ns to networks other than the already ongoing connection. Hence, connections have their own Basics of the 3GPP Technologies PDP Context Network A PDP Context Network B EPS Bearer Network A eNodeB EPS Bearer Network B Figure 2.22 Multiple connections to different PDNs. IP addresses from other IP-networks than the original connection. This can be useful, for instance, when the UE needs to be connected at the same time to the Internet, and to some operator-provided services that are not available through the public Internet. In order to create a new connection to a new IP-network, the UE will perform either Primary PDP Context activation as described in Figure 2.13, or a new default EPS Bearer activation as shown in Figure 2.16. The selection of the gateway that leads to the desired PDN is done by providing the Access Point Names (APNs) during the activation sequence. We will look at the APN in Section 2.5.2. Figure 2.22 depicts the multiple PDN concept. 2.5.2 Access Point Name As described in Section 2.5.1, the selection as to which external network the UE will be connected is based on the APN [45]. An APN is an identifier, which points to an external network or service. The APN has two parts - the Network Identifier, and the Operator Identifier. The Network Identifier uniquely identifies the network to which a GGSN or PGW is connected, or the service it provides. The Operator Identifier defines in which operator's network that GGSN or PGW is located. The overall structure of the APN follows the Domain Name System (DNS) format [46-48]. However, the operator identifier also has its own specified format. The format is mnc<MNC> mcc<MCC> gprs. Where the Deploying IPv6 in 3GPP Networks MNC is the three-digit Mobile Network Code, and the MCC is the three-digit Mobile Country Code. Here are a couple of examples of what an APN looks like: province1.mnc012.mcc345.gprs ggsn-cluster-A.provinceB.mnc012.mcc345.gprs internet.apn.epc.mnc015.mcc234.3gppnetwork.org The DNS names resulting from the APN name format are used in the ne