DSDV

DSDV, or Destination-Sequenced Distance-Vector routing, is a proactive routing protocol designed for mobile ad hoc networks (MANETs). It maintains routes to all destinations by periodically exchanging routing tables among nodes, allowing immediate forwarding decisions without a separate route discovery process.

A key feature of DSDV is the use of destination sequence numbers to ensure loop-free and current routes. Each destination has a sequence number that indicates its freshness; higher numbers reflect more recent information. A route is preferred based on the highest destination sequence number, with hop count serving as a secondary criterion when sequence numbers are equal.

Operation: Each node keeps a routing table with entries for every reachable destination, including the next hop, hop count, and the destination's sequence number. The node broadcasts its entire routing table at regular intervals. When topology changes occur, nodes advertise updates, which can be full dumps or incremental updates in some implementations. These updates propagate through the network to maintain consistent routing information.

Advantages and limitations: As a proactive protocol, DSDV reduces route discovery delay and is suitable for networks with relatively stable topology. However, it incurs significant control overhead due to periodic updates, and performance can degrade in highly dynamic or large networks if update traffic becomes heavy. Sequence numbers mitigate routing loops but do not eliminate the burden of maintaining up-to-date tables.

History and context: DSDV was introduced by C. E. Perkins and P. Bhagwat in 1994 as an early MANET routing protocol. It laid foundational concepts for table-driven approaches, influencing subsequent protocols, though modern designs often prioritize scalability and reduced overhead.