Destination-Sequenced Distance Vector routing
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Destination-Sequenced Distance-Vector Routing (DSDV) is a table-driven routing scheme for ad hoc mobile networks based on the Bellman-Ford algorithm. It was developed by C. Perkins in 1994. The main contribution of the algorithm was to solve the Routing Loop problem. Each entry in the routing table contains a sequence number, the sequence numbers are generally even if a link is present else an odd number is used. The number are generated by the destination, and the emitter needs to send out the next update with this number. Routing information is distributed between nodes by sending full dumps infrequently and smaller incremental updates more frequently.
For example the routing table of Node A in this network is
| Destination | Next Hop | Number of Hops | Sequence Number | Install Time |
|---|---|---|---|---|
| A | A | 1 | A 46 | 001000 |
| B | B | 2 | B 36 | 001200 |
| C | B | 3 | B 28 | 001500 |
Naturally the table contains description of all possible paths reachable by node A, along with the next hop, number of hops and sequence number.
Contents |
[edit] Selection of Route
If transmitter has received some new information, then it uses the latest sequence number. If sequence number is same better metric is used. Stale entries are those entries that have not been updated for last dew time. Such entries as well as the routes using those node as next hop are also deleted.
[edit] Advantages
DSDV was one of the early algorithms available. It is quite suitable for creating ad hoc networks with small number of nodes. Since no formal specification of this algorithm is present there is no commercial implementation of this algorithm. Many improved forms of this algorithm have been suggested.
[edit] Disadvantages
- DSDV requires a regular update of its routing tables, thus reducing the bandwidth efficiency.
- It is not suitable for very large network i.e less scalability.
- Whenever topology of network changes, it makes the network unstable for few period of time. Thus it is not suitable of highly dynamic network.
[edit] References
- Perkins, Charles E. and Bhagwat, Pravin (1994). "Highly Dynamic Destination-Sequenced Distance-Vector Routing (DSDV) for Mobile Computers" (pdf). Retrieved on 2006-10-20.
