A Survey of Routing Techniques for Mobile Collaborative Virtual Environment Applications <s> Reactive Routing Scheme <s> We argue that there exists a synergy between peer-to-peer (p2p) overlay networks for the Internet and mobile ad hoc networks (MANETs) connecting mobile nodes communicating with each other via multi-hop wireless links-both share the key characteristics of self-organization and decentralization, and both need to solve the same fundamental problem, that is, how to provide connectivity in a decentralized, dynamic environment. We propose Dynamic P2P Source Routing (DPSR), a new routing protocol for MANETs that exploits the synergy between p2p and MANETs for increased scalability. By integrating Dynamic Source Routing (DSR) and a proximity-aware structured p2p overlay routing protocol, DPSR limits the number of the source routes that each node has to discover and rediscover to O(logN), while retaining all the attributes of DSR for dealing with the specifics of ad hoc networks. This is in contrast to the maximum of N source routes each node has to maintain in DSR. Thus DPSR has the potential to be more scalable than previous routing protocols for MANETs, such as DSR and AODV. ::: ::: In addition to being a network layer multi-hop routing protocol, DPSR simultaneously implements a distributed hash table (DHT) in MANETs; it implements the same functionalities as CAN, Chord, Pastry, and Tapestry, which can be exposed to the applications built on top of it via a set of common p2p APIs. <s> BIB001 </s> A Survey of Routing Techniques for Mobile Collaborative Virtual Environment Applications <s> Reactive Routing Scheme <s> The utilization of peer-to-peer (P2P) overlay networks on mobile ad hoc networks (MANET) introduces new services and possibilities such as content based routing and location based services (LBS). A simple layering of both networks is inefficient and does not scale well because the virtual P2P overlay network does not match the frequently changing physical network topology of the MANET. The mobile peer-to-peer (MPP) protocol stack offers a very promising concept by introducing a cross-layer communication channel between the physical network layer and the virtual P2P network layer. This reduces significantly the messaging overhead and increases the search success rate, as we can prove in this work. Therefore, we describe an implementation of the MPP protocol stack in the Network Simulator 2 (ns-2). With this implementation, we prove the significant performance improvements which can be achieved with MPP, to allow P2P networking in mobile ad hoc environments. <s> BIB002 </s> A Survey of Routing Techniques for Mobile Collaborative Virtual Environment Applications <s> Reactive Routing Scheme <s> P2P systems for mobile ad hoc networks are currently an open research area. Most of the existent solutions were thought for the wired networks, where thousands of nodes participate to the same service, while ad hoc networks are generally characterized by limited dimensions and scarce resources. In this paper, a performance evaluation of a structured P2P system (Pastry), running on a real ad hoc network, will be presented, and a new optimized solution, called CrossROAD, will be defined. CrossROAD exploits a cross-layer architecture to reduce the communication overhead introduced by Pastry and, at the same time, maintains all the basic principles of structured overlay networks. <s> BIB003 </s> A Survey of Routing Techniques for Mobile Collaborative Virtual Environment Applications <s> Reactive Routing Scheme <s> This paper presents a reliable communication method for assuring stable peer-to-peer (P2P) data sharing in mobile ad hoc networks. The method for guaranteeing reliable P2P data sharing mainly tackles the problem of disconnection due to the sudden disappearance of one or more nodes involved in the active transmission route. We propose a communication mechanism which includes two schemes; a configuration scheme and a routing scheme. The configuration scheme discovers mobile devices and automatically constructs a MANET (mobile ad hoc network) using a dynamic IP addressing technique. The routing scheme allows for reliable transmission of data via mobile devices. It does this using our reconnection mechanism that finds emergency routes in instances of abrupt disconnection. We developed a reliable mobile P2P data sharing system with these two schemes. We also performed some experiments for verifying our communication method for stable transmission using our real testbed. The experiments lead us to conclude that our communication method is effective and assures reliable P2P data sharing over mobile ad hoc networks. Our reconnection mechanism affords a good ratio of successful transfers for services requested by users. In addition, our system minimizes the number of relayed transmissions using our scanning table and lookup table. This provides a good transmission performance and reliability, but our system takes a relatively long time for discovery. <s> BIB004
We describe in this section some approaches that uses reactive routing scheme. In BIB003 authors studies the performance of Pastry like algorithm over MANETs using hop-by-hop routing AODV  . Simulation results has shown a poor network performances due to heavy network overhead need it to maintain large numbers of connections between nodes. An alternative solution may be proposed to overcome this weakness by introducing a cross layer approach. Hu et al BIB001 propose an evaluation of a scalable solution over MANETs. The idea is based on a combination of the DSR  and Pastry  to create Dynamic per-to-peer source routing called DPSR. An ID is assigned to each node using a specific hash. Messages are routed based on the hash address destination. This strategy enable fast look up resolution in spite of highly dynamic nodes. Pusha et al  provide an efficient way to construct a mobile file sharing application using Pastry  and DSR  in an integrated approach. With this integration, the routing structure in DHT is integrated with the routing cache of DSR into one structure to optimize the routing performance and to learn about paths to close nodes. Experimental simulations have delivered promising results, which demonstrate the feasibility of this approach. In this section we describe some approaches that uses proactive ad-hoc routing protocols. ORION system BIB004 explores the concept of cross-layer over MANET as a scheme combining the discovery process routing at the network layer and the query process at the application layer. The basic of ORION is based on the AODV routing protocol. Performance results has shown unnecessary network overhead due to application layer routing. MPP BIB002 (Mobile Peer-to-peer Protocol) is another example of cross layer approach, and is based on DSR  ad-hoc routing protocol. This protocol establishes a communication channel between application layer and network layer to deploy peer-to-peer system effectively in mobile environment. Each node announces itself to the routing protocol, and a search request is broadcasted to all nodes. MPP relies on flooding for query lookup. It is clear to see that MPP does not scale when the network size and the network query rates increases.