Mobile Reliable Multicast Protocols In Manet Research

Fixed networks take advantage of their static nature in two ways. First, they proactively distribute network topology information among the nodes, and each node pre-computes routes through that topology using relatively inexpensive algorithms. Second, fixed networks embed routing hints in node addresses because the complete topology of a large network is too unwieldy to process or distribute globally. Neither of these techniques work well for networks with mobile nodes because movement invalidates topology information and permanent node addresses cannot include dynamic location information.Mobile ad hoc networks (MANETs) are self-organizing mobile wireless networks that do not rely on a preexisting infrastructure to communicate. Nodes of such networks have limited transmission range, and packets may need to traverse multiple other nodes before reaching their destination.Providing reliable multicast is a basic requirement to build advanced distributed protocols. One of the specially challenging reliable multicast environments is MANETs.In this thesis, we investigate on three categories of MANETs reliable routing protocols; unicast protocols, multicast protocols and broadcast protocols; on the reliable unicast routing protocols, they can be divided into topology-based protocols and geographical-based protocols. Topology-based protocols can be divided into proactive protocols, reactive protocols and hybrid protocols. Most of the proactive routing protocols are based on shortest path algorithms adapted to the mobile environment. As a result, when the mobility rate of nodes is high, proactive protocols are infeasible since they cannot keep up with the changes in the topology. Thus, several proactive routing protocols were forsaken because of their high communication overhead. In reactive routing algorithms, route discovery to a destination node is only initiated when a data packet needs to be transmitted to that node. Hybrid routing protocols are mixed between those proactive and reactive protocols. The other category of unicast routing protocols is geographical-based protocols, these protocols assume that the source also knows the location of thedestination, and the packets could be efficiently forwarded by intermediate nodes with aid of the location information.Although multicast transmission has not been widely deployed in the current MANET, it will become very important in multimedia communications in the near future. The idea of multicast protocols is based on query-response mechanism similar to that of unicast protocols. The basic operations in multicast routing are similar to those in unicast routing, except for a little modification; in unicast routing operations, every destination has a unique sequence number. Likewise, every multicast group also has a sequence number to indicate the freshness of the multicast routing information. To support multicast transmission, a multicast tree is formed on-demand to include all the group members. There have been many multicast routing protocols proposed for MANETs. They could be divided into two groups: tree-based protocols and mesh-based protocols; the tree-based protocols originate from their counterparts in hardwired networks, the mesh-based protocols use a mesh instead of a share multicast tree for packet delivery, which provides redundant links among group members. Compared with tree-based protocols, they may consume more bandwidth.Reliable broadcast protocols are techniques to achieve multicast communications with high-level communications. They may have advantages over other protocols. Broadcasting is used in the route discovery process in several routing protocols, when advising an error message to erase invalid routes from the routing table, or as an efficient mechanism for reliable multicast in a fast-moving MANET. Broadcast protocols can be classified into deterministic and probabilistic protocols; Deterministic protocols provide delivery guarantees for the delivery of messages to a group of nodes in a MANET. Protocols offering this kind of delivery guarantee most often tend to detect and repair failures, either at the source, or locally where the route is broken. Probabilistic protocols are protocols that guarantee delivery with a certain probability.Although there are many kinds of unicast, multicast and broadcast routing protocols for the MANETs, it seems that one protocol cannot fit all the different scenarios and traffic patterns of MANETs applications. Proactive routing protocols are well suited for small-scale, broadband MANETs with high mobility, while reactive routing protocols are well suited for a large-scale, narrow-band MANETs with low mobility.In this thesis, we have also proposed a Hypercube-based Virtual Dynamic Backbone (VDB) model and some simple algorithms for a multicast routing protocol. The proposed model is derived from n-dimensional hypercube networks, which have many excellent properties, such as high fault tolerance, short diameter, regularity and symmetry. Furthermore, the hypercube in our proposed model is most probably an incomplete hypercube, in which certain parts of its nodes/links are missing due to mobility and failure of nodes. Hypercube-based Virtual Dynamic Backbone model has high availability and good load balancing properties in large-scale MANETs. Multicast can be performed within only the VDB structure. Therefore, it improves the scalability of such a protocol.