An Efficient Multicast Routing Protocol in MANETs

To maintain transmission paths efficiently in a MANET, we use an advanced label mechanism in our new tree-based multicast routing protocol to maintain the topology and multicast groups, and meanwhile use the built backup paths to secure better transmission stability. Simulation results show that, with slightly more control overhead, the new routing protocol can yield constantly higher delivery ratios under increased data flow in comparison to other multicast routing protocols. Keyword: Mobile ad-hoc networks (MANETs), multicast routing protocols, tree-based, label-based, performance evaluation. 1 The Proposed Routing Protocol Multicast routing in MANETs can be mesh or tree based. Mesh-based routing can enhance path stability and repair invalid paths but needs considerable control packets. Tree-based routing which takes less control packets (but is less tolerant for invalid paths) may turn out a better routing choice for super busy MANETs if we can build and maintain paths at less cost than repairing paths. In existing multicast routing protocols [1-5], mesh-based ODMRP [1] lets sources broadcast control packets periodically to maintain groups: The needed control packets will grow when receivers grow, affecting the bandwidth of data transmission while lowering delivery ratios. Tree-based POEM [5] uses labels to mark nodes (assigning each node a unique label) when building the topology and will drop packets if nodes change locations or paths turn invalid. We introduce a new tree-based multicast routing protocol using a more advanced label mechanism to maintain the topology and groups, and to build backup paths which can secure higher stability than other tree-based protocols. To raise the performance at reasonable cost, we meanwhile manage to reduce the required control packets. The flow of our protocol is given below. A. The Operating Process 1. Building the topology: The core node broadcasts the label packet to the network to label each receiver node. Nodes periodically broadcast control packets to neighbor Advanced Science and Technology Letters Vol.41 (Sensor 2013), pp.21-25 http://dx.doi. org/10.14257/astl.2013. 41.06 ISSN: 2287-1233 ASTL Copyright © 2013 SERSC nodes to update neighbor tables and build the topology. (1) Each node receives the label packet and checks its time stamp. (2) Each node gets a label (according to the node level in the tree). (3) Each node updates neighbor information in its neighbor table. (4) After receiving the first label, each node also records the alternative label (according to the alternative level in the tree) for backup use. (5) Use the neighbor information to build the initial topology. 2. Data transmission: When a source receives a request packet, it will (1) check the time stamp in the packet, (2) build a path according to the specified destination labels, (3) check if there is a better routing path built from the backup labels (by checking the similarity – possible parent-child relationship – between destination labels), and (4) transmit the packet by the original path or the better path. 3. Route maintenance (1) Node joining: To join a multicast group, a new node needs to send a request packet to the neighbor nodes and update the information in its neighbor table. (2) Route maintenance: When a path breaks, a node will check neighbors for an alternative path and sends a control packet to update the information in neighbors.