User Manual

Yealink Skype for Business HD IP Phones Administrator Guide
394
SIP Session Description Protocol (SDP) Usage
SDP Headers
Supported
v—Protocol version
Yes
o—Owner/creator and session identifier
Yes
a—Media attribute
Yes
c—Connection information
Yes
m—Media name and transport address
Yes
s—Session name
Yes
t—Active time
Yes
Appendix E: SIP Call Flows
SIP 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 been
accepted.
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 Business
phone or the SIP server:
SIP 1xx—Informational Responses
SIP 2xx—Successful Responses
SIP 3xx—Redirection Responses
SIP 4xx—Client Failure Responses
SIP 5xx—Server Failure Responses
SIP 6xx—Global Failure Responses
Successful Call Setup and Disconnect
The following figure illustrates the scenario of a successful call. In this scenario, the two end
users are User A and User B. User A and User B are located at Yealink Skype for Business phones.