Challenges of Routing in Ad-hoc Networks Chandra D Yarlagadda

Ad-hoc Networks No infrastructure No infrastructure Wireless Wireless Node acts as router Node acts as router Used in meetings, emergency situations Used in meetings, emergency situations No home agent or foreign agent No home agent or foreign agent

Conventional Routing Solutions Distance vector routing Distance vector routing 1. Distance in hops 2. Periodic broadcasts 3. Router sends to next hop 4. Fast convergence but bandwidth wasted 5. RIP Link State Link State 1. State of link 2. Topology of entire network 3. Periodic updates 4. Shortest path based on metric 5. More accurate but much more bandwidth wasted 6. OSPF

Problems of Using Conventional Routing protocols Uplink and Downlink Uplink and Downlink Link Redundancy Link Redundancy Routing updates Routing updates Nature of routers Nature of routers

New Approach Route Discovery Route Discovery 1. Simple Method is ARP 2. Flooding 3. Transmissions are broadcast 4. Id’s for duplicate packets 5. Caching of routes for future use

New Approach Route Maintenance Route Maintenance 1. Use of Caching prevents nodes to know change of state 2. Deals with accuracy of the route 3. Hop by Hop acknowledgement 4. Bit in the packet to request acknowledgement

Types of Ad-Hoc routing protocols Table Driven Table Driven Source Initiated Source Initiated

Table Driven Maintain up-to-date information from one node to all other nodes Maintain up-to-date information from one node to all other nodes Information stored in tables Information stored in tables Updates are used to maintain the tables Updates are used to maintain the tables Differ from conventional routing protocols on the basis of tables maintained and updates sent Differ from conventional routing protocols on the basis of tables maintained and updates sent

Destination-Sequenced Distance-Vector Routing (DSDV) Every node contains a table containing all other nodes and the hops required Every node contains a table containing all other nodes and the hops required Sequence numbers to maintain new routes Sequence numbers to maintain new routes Periodic updates are required Periodic updates are required Network traffic is decreased by Network traffic is decreased by Full Dump & Incremental packets Loop Free network Loop Free network Settling Time Settling Time

Wireless Routing Protocol Distance Table Distance Table Routing Table Routing Table Link-Cost Table Link-Cost Table Message Re- transmission List Table Message Re- transmission List Table

Source-Initiated On-Demand Routing Source starts a discovery process Source starts a discovery process Path found only when required Path found only when required Multiple paths are found Multiple paths are found Paths maintained till node is active or is accessible Paths maintained till node is active or is accessible

Ad Hoc On-Demand Distance Vector Routing

Dynamic Source Routing

Comparisions ParametersOn-demandTable-driven Availability of routing informationAvailable when neededAlways available regardless of need Periodic route updatesNot requiredRequired Coping with mobilityLocalized route discoveryInform other nodes to achieve a consistent routing table Traffic generatedGrows with increasing mobility of active routes Greater than that of on-demand routing QoSFew can support QoS, although most support shortest path Mainly shortest path as the QoS metric

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