Geo-assisted Multicast Inter-Domain Routing (GMIDR) Protocol for MANETs Konglin Zhu * , Biao Zhou + , Xiaoming Fu * , Mario Gerla + ∗ Institute of Computer Science, University of Goettingen, Germany + Department of Computer Science, University of California, Los Angeles, USA Email: {zhu, fu}@cs.uni-goettingen.de {zhb, gerla}@cs.ucla.edu Abstract— Large military ad hoc networks are often charac- terized by the interconnection of heterogeneous domains. The same trend is emerging in civilian MANETs (e.g., search and rescue, vehicular networks). In these networks it is important to be able to efficiently propagate information across domains in multicast mode (e.g., situation awareness dissemination, com- mands, streams). Several multicast protocols have been developed for single domain MANET. However, few can be extended to inter-domain operation. In fact, multicast routing across different MANET domains faces the challenges of node motion, topology changes, dynamic gateway election and, possibly, connectivity interruption. To overcome these challenges, especially to achieve routing scalability and at the same time maintains efficient rout- ing, this paper proposes the Geo-assisted Multicast Inter-domain Routing (GMIDR) protocol based on geographical assistance and cluster technology. Intensive simulation results show that the GMIDR protocol is scalable and stable with various numbers of multicast group members, and it outperforms other multicast protocols. Geocast by applying GMIDR shows the flexibility of the protocol. I. I NTRODUCTION The mobile ad-hoc network (MANET) inter-domain mul- ticasting comes out as an efficient communication paradigm for the emerging multicast communications across multiple domains, e.g., large military operations, emergency and rescue missions. For instance, a commander-in-general would send the order to the army, navy and air forces to cooperate each other to finish an overall military mission. Also, a remote rescue surgery may need cooperation from multiple doctors physically located in different regions. These above-mentioned missions cover several areas and need fast response. Therefore, it is very important to define a network routing policy to disseminate data to different domains. Some civilian MANET applications would also require an inter-domain multicast routing protocol. For example, a vehicle driver may wish to send a traffic situation message to a group of cars in different domains. Multicast TV [4] on public transportation such as buses requires scalable transmission to provide the multimedia service. Towards this end, Ji and Corson have developed the Dif- ferential Destination Multicast (DDM) protocol [1] which aims to adapt to small multicast groups. SENCAST [2] is a routing protocol designed for large ad hoc emergency network. However, these protocols are hard to meet the inter-domain multicast routing requirements. To the best of our knowledge, very few multicast procotols are designed to inter-domain environment. There is one feasible solution to extend the intra- domain routing protocol to the inter-domain routing protocol is adding inter-domain functions into the intra-domain proto- col. However, the revision may introduce additional control overhead and decrease the packet delivery ratio. To build an efficient and scalable multicast routing, we introduce the geographical assisted multicast inter-domain routing (GMIDR) protocol. The main goal of our protocol is to achieve a scalable and efficient multicast routing in inter-domain networks. Also, it is important to minimize the control overhead and provide ways to handle inter-domain policy compliance and heterogeneity. We utilize geo-routing protocol and cluster techniques to achieve these goals. The proposed GMIDR applies the geo- routing strategy to reduce network overhead. Namely, each node is aware of its own geographical location, and the geo- routing protocol looks for the node in the multicast group based on the location information, which consumes much less control overhead. To enable scalable and efficient routing, cluster techniques is introduced. Clusters as the basic structure in GMIDR in each domain help the protocol to obtain effi- cient communication among different domains. Furthermore, multicast group cluster heads (GCHs) are elected within the multicast group covering the entire multicast group. A multicast tree is established from source to each GCH instead of each member in the multicast group. The GCH acts as the stronghold in its group cluster. It obtains the data from outside the group cluster, and delivers to all its children within the group cluster. By taking advantage of GCH, our proposed protocol consumes very low control overhead on the group management. The remainder of this paper is organized in the following way. The related work is briefly reviewed in section II. The basic structure behind the protocol is discussed in section III. We describe the protocol design of GMIDR in details in section IV. The performance evaluations are presented in section V and the last section of the paper is our conclusion. II. RELATED WORK A. Geo-based inter-domain routing (GIDR) Geo-based inter-domain routing (GIDR) [5] protocol for MANET is an efficient unicast protocol to apply the clustering technique and geo-routing protocol to obtain the efficient com- munication and achieve the scalability. Clusters are assigned 978-1-61284-231-8/11/$26.00 ©2011 IEEE This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE ICC 2011 proceedings