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AT - Authorization Token

The term AT is used in a number of scenarios in order to support authorized access to a resource or network services. In particular, AT are used in the SBLP (Service Based Local Policy) architecture of the Release 5 3GPP IMS (IP Multimedia Subsystem) specifications. Here, the AT is passed from the P-CSCF (Proxy Call Session Control Function) to the IMS terminal which is making a request for a service. The IMS terminal can then use the AT in its request for network resources when it signals its IP-CAN (IP Connectivity Access Network).


  • Fully interactive 3GPP based network map
  • Narrated call flows
  • Detailed network procedures

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