Q18Mobile Computing

<h3>Mobile Ad hoc Network (MANET)</h3><p>A Mobile Ad hoc Network (MANET) is a continuously self-configuring, infrastructure-less network of mobile devices connected wirelessly. Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Each must forward traffic unrelated to its own use, and therefore be a router.</p>

<h3>DSDV Routing Protocol</h3><p>Destination-Sequenced Distance-Vector (DSDV) is a table-driven (proactive) routing protocol for ad hoc networks based on the Bellman-Ford algorithm.</p><ul><li><strong>Routing Table:</strong> Every node maintains a routing table that lists all available destinations, the number of hops to reach them, and a sequence number assigned by the destination node.</li><li><strong>Sequence Numbers:</strong> The sequence number is crucial as it distinguishes stale routes from new ones, thereby avoiding routing loops, a common problem in standard distance-vector protocols.</li><li><strong>Updates:</strong> Routing information is updated periodically or when significant topology changes are detected. Nodes transmit their routing tables to their immediate neighbors.</li><li><strong>Update Types:</strong> There are two types of updates: 'Full Dump' (sending the entire routing table, used infrequently) and 'Incremental Update' (sending only the entries that have changed since the last update, used to save bandwidth).</li></ul>

<h3>Working Mechanism</h3><p>When a node receives a routing update, it compares the received sequence number with the one it already has for that destination. The route with the higher sequence number is always preferred. If sequence numbers are identical, the route with the better metric (fewer hops) is chosen. If a link breaks, the node sets the hop count for the broken link to infinity and assigns a new sequence number to indicate the broken route to others.</p>