The term network topology refers to the wav in which

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Unformatted text preview: he source node must have fairly comprehensive information about the network environment. However, the routing decision process is efficient because the intermediate nodes need not make any routing decision. A drawback of the method is that the path cannot be changed after the packet has left the source node, rendering the method susceptible to component failures. 2. Hop-by-hop routing. In this method, each node along the path decides only the next node for the path. That is, each node maintains information about the status of all its outgoing channels and the adjacent nodes and then selects a suitable adjacent node for the packet and transmits it to that node. The routing decisions are typically based on the channel availability and the readiness of the adjacent nodes to receive and relay the packet. The method requires that each node must maintain a routing table of some sort. However, as compared to the source routing method, this method makes more efficient use of network bandwidth and provides resilience to failures because alternative paths can be used for packet transmissions. 3. Hybrid routing. This method combines the first two methods in the sense that the source node specifies only certain major intermediate nodes of the complete path, and the subpaths between any two of the specified nodes are decided by the method of hop-by-hop routing. Static and Dynamic Routing Depending on when the information used for making routing decisions is specified and how frequently it is modified, routing algorithms are classified into the following two types [Reprinted, with permission, from the book titled Distributed Operating Systems: Concepts and Design by Pradeep K. Sinha. © 1997 IEEE]: 1. Static routing. In this method, routing tables (stored at the nodes) are set once and do not change for very long periods of time. They are changed only when the network undergoes major modifications. Static routing is also known as fixed or deterministic routing. Static routing is simple and easy to implement. However, it makes poor use of...
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