. The routing area identity is given as RACxxxx.LACyyyy.MNCzzzz.MCCwwww.GPRS where x,y,z and W are decimal coded digits. RAC, LAC, MNC and MCC are coded as decimal numbers with leading zeros if necessary. The length is always 4 digits. Both hardware and software are required for DNS operation. The software used in DNS equipment is called BIND, or Berkeley Internet name domain. Gn Interface in WAN Though the WAN interface is used for the Gi and Gp interfaces, it can also be used for the Gn interface in cases where the SGSN and GGSN are remote and not co-located. Planning of the Gn interface for WAN is based on topology, connectivity and traffic estimates. The Gn network can be extended between sites by using the routed or bridged WAN, with the major difference being the layer 2 Gn LAN at each site, with a discrete routed subnetwork in the former while in the latter it is extended to multiple sites. Routing in Gn The OSPF is the routing protocol in the Gn network. Routing can be both static and dynamic. Static routes are unsuitable for fallible networks while dynamic routes are determined by groups of routers sharing information. Routes can be manually defined in the router (static routes) and can be changed only by the administrator. This scheme of things is used where there are small numbers of subnets and routes or the topology is unchanged. Dynamic routing is used where there are large numbers of subnets and routes or the topology changes frequently. 4.13.4 Gi Interface Planning The packet core network is connected to the external IP networks via the Gi interface. The external networks are mainly of three types: Internet, Intranet and Extranet. The Internet is a global network Mobile Packet Core Architecture Planning of computers, which operates using a common set of communications protocols. The Intranet is an interconnected network within one organisation that uses Web technologies to share information inter- nally, not worldwide. An Extranet can be viewed as part of a company's Intranet but is extended to us