Secure Roaming in 802.11 Networks

Chapter 2

covered in earlier sections of this chapter. The service area supported by each SGSN is sub-

divided into Routing Areas (RAs) that are analogous to the service areas in GSM. When the

MS moves from one RA into another, the MS performs a routing area update similar to a

location update in GSM. However, unlike location updates, the RA updates can be performed

during a data session, also called a Packet Data Protocol context or PDP context. In GSM, the

MS cannot transmit control signals until a call has ended, but in GPRS control signals can be

sent between data packets [7]. The interface between SGSNs primarily exists to facilitate

forwarding ...