Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones1068Step Action Descriptionresponse indicates that the user is beingalerted.F4180 Ringing—Proxy Server toUser AThe proxy server forwards the 180 Ringingresponse to User A. User A hears the ring-back tone indicating that User B is beingalerted.F5CANCEL—User A to Proxy Server User A sends a SIP CANCEL request to theproxy server after not receiving anappropriate response within the timeallocated in the INVITE request. The SIPCANCEL request indicates that User Awants to disconnect the call.F6CANCEL—Proxy Server to User B The proxy server forwards the SIP CANCELrequest to notify User B that User A wantsto disconnect the call.F7200 OK—User B to Proxy Server User B sends a SIP 200 OK response to theproxy server. The SIP 200 OK responseindicates that User B has received theCANCEL request.F8200 OK—Proxy Server to User A The proxy server forwards the SIP 200 OKresponse to notify User A that theCANCEL request has been processedsuccessfully.Successful Call Setup and Call HoldThe following figure illustrates a successful call setup and call hold. In this scenario, the two endusers are User A and User B. User A and User B are located at Yealink SIP IP phones.The call flow scenario is as follows:1. User A calls User B.2. User B answers the call.
