 across networks. The aim of mobility management is to track where the subscribers are, allowing calls, SMS and other mobile phone services to be delivered to them anywhere, E2E Network Architecture and Mobility Management anytime. There are several pieces attached to MM including - personal mobility, session mobility, and network and terminal mobility: Personal Mobility defines the ability of the user to access his/her personal services (for e.g., bookmarks, calendar, etc.) while away from the home network. Session Mobility is about maintaining seamlessness in sessions when moving from one network to another (e.g., movement from WiMAX to EV-DO, EV-DO to EPS, etc.). Network and Terminal Mobility defines the capability of both the network and the terminal to support roaming. 11.4.1 Mobility Management in 3GPP The UMTS networks employ the GPRS Tunneling Protocol (GTP) for the mobility management across its radio access networks. All packet sessions are transported or relocated through the GPRS tunnel by the GPRS Mobility Management (GMM) procedure according to the Packet Data Protocol (PDP) context [5]. The mobility management functionality is optimized for the UMTS networks to support both circuit-switched and packet-switched network architecture, but aimed mainly for the circuit-switched telephone service. However, the high signaling overhead is not efficient for packet switched services [6]. To overcome this challenge, 3GPP has introduced PMIP (Proxy Mobile IP) [7] for EPS which is highly effective in reducing the signaling cost for mobility management for various architecture options [6]. The S5 and S8 reference points in the EPC architecture have been defined to have both a GTP and PMIP variant. The GTP variant is documented in TS 23.401 while the PMIP variant is documented in TS 23.402. The mobility management process that will handle mobility between 3GPP and non-3GPP accesses should minimize the impact on legacy systems (i.e., UTRAN and GERAN). The operators can deploy single or multiple IP mobility mechani