Which three SIP request methods are available?

2 thoughts on “Which three SIP request methods are available?”

1. SIP Requests:
   There are fourteen SIP Request methods of which the first six are the most basic request / method types:

   INVITE = Establishes a session.
   ACK = Confirms an INVITE request.
   BYE = Ends a session.
   CANCEL = Cancels establishing of a session.
   REGISTER = Communicates user location (host name, IP).
   OPTIONS = Communicates information about the capabilities of the calling and receiving SIP phones.
   PRACK = Provisional Acknowledgement.
   SUBSCRIBE = Subscribes for Notification from the notifier.
   NOTIFY = Notifies the subscriber of a new event.
   PUBLISH = Publishes an event to the Server.
   INFO = Sends mid session information.
   REFER = Asks the recipient to issue call transfer.
   MESSAGE = Transports Instant Messages.
   UPDATE = Modifies the state of a session.

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2. Correct

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