Yealink SIP-T38G, Administrator'S Manual

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Administrator’s Guide for SIP-T3xG IP Phones
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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—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