# Integrating IP Mobility Management Protocols and MANET: A Survey
## 4 IP Mobility Management in MANET and Comparative Summary
### Hybrid Gateway Discovery-Based Mobility Management Solutions
Mobile nodes can issue and broadcast a route request with an agent multicast group address as the destination of the message in order to discover available foreign agents. Once a mobile node receives a route reply, it can then unicast a solicitation message to the foreign agent. The proposed system requires mobile nodes to register with a foreign agent to access the extended network. The registration procedure takes place after the agent advertisement is received, using a registration request and registration response message. Like MIPMANET, but with a few changes, the system uses a cell switching algorithm to manage mobility. A mobile node can register with a new foreign agent as long as it is two hops closer to the new foreign agent than the current one. The proposed system claims to piggyback routing information to the gateway advertisement messages, however the piggybacking procedure is not explained. _Mobility management in hybrid ad-hoc networks and the internet environment_[57; 58] proposed an architecture based on Mobile IP that consists of three layers; internet domains that contain home and foreign agents and corresponding nodes, mobile gateway nodes as the second layer, and MANET nodes as the third layer. The proposed architecture uses a distributed buffer management approach to provide reliable data delivery. Foreign agents are equipped with buffers to store traffic coming from the internet and the mobile gateway buffers are used to store MANET traffic that can be distributed later within the MANET or towards the foreign agents. The proposed architecture uses reactive and proactive gateway discovery, although there are no details about how the gateway discovery operates. It also uses a registration process to entitle a mobile node to register with a gateway node. The registration process takes a multi-layer registration approach. A mobile node initiates a registration request and sends it up the layer architecture to the gateway, then to the foreign agent, and finally to the initiator's home agent. The home agent creates the corresponding mobility binding and sends the registration confirmation down the architecture to the mobile node, which can then complete the registration with the gateway. The system supports handover between different gateways (micro mobility) and between different MANETs (macro mobility). It proposes three variant handover mechanisms: Mobility management with force handover, mobility management with optimized handover, and mobility management with prediction. The first is used if a mobile node loses its connection with its gateway. The second mechanism is used for handover where a mobile node finds a shorter route to another gateway and its route to its current gateway is still valid. The third mechanism combines prediction with the optimized handover. The handover decision is based on the shortest path and predicted gateway signal strength. _Mg-Aodv_[59] modifies Mobile IP and AODV to provide MANET-internet connectivity. The Mobile IP agent advertisement procedure was replaced by an AODV modified hello message. Some of the MANET nodes are set as gateways (foreign agents). They flood the network with modified hello message that contain a mobile gateway bit set to one. For registration, a mobile node should find a gateway to forward its registration request to its home agent. If no gateway is found, the mobile node has to broadcast a solicitation message to discover available gateways. Once it finds more than one gateway, the mobile node selects the appropriate gateway based on the hop distance and the payload of the gateway. The system also uses a different registration maintenance mechanism from that used in traditional Mobile IP. It uses a conditional registration renew mechanism according to which the renew procedure is only started when the route to the gateway is broken. The proposed system also modifies AODV to maintain two new tables. The first is maintained by a mobile gateway to store MANET nodes that have already sent solicitation or registration requests to this gateway.