eNodeB 1. Attach Request 2. Authentication and Authorization 3. Update location 4. Create Session 4b. Proxy Binding Request Update 5. Create Session 5b. Proxy Binding Response Acknowledgement 7. RRC Connection 6. Attach Accept Reconfiguration 8. Initial Context Response 9. Attach Complete 10. Bearer Modification 11. IP traffic Figure 2.18 LTE attach and Default EPS Bearer establishment in PMIP-based architecture. Deploying IPv6 in 3GPP Networks GTP-U GTP-U UDP/IP UDP/IP LTE-Uu S5/S8 eNodeB Figure 2.19 EPS user-plane protocols in PMIP architecture variant. In addition to the technical differences of the two architecture variants, there is a difference between the protocol approaches of PMIP and GTP. The tradition in protocol design in the IETF is a little different from that in 3GPP. This is also visible when comparing the GTP to the PMIP. 3GPP has a tradition of specifing a single protocol to cover a protocol layer over one interface. Originally, GTP was designed for the Gn/Gp- interface to cover both control and user plane. PMIP, on the other hand, was designed as a protocol to provide network based mobility management. However, the IETF already had different generic tunneling protocols available, and PMIP can use many of those. 3GPP decided to use the GRE option because, with some extensions [39], it could basically support the same use cases as GTP did. The original idea of the PMIP-based EPS architecture was to be simpler, better com- patible with the IP and IETF concepts, and facilitate better interworking to other cellular wireless technologies such as technologies standardized by 3rd Generation Partnership Project 2 (3GPP2 [40] or the WIMAX Forum [41]. However, in the end, the PMIP technology was enhanced to support practically the same use cases as the GTP was [39, 42, 43]. In addition, at the time of writing, PMIP has had limited success in inter- working to other mobile networking technologies. As of today, most EPS deployments use the GTP variant, though some PMIP based deployments do exist as well. 2.