Dynamic Source Routing
Dynamic Source Routing or DSR is a routing protocol for wireless mesh networks, an internet over digital radio. It is similar to AODV in that it forms a route when a transmitting computer requests one. However, it has many optimizations to save space, time and reduce the amount of data transmitted on the radios.
One notable optimization is that DSR does not require forwarding computers to have routing tables. Instead, it puts a list of network addresses in each packet. This sounds inconvenient, but there are therefore no routing tables in forwarding computers to be kept up to date, which substantially reduces network traffic. The lack of routing information also means that forwarding computers can be simple and do not require memory.
Another notable optimization is that a DSR computer eavesdrops on the local network traffic to find routing information. This is possible since each packet of normal data traffic has a list of addresses. DSR nodes are also permitted to listen for other nodes' routing requests, routing errors and other information, and exploit those as well.
DSR also has a route-finding protocol similar to AODV's. In lightly populated radio areas, the two protocols therefore have similar behavior. In heavily populated networks, DSR sends about 1/3 as much routing information, mostly because nodes get so much information from eavesdropping, rather than flooding the network with routing requests.
One of the more subtle problems with DSR is that the eavesdropping logic has to force older information out of the internal routing tables, and must be able to ignore aged routing information that is eavesdropped from nodes that are less in touch.
Optimization of DSR nodes' internal routing tables is currently (2005) an area of active research. It may eventually converge on an algorithm much like a Link-state routing protocol, except built from eavesdropped data.
For information on other similar protocols, see the Ad hoc protocol list.
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References
It was first described in:
- David B. Johnson. Routing in Ad Hoc Networks of Mobile Hosts. Proceedings of the Workshop on Mobile Computing Systems and Applications, pp. 158–163, IEEE Computer Society, Santa Cruz, CA, December 1994.
Many successive refinements have been made to DSR, including DSRFLOW.
Categories: Computer network stubs | Wireless networking | Network protocols