# 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
So, a mobile node that is within n hops of a gateway can be served by this gateway. If a mobile node is within the service scope for more than a gateway, it selects its gateway based on the shortest path criteria. It also introduces another parameter called M, associated with each DSDV node to define the maximum distance to which a node can forward traffic. If the traffic needs to be forwarded to a destination that is greater than M, the traffic must go through the internet. The proposed system uses Mobile IP registration for mobility management. A mobile node that moves to the scope of another gateway would register with the new gateway and its traffic will be tunneled by its previous gateway to the new one. However, the use of a defined parameter to form the scope of a gateway can be seen as limitation of this system since the proposed system does not prevent a mobile node from rebroadcasting the same advertisement message many times. The actual scope of a gateway will therefore not be met. Furthermore, the relay of MANET traffic using the external network is a drawback of the system, where more burden is placed on the gateway. _A hybrid approach to internet connectivity for mobile ad hoc networks_[48] provides internet connectivity and node mobility management for internet-MANET integrated networks using Mobile IP and AODV. Foreign agents were used to relay traffic between MANET nodes and their corresponding node on the internet. Similar to [PERSON] [55], the proposed system is based on limiting the propagation of agent advertisement messages to avoid flooding the network with Mobile IP excessive control overheads. It is claimed that the limited broadcasting of agent advertisement message contributes to reducing control overhead where a reduced number of solicitation messages would be sent by MANET nodes. For determining whether a destination is in the MANET or external, the proposed system uses foreign agent route reply message FA-REP to reply to any received route request from  
Figure 12: Integrating mobile IP with ad hoc networks [55]. MANET when a foreign agent happens to have no route to it. The FA-RREP will be understood by the initiator as a non-local destination that is on the internet. A mobile node is required to register periodically with a foreign agent to maintain up-to-date route entry to a gateway using the broadcast agent advertisement messages. However, far-away mobile nodes from foreign agents will not receive the agent advertisement message as the broadcasting of the advertisement is limited, and therefore such mobile nodes use solicitation to discover foreign agents. Upon receiving a solicitation message, any intermediate node that has a route to the foreign agent would reply with the advertisement to the initiator of the solicitation. The system also uses ring search method to reduce flooding the network with solicitation where the solicitation initially sent with TTL is equal to one and increased up to seven, and after that, solicitation is flooded throughout the network. However, the system does not specify the process of handoff. The ring search method can also lead to a long delay until a mobile node can discover a route to a foreign agent. _Internet connectivity for ad hoc mobile networks_[56] incorporates Mobile IP with AODV to provide internet connectivity and mobility management for MANET. Mobile nodes and foreign agents are configured to maintain a foreign agent list and mobile node registration lists, respectively. For agent advertisement, foreign agents in the proposed system broadcast advertisement messages periodically, which is additionally used to propagate routing information to allow mobile nodes to get the route to foreign agents. MANET nodes that desire a connection to the internet should process the advertisement message and re-broadcast it. On the other hand, the proposed system supports the mobile node discovery of foreign agents.