Yealink Skype for Business HD IP Phones Administrator Guide378SIP Session Description Protocol (SDP) UsageSDP Headers Supportedv—Protocol version Yeso—Owner/creator and session identifier Yesa—Media attribute Yesc—Connection information Yesm—Media name and transport address Yess—Session name Yest—Active time YesAppendix E: SIP Call FlowsSIP uses six request methods:INVITE—Indicates a user is being invited to participate in a call session.ACK—Confirms that the client has received a final response to an INVITE request.BYE—Terminates a call and can be sent by either the caller or the callee.CANCEL—Cancels any pending searches but does not terminate a call that has already beenaccepted.OPTIONS—Queries the capabilities of servers.REGISTER—Registers the address listed in the To header field with a SIP server.The following types of responses are used by SIP and generated by the Skype for Businessphone or the SIP server:SIP 1xx—Informational ResponsesSIP 2xx—Successful ResponsesSIP 3xx—Redirection ResponsesSIP 4xx—Client Failure ResponsesSIP 5xx—Server Failure ResponsesSIP 6xx—Global Failure ResponsesSuccessful Call Setup and DisconnectThe following figure illustrates the scenario of a successful call. In this scenario, the two endusers are User A and User B. User A and User B are located at Yealink Skype for Business phones.
