notes-shivam

4. MANET

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5. MANET (Mobile Ad-hoc Networks)

  1. A Mobile Ad-hoc Network (MANET) is a self-configuring, infrastructure-less network of mobile devices connected wirelessly.
  2. Each node in a MANET acts both as a host and as a router to forward packets to other nodes.
  3. The network topology changes dynamically due to node mobility, requiring adaptive and distributed routing protocols.
  4. Communication occurs either directly between nodes or via intermediate nodes in a multi-hop fashion.
  5. MANETs are typically used in scenarios where setting up a fixed infrastructure is difficult or impossible, such as disaster recovery, military operations, or temporary events.
  6. Challenges in MANETs include
    1. dynamic topology management
    2. limited bandwidth
    3. constrained energy resources
    4. routing overhead
    5. security vulnerabilities.
  7. Protocols used in MANETs are generally categorized into proactive, reactive, and hybrid types based on route discovery strategy.

5.2 Destination Sequenced Distance Vector (DSDV) Protocol

  1. DSDV is a proactive (table-driven) routing protocol based on the classical Bellman-Ford algorithm, adapted for ad-hoc networks.

  2. Each node maintains a routing table that contains the next hop, metric (usually hop count), and a sequence number for each reachable destination.

  3. Sequence numbers, generated by the destination node, help distinguish stale routes from fresh ones and prevent routing loops.

  4. Routing updates are periodically broadcasted across the network and also triggered by significant topology changes.

  5. There are two types of updates: full dump (entire table) and incremental update (only changed entries).

  6. DSDV ensures that routes are immediately available when needed, thus offering low-latency communication.

  7. However, it suffers from high routing overhead due to frequent table updates, making it inefficient in highly dynamic environments.

5.3 Ad-hoc On-Demand Distance Vector (AODV) Protocol

  1. AODV is a reactive routing protocol that establishes routes only when required by source nodes.

  2. When a source node wants to communicate, it broadcasts a Route Request (RREQ) packet throughout the network.

  3. Nodes receiving the RREQ either reply with a Route Reply (RREP) if they have a route or forward the request until it reaches the destination.

  4. Once the RREP is received, the route is established and used for data transmission.

  5. Sequence numbers ensure the most recent route is chosen and help in maintaining loop-free routes.

  6. Routes are maintained as long as they are needed and are discarded if they become inactive or broken.

  7. Route Error (RERR) messages are used to inform nodes about link failures so they can invalidate routes.

  8. AODV reduces routing overhead compared to proactive protocols and is more scalable in dynamic networks, but it may incur initial delay due to route discovery.

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