indicate that it supports them if the UAS needs to send one, a Supported header MUST be included in the request with the option tag 100rel. The UAC SHOULD include this in all INVITE requests." - The Linksys INVITE shows the option as not insisting on it. More about the RFC3262 "If a provisional response is received for an initial request, and that response contains a Require header field containing the option tag 100rel, the response is to be sent reliably. If the response is a 100 (Trying) (as opposed to 101 to 199), this option tag MUST be ignored, and the procedures below MUST NOT be used." - And the UAS reply with the 100 trying then our SPA would ignore the next command waiting the regular 180 ringing or the 200 ok. -- Best regards, Igor Goncharovsky _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
