Yealink SIP-T21 E2

Appendix
1061
6xx Response
Supported
Notes
603 Decline
Yes
604 Does Not Exist Anywhere
No
606 Not Acceptable
No
SIP Session Description Protocol (SDP) Usage
SDP Headers
Supported
v—Session Description Protocol Version
Yes
o—Owner/Creator, Session Id
Yes
a—Media Attribute
Yes
c—Connection Information
Yes
b—Bandwidth Information
Yes
m—Media Description, name and
address
Yes
s—Session Name
Yes
t—Time Description, active time
Yes
Appendix I: 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 IP phone or the SIP
server:
SIP 1xx—Provisional Responses
SIP 2xx—Successful Responses
SIP 3xx—Redirection Responses
SIP 4xx—Request Failure Responses