Routing Protocols

•Finding a path from a source to a destination
•Issues
–Frequent route changes
•amount of data transferred between route changes may be much smaller than traditional networks
–Route changes may be related to host movement
–Low bandwidth links
•Goal of routing protocols
–decrease routing-related overhead
–find short routes
–find “stable” routes (despite mobility)

Routing Protocols
•Proactive protocols
–Traditional distributed shortest-path protocols
–Maintain routes between every host pair at all times
–Based on periodic updates; High routing overhead
–Example: DSDV (destination sequenced distance vector)
•Reactive protocols
–Determine route if and when needed
–Source initiates route discovery
–Example: DSR (dynamic source routing)
•Hybrid protocols
–Adaptive; Combination of proactive and reactive
–Example : ZRP (zone routing protocol)


Protocol Trade-offs

•Proactive protocols
–Always maintain routes
–Little or no delay for route determination
–Consume bandwidth to keep routes up-to-date
–Maintain routes which may never be used
•Reactive protocols
–Lower overhead since routes are determined on demand
–Significant delay in route determination
–Employ flooding (global search)
–Control traffic may be bursty

•Which approach achieves a better trade-off depends on the traffic and mobility patterns