Chapter 4 FortiOS Carrier : GTP identity filtering : Other identity and location based information elements : Access Point Number (APN) : Routing Area Identifier (RAI)
  
Routing Area Identifier (RAI)
Routing Areas (RAs) divide the carrier network and each has its own identifier (RAI). When a mobile device moves from one routing area to another, the connection is handled by a different part of the network. There are normally multiple cells in a routing area. There is only one SSGN per routing area. The RAI and ULI are commonly used to determine a user’s location.
RAI is part of advanced filtering configuration. See “Configuring advanced filtering in FortiOS Carrier”.