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Intro

MAD-PMIPv6 is a network-based DMM solution for IP Mobility that inherits most of its features from Proxy Mobile IPv6 (see the IETF RFC 5213).

In a typical PMIPv6 domain, the data traffic generated by the users is conveyed from an access node called Mobility Access Gateway (MAG), acting as access router, to a core entity named Local Mobility Anchor (LMA), acting as linking point between the mobile network and the rest of IP networks. The LMA forwards the user's data packets to and from the access network by means of an IP tunnel between the LMA itself and the MAG where the user is currently connected.  When a mobile user moves and connects to another MAG, the LMA updates the IP tunnel accordingly, following the user movement. In this way, the LMA anchors the user's IP flows, regardless of the Mobile Node (MN) location changes. The routing status is coordinated through signaling between the LMA and the MAG using Proxy Binding Update and Proxy Binding Acknowledgment messages.

PMIPv6 architecture: the LMA connects the PMIP domain with the rest of IP networks. Data traffic is tunneled when it traverses the domain, i.e., between the LMA and MAGs.

MAD-PMIPv6 evolves from PMIPv6 by relocating the data anchoring function from the LMA to the MAG. This new MAG, renamed into Mobility Anchor Router (MAR), is responsible to anchor the IP flows started when the MN is connected to it, without relying on a centralized node. Therefore, the data path does not traverse the core network, avoiding unnecessary overhead due to the sub-optimal path that the core network traversal might introduce. Thus, tunneling is not needed as long as the user is static. On the contrary, if the MN changes point of attachment, a tunnel is established between the current MAR and the one where the active IP flows were started. If the there are no IP flows to be preserved after a movement, the mobility procedure is not required. However, new IP flows are treated as if the MN were static, that is, they are not encapsulated in a tunnel. In general, if a MN visits multiple access networks, it maintains flows anchored at multiple MARs. This enables a better distribution of the IP flows, relieving most of the burden from the central entity.

Nevertheless, a reduced LMA is maintained in MAD-PMIPv6, with the unique role of managing the mobility bindings, as a centralided database quieried by the MARs in order to sychronize the status of the users in the domain. This node is called Central Mobility Database (CMD).

MAD-PMIPv6 architecture: MARs are directly connected to the rest of IP Networks, without traversing other gateways. Data traffic is tunneled only for those IP flows started at a different MAR.