2.2 Reactive Protocols
In reactive (on demand) protocols, a path discovery mechanism is initiated
only when a source node tries to find a route to a destination node that is
moving around. The path information is maintained as long as it is needed
by the source. Generally, reactive protocols consume fewer overheads than
proactive protocols. When there is no significant movement, there is neither
239 Chapter 10 Location Service, Info. Dissemination and Object Tracking
Dan-Dan Liu and Xiao-Hua Jia
a need to periodically send advertisements, nor to receive them. However, the
delay caused by searching a new route is inevitable.
The Location Aided Routing proposal [14], for example, proposes the use of
position information to enhance the route discovery phase of reactive routing
approaches. A source broadcasts a route request message to all its neighbors,
searching for the destination. Neighbors that are within the request zone will
forward them further. After the destination node, which should be within the
zone, receives such a query, it will send back a route reply message as well as
its current location. Such protocol works as the read-some/write-one scheme.
Nodes don??™t need to update their location to others immediately after the
movements. They reply only when requests are received.
2.3 Rendezvous-Based Protocols
Recently, many protocols have been proposed in a novel fashion, called rendezvous
based protocols.
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