n outside its MSC, the VLR in this new location queries the HLR and gets information about the subscriber to avoid querying the HLR each time the user wants to access a service. The user in the new location is called a visiting subscriber. Additional functional elements in GSM include: Authentication center (AuC): Handles security using authentication and encryption. - Equipment identity register (EIR): Database to store the identity of mobile equipments to prevent calls from unauthorized equipments. Gateway mobile switching center (GMSC): A gateway integrated with MSC to interconnect two networks. It can be used for routing calls from a PSTN (public switched telephone network) to a GSM user. There can be many more components like message center (MXE), mobile service node (MSN), and GSM inter-working unit (GIWU) that can be seen in a GSM network. Some definitions specify operation and support system (OSS) as a part of GSM, though it is a more generic term that applies to operation and support for any kind of network. From telecom management perspective, 3GPP lists a detailed set of specifica- tions on operation, administration, and maintenance of GSM networks. The fault parameters and the performance attributes for network management of GSM net- work is given by 3GPP specifications. It should be noted that a telecom manage- ment solution for GSM network does not necessarily mean management of all components in a GSM network. There are element management solutions that spe- cifically deal with MSCs, BSCs, or HLRs and network management solutions that only handle the core network in GSM. 9.4 GPRS Network The general packet radio service (GPRS) network is more of an upgrade to the GSM network. The same components of the GSM network provides voice service and the GPRS network handles data. Due to this reason the GSM network providers do not have to start from scratch to deploy GPRS. GPRS triggered the transformation from circuit switched GSM network to packet switched network and hence is con- sidered a technology be