Distributed mobility management for future 5G networks: overview and analysis of existing approaches <s> INTRODUCTION <s> Network-based mobility management enables IP mobility for a host ::: without requiring its participation in any mobility-related signaling. ::: The network is responsible for managing IP mobility on behalf of the ::: host. The mobility entities in the network are responsible for ::: tracking the movements of the host and initiating the required ::: mobility signaling on its behalf. This specification describes a ::: network-based mobility management protocol and is referred to as Proxy ::: Mobile IPv6. [STANDARDS-TRACK] <s> BIB001 </s> Distributed mobility management for future 5G networks: overview and analysis of existing approaches <s> INTRODUCTION <s> This document defines the requirements for Distributed Mobility ::: Management (DMM) at the network layer. The hierarchical structure in ::: traditional wireless networks has led primarily to centrally deployed ::: mobility anchors. As some wireless networks are evolving away from the ::: hierarchical structure, it can be useful to have a distributed model ::: for mobility management in which traffic does not need to traverse ::: centrally deployed mobility anchors far from the optimal route. The ::: motivation and the problems addressed by each requirement are also ::: described. <s> BIB002
In the recent years, Internet data communications have experienced a paradigm shift from the traditional fixed cable access to the wireless and mobile world. The huge success of powerful handheld devices and the deployment of faster heterogeneous radio access technologies, like IEEE 802.11n and Long Term Evolution (LTE), have led to the familiar concept of being connected anywhere, anytime. Reports such as  show that mobile traffic growth will not decelerate; conversely, it will increase 11-fold from 2013 to the end of 2018. Mobile operators, together with industry and research communities, are looking at cheap and effective solutions to cope with this tremendous growth. There are two main issues to tackle: • How to provide enough capacity in the access • How to handle all the traffic in the transport network For the first issue, reducing the size of cells is the most feasible approach that can provide a significant bandwidth increase. Regarding the second issue, current architectures for mobile and cellular networks are highly centralized and hierarchical, forcing user traffic to traverse all the network parts up to the core, where key entities are deployed to function as border IP gateways and mobility anchors. Following this approach, the general packet radio service (GPRS) Tunneling Protocol (GTP)  and Proxy Mobile IPv6 (PMIPv6) BIB001 have been adopted as two possible choices to operate the Evolved Packet Core (EPC) of 4G networks. The advantage of the centralized approach resides in its simplicity, because the central anchor can follow user movements by simply rerouting the packets over tunnels created with the access router where the mobile node (MN) is currently connected. However, the mobility anchor represents a single point of failure, poses scalability issues (i.e., it is the cardinal point for the control and data plane for millions of users), and, in general, leads to suboptimal paths between MNs and their communication peers (also known as correspondent nodes, CNs) BIB002 . Therefore, future 5G mobile networks are expected to be more flexible, relaxing the constraint of binding user traffic to a central core entity and allowing Internet services to be located closer to the users. Extremely dense wireless deployments shall benefit from such features by reducing the congestion in the operator's core infrastructure and providing improved service to users. Another defining characteristic of future 5G networks is that the infrastructure is expected to simultaneously serve very different sets of users and applications. For example, 5G networks are foreseen to share resources to cope with both highly demanding video applications of a few mobile users and low-bit-rate traffic from a large bunch of sensors (the so-called Internet of Things, IoT). Along with these objectives, distributed mobility management (DMM) has recently emerged as a new paradigm to