tion 3. Update location 4. Create Session Request 5. Create Session Response 6. Attach Accept 7. RRC Connection Reconfiguration 8. Initial Context Response 9. Attach Complete 10. Bearer Modification 11. IP traffic Figure 2.14 LTE attach and Default EPS Bearer establishment. longer capable of packet data communication. However, it can still receive Short Message Services (SMSs) via GPRS signaling [32]. Traditionally, mobile phones activated a PDP Context when they needed one. The activation of an application, such as a web browser, also triggered the activation of the PDP Context, and shutting down that application triggered the deactivation of the PDP Context. Some devices have also been able to support multiple concurrent PDP Contexts. For instance, often different services have had their own PDP Context. Thus, Internet access, or access to an operator service such as MMS have had their own PDP Contexts. However, modern smartphones usually open one PDP Context after starting, and keep it active most of the time. This benefits applications and users by optimizing away the time required to set up a PDP Context on demand. The EPS architecture was designed to be completely packet switched with no CS mode. Hence, it makes little sense in an EPS network to just attach to the network without service. Therefore, in the EPS networks, in the network attachment procedure also the packet data connection is activated. This is called Default EPS Bearer Establishment. A simplified version of the network attach procedure signaling with the Default EPS Bearer establishment is shown in Figure 2.14. (The packet data connection in LTE is called a 'bearer', and in GPRS a 'PDP Context'. The names are different, but conceptually they are very similar.) Deploying IPv6 in 3GPP Networks The LTE network attach and default EPS Bearer establishment procedure is performed as follows: 1. Attach Request is sent by the UE to the network to indicate that the UE wishes to get service from this network. 2. Authentication and security functions are