# Tunnel-Free Distributed Mobility Management (DMM) Support Protocol for Future Mobile Networks
## 2 Proposed Tunnel-Free DMM Support Protocol
### Overview  
At an access network level, the proposed DMM approach depends on distributed mobility anchors as follows:  
* _Base Mobility Agent (BMA):_ The HA of MIPv6 is expanded to a BMA. The BMA performs mobility and routing management for the MN. The network prefix is assigned to the MN by BMA. The MN is supplied by the BMA it is currently attached to. The architecture is distributed, and therefore multiple BMAs are deployed. For a MN on the move, it gets attached to another BMA in its range when it is about to leave the coverage area of the previous BMA. In this design, session continuity of a MN on the move is ensured by using the MBB approach. In traditional break-before-make infrastructures, only one connection can exist between a node and an access point. This requires nodes to continually break and re-establish connectivity as they move between access points. By using the incrementally evolved MBB [23; 24] approach, a network can scan for and determine the next best available path prior to handoff. User data packets that go to and from the BMA and MN are transferred within a radio access network where the MN is currently connected. The handover control within the domain is focused on accommodating user mobility, while at the same time avoids interrupting or delaying ongoing user packets transfer, degrading the QoS of such a user packet transfer, or dropping user packets that should not be dropped. Therefore, the MBB approach is adopted, i.e., network resources at the target side are reserved prior to the movement of a MN to the target cell. Mechanisms used to reserve resources at the target side are carefully designed to ensure the success of the handover. During handover, BMAs may be relocated due to old BMAs that could not serve the MN. The handover takes place when the MN is in the overlapping region of the two BMAs. Connections can be established to the two BMAs simultaneously, and in this manner, the MN can communicate with two BMAs. The availability of more than one active connection through the handover process leads to a more seamless and reliable handover performance. The adjacent cells work on similar channels or frequencies that MBB uses for simultaneous connections, thus the MNs can communicate simultaneously with the old and new BMAs during the handover. Once the handover with MBB is complete, the new BMA informs the Corresponding Node (CN) about the MN's updated path and the connection to the previous BMA is dropped. Once the MN is attached to the new BMA, a new address is assigned to it. If the MN has an unfinished, ongoing transmission session with the previous address, the previous address is maintained by the MN until the new address is completely configured. When the new address is completely configured, an IP handover takes place. The previous ongoing session is then continued on the newly configured address. The previous address is then discarded by the MN. The previous session, as well as the new session, will now be anchored through the new BMA. Signaling Messages: There will be two separate signaling messages. * _Binding Update (BU) and Binding Acknowledgment (BA):_ The MN registers its movement to the current BMA through a BU message. The MN sends the BU message containing the new address configured at the current BMA and the previous address configured at the previous BMA. The current BMA then sends a binding acknowledgement (BA) message to notify the MN of the success or failure of its registration for each address. * _New Binding Update (NBU) and New Binding Acknowledgment (NBAck):_ The purpose of the NBU message is to update the MN's mobility status from the previous BMA to the current BMA and to continue the previous ongoing session with the newly configured address. It should be noted that the NBU message is sent once the current BMA validates that the previous session has been linked to the new address. In response, a NBAck message is sent to the previous BMA from the current BMA. The BMAs communicate with each other with the help of NBU and NBAck messages.