Abstract
A Mobile Ad-Hoc Network (MANET) is a decentralized network of autonomous mobile nodes able to communicate with each other over wireless links. Due to the mobility of the nodes, the topology of the network may rapidly be changing, making it impossible to use conventional routing tables maintained at fixed points (routers). Instead, each node is required to determine the best route to a given destination node by itself. Given their dynamic nature, route discovery in a MANET differs significantly from the more or less static routes in wired networks: Not all nodes in a MANET necessarily have the same capabilities. Two nodes, even if they are direct neighbors, may differ with respect to signal strength, available power, reliability etc. These differences require much more complicated and particularly more active distributed algorithms in order to maintain an accurate picture of the networks topology, while at the same time providing scalability for potentially large (and ever-growing) networks. At the same time, route discovery must not use up the majority of the often limited bandwidth available to todayâ„¢s mobile devices. If a node A can send packets to a node B, I know that node B can send packets back to node A, and a reverse path can be entered. This is not necessarily the case in a wireless network, where the physical location and the individual poIr resources have great influence upon a nodes transmission capacity and signal strength.MANET routing protocols are IP based and may use unicast, multicast or hybrid approaches and should allow for interaction with standard wired IP services rather than being regarded as a completely separate entity. Both a purely proactive or purely reactive approach to implement a routing protocol for a MANET have their disadvantages. The Zone Routing Protocol, or ZRP, as described in this document combines the advantages of both into a hybrid scheme, taking advantage of pro-active discovery within a nodes local neighborhood, and using a reactive protocol for communication betIen these neighborhoods. The separation of a nodes local neighborhood from the global topology of the entire network allows for applying different approaches and thus taking advantage of each techniques features for a given situation. These local neighborhoods are called zones (hence the name); each node may be within multiple overlapping zones, and each zone may be of a different size. The Negative-acknowledgment (NACK) Oriented Reliable Multicast (NORM) protocol is designed to provide end-to-end reliable transport of bulk data objects or streams over generic IP multicast routing and forwarding services. NORM uses a selective, negative acknowledgment mechanism for transport reliability and offers additional protocol mechanisms to allow for operation with minimal a priori coordination among senders and receivers. A congestion control scheme is specified to allow the NORM protocol fairly share available network bandwidth with other transport protocols such as Transmission Control Protocol (TCP). It is capable of operating with both reciprocal multicast routing among senders and receivers and with asymmetric connectivity (possibly a unicast return path) betIen the senders and receivers. The protocol offers a number of features to allow different types of applications or possibly other higher level transport protocols to utilize its service in different ways.
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