dynamically updating GTP tunnels within the PS domain. It may optionally communi- cate with the HLR (Home Location Register) via the Gc interface. It may provide OAM Next Generation Mobile Communications Ecosystem (Operations, Administration, and Maintenance) functionality and it also collects charging information related to external networks usage by the user. DNS/DHCP: DNS server is used to translate host names into IP addresses, that is, logical names are used instead of raw IP addresses. A DHCP server is used to manage the allo- cation of IP configuration information, by automatically assigning IP addresses to systems configured to use DHCP. Firewalls: Firewalls are used to protect service providers' backbone data networks from external attacks. The security is usually addressed by applying filtering mechanisms based on Access Control Lists (ACLs). Common Entities HLR: HLR is a subscriber database that holds each customer's unique profile. The profile includes international mobile subscriber identity (IMSI), and international mobile equip- ment identifier (IMEI), local and long distance carriers, calling package, calling restrictions, service rates, data package, and SO on. The MSC uses this profile to authorize system access and process individual call billing. EIR: The EIR (Equipment Identity Register) is a database that contains the identity of telecommunications devices (such as mobile terminals, data cards) and the status of these devices in the network (such as authorized or not authorized). AUC: The AUC (Authentication Center) stores and processes information that is required to validate the identity of the device. During the authentication procedure, the AUC processes information (such as IMSI, secret keys, etc.) along with a random number that is used by the device to produce an authentication response. The AUC compares its authentication response with device authentication response, and if it matches then the device is allowed access to the network. 8.2.1.2 Release 4 Release 4 supports two new radio