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CT Cloud SIP - Signaling Basics


Below will offer you insight into the basics of SIP signaling.


SIP is establishing sessions between two or more telecommunications devices over the Internet.


SIP Headers:

  • INVITE :Invites a user to a call
  • ACK : Acknowledgement is used to facilitate reliable message exchange for INVITEs.
  • BYE :Terminates a connection between users
  • CANCEL :Terminates a request, or search, for a user. It is used if a client sends an INVITE and then changes its decision to call the recipient.
  • OPTIONS :Solicits information about a server's capabilities.
  • REGISTER :Registers a user's current location
  • INFO :Used for mid-session signaling



SIP Errors:

  • 1xx: Provisional -- request received, continuing to process the request;
  • 2xx: Success -- the action was successfully received, understood, and accepted;
  • 3xx: Redirection -- further action needs to be taken in order to complete the request;
  • 4xx: Client Error -- the request contains bad syntax or cannot be fulfilled at this server;
  • 5xx: Server Error -- the server failed to fulfill an apparently valid request;
  • 6xx: Global Failure -- the request cannot be fulfilled at any server.
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