The term MANET (Mobile Adhoc Network)refers to a multihop packet based wireless network composed of a set of mobile nodes that can communicate and move at the same time , without using any kind of fixed wired infrastructure. MNET are actually self organizing and adaptive networks that can be formed and deformed on-the-fly without the need of any centralized administration.
As for other packet data networks, one –to-one communication in a MANET is achieved by unicast routing each single packet. Routing in MANET is challenging due to the constraints existing on the transmission bandwidth battery power and CPU time and the requirement to cope with the frequent topological changes resulting from the mobility of the nodes. Nodes of a MANET cooperate in the task of routing packets to destination nodes since each node of the network is able to communicate only with those nodes located within its transmission radius R, while the source and destination nodes can be located at a distance much higher than R.
A first attempt to cope with the mobility is to use the specific techniques aimed to tailoring the conventional routing protocols to the mobile environment while preserving their nature. For this reason the protocol designed around such techniques are referred to as table-driven or proactive protocols. To guarantee that routing tables are up to date and reflect the actual network topology, nodes running a protocol continuously exchange route updates and re calculate paths to all possible destinations. The main advantage of the proactive protocols is that a route is immediately available when is needed for data transmissions.
A different approach in the design of the routing protocol is to calculate a path only when it is necessary for data transmission. These types of protocols are called as the reactive protocols or on-demand routing protocols. A reactive protocol is characterized by a path discovery procedure and a maintenance procedure. Path discovery is based on a query –reply cycle that adopts flooding of queries. The destination is eventually reached by the query an at least one reply is generated. Path discovery procedure is called when there is a need for data transmission and the source does not the path to the destination. Discovered paths are maintained by the route maintance procedure until they are no longer in used.
As for other packet data networks, one –to-one communication in a MANET is achieved by unicast routing each single packet. Routing in MANET is challenging due to the constraints existing on the transmission bandwidth battery power and CPU time and the requirement to cope with the frequent topological changes resulting from the mobility of the nodes. Nodes of a MANET cooperate in the task of routing packets to destination nodes since each node of the network is able to communicate only with those nodes located within its transmission radius R, while the source and destination nodes can be located at a distance much higher than R.
A first attempt to cope with the mobility is to use the specific techniques aimed to tailoring the conventional routing protocols to the mobile environment while preserving their nature. For this reason the protocol designed around such techniques are referred to as table-driven or proactive protocols. To guarantee that routing tables are up to date and reflect the actual network topology, nodes running a protocol continuously exchange route updates and re calculate paths to all possible destinations. The main advantage of the proactive protocols is that a route is immediately available when is needed for data transmissions.
A different approach in the design of the routing protocol is to calculate a path only when it is necessary for data transmission. These types of protocols are called as the reactive protocols or on-demand routing protocols. A reactive protocol is characterized by a path discovery procedure and a maintenance procedure. Path discovery is based on a query –reply cycle that adopts flooding of queries. The destination is eventually reached by the query an at least one reply is generated. Path discovery procedure is called when there is a need for data transmission and the source does not the path to the destination. Discovered paths are maintained by the route maintance procedure until they are no longer in used.
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