lec1029 - Comparison between DSR and AODV DSR Overview AODV...

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Comparison between DSR and AODV DSR Overview AODV Overview Similarity Difference Consequence
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DSR Overview Source routing: routes are stored in a route cache, data packets carry the source route in the packet header Route discovery Condition: a node sends data to a destination for which it does not know the route Actions: source floods the network with RREQ. Each node receiving RREQ rebroadcasts it unless it is destination or it has the route to the destination in its cache. Route reply A destination node or a node knowing the route to the destination in its cache replies with RREP. RREQ and RREP are also source routed. Route carried back by RREP is cached at the source
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DSR Overview (II) Error handling: If any link on a source route is broken, the source is notified by a RERR packet Source removes any route using this link from its cache A new “Route Discovery” process must be initiated by the source, if the route is needed. Optimizations: Salvaging: an intermediate node uses an alternative route from its cache, when a data packet meets a failed link on its source route Gratuitous route repair: A source node receiving RERR piggybacks the RERR in the following RREQ, to clean the caches of other nodes that may use the failed link Promiscuous listening: when a node overhears a packet not addressed to itself, it checks whether the packet could be routed via itself to gain a shorter route. If so, sends a gratuitous RREP to the source with the new better route.
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AODV Overview Discovers routes on an “on-demand” basis via a similar route discovery process, but uses a different mechanism to maintain routing info. AODV uses routing table, one entry per destination. It relies on routing table entries to propagate a RREP back to the source, and route data packets to the destination. AODV uses sequence # maintained at each destination to determine freshness of routing info. And to prevent routing loops. These sequence # are carried by all routing packets.
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AODV Overview (II) Maintain timer-based states in each node. A routing table entry is expired if not used recently. A set of predecessor nodes is maintained for each routing table entry, indicating neighbors that use the entry to route packets. These nodes are notified with RERR when the next-hop link breaks. Each predecessor node forwards RERR to its predecessors, erasing all routes using the broken link. Optimization: Expanding ring search: control the RREQ flood in the route discovery process. The search is controlled by the TTL field, increasingly larger neighborhoods are searched to find the destination.
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Both discover routes only in the presence of data packets in the need for a route to the destination Route discovery is based on query and rely cycles and route information is stored in all intermediate nodes on the route Route table entires (AODV), route caches (DSR)
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This note was uploaded on 03/19/2012 for the course CS 1313 taught by Professor Aman during the Spring '12 term at Punjab Engineering College.

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lec1029 - Comparison between DSR and AODV DSR Overview AODV...

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