Introduction to Wireless Ad-Hoc Networks Routing

Michalis FaloutsosSome slides borrowed From Guor-Huar Lu

Outline

ChallengesDesign Goals Specified by MANET (for now…)Types of RoutingProtocols in DetailConclusion

Challenges

Dynamic TopologiesBandwidth-constrained, variable capacity linksEnergy-constrainedLimited Physical securityScalability

Types of routingFlat Proactive Routing• Link state Fish-Eye Routing, GSR, OLSR.• Table driven: Destination-Sequenced Distance Vector (DSDV), WRP)

On-Demand or Reactive Routing• Ad hoc On-demand Distant Vector (AODV)• Dynamic Source Routing (DSR)

Hybrid Schemes• Zone Routing ZRP, SHARP (proactive near, reactive long distance)• Safari (reactive near, proactive long distance)

Geographical RoutingHierarchical: One or many levels of hierarchyRouting with dynamic address• Dynamic Address RouTing (DART)

Proactive Protocols

Proactive: maintain routing information independently of need for communicationUpdate messages send throughout the network periodically or when network topology changes.Low latency, suitable for real-time trafficBandwidth might get wasted due to periodic updatesThey maintain O(N) state per node, N = #nodes

On-Demand or Reactive Routing

Reactive: discover route only when you need itSaves energy and bandwidth during inactivityCan be bursty -> congestion during high activitySignificant delay might occur as a result of route discoveryGood for light loads, collapse in large loads

Hybrid Routing

Proactive for neighborhood, Reactive for far away (Zone Routing Protocol, Haas group)Proactive for long distance, Reactive for neighborhood (Safari)Attempts to strike balance between the two

Hierarchical Routing

Nodes are organized in clustersCluster head “controls” clusterTrade off• Overhead and confusion for leader election• Scalability: intra-cluster vs intercluster

One or Multiple levels of hierarchy

Geographical Routing

Nodes know their geo coordinates (GPS)Route to move packet closer to end pointProtocols DREAM, GPSR, LARPropagate geo info by flooding (decrease frequency for long distances)

Theoretical perspective

The capacity of a wireless network is

Where N nodes, and C channel capacity

Explanation: N nodes in the fieldDestinations are random On average N^0.5 hops per pathEach node has N^0.5 paths go throughGupta Kumar paper

Mobility increases capacity

Grossglausser and Tse (infocom 2001)Statement: if nodes move they will enentually carry the info where you wantProtocol: • sender send one copy to receiver or one neighbor• Sender and relay will at some run into destination and

send the packetAll paths are at most two hopsThey show that the capacity of the network does not go to zeroTradeoff?

Hierarchical routing: bounds

Cluster nodes, and route between and within clustersLocation management: finding whereRouting finding how to get thereMultiple levels: log(N) levelsLocation Mgm: Each nodes stores O(N) locationsRouting overhead: O(log^3N)Dominating factor: location management and not the routingLocation mgmt handoff: O(log^2N)See Susec Marsic, infocom 02

Types of routingFlat Proactive Routing• Link state Fish-Eye Routing, GSR, OLSR.• Table driven: Destination-Sequenced Distance Vector (DSDV), WRP)

On-Demand or Reactive Routing• Ad hoc On-demand Distant Vector (AODV)• Dynamic Source Routing (DSR)

Hybrid Schemes• Zone Routing ZRP, SHARP (proactive near, reactive long distance)• Safari (reactive near, proactive long distance)

Geographical RoutingHierarchical: One or many levels of hierarchyRouting with dynamic address• Dynamic Address RouTing (DART)

Proactive: DSDV - Destination-Sequenced Distance Vector Algorithm

By Perkins and Bhagvat Based on Bellman Ford algorithm• Exchange of routing tables• Routing table: the way to the destination, cost

Every node knows “where” everybody else is• Thus routing table O(N)

Each node advertises its position• Sequence number to avoid loops• Maintain fresh routes

DSDV details

Routes are broadcasted from the “receiver”• Nodes announce their presence: advertisements

Each broadcast has• Destination address: originator• No of hops• Sequence number of broadcast

The route with the most recent sequence is used

Reactive: Ad-Hoc On-demand Distance Vector Routing (AODV)

By Perkins and RoyerSender tries to find destination:• broadcasts a Route Request Packet (RREQ).

Nodes maintain route cache and use destination sequence number for each route entryState is installed at nodes per destinationDoes nothing when connection between end points is still validWhen route fails• Local recovery• Sender repeats a Route Discovery

Route Discovery in AODV 1

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SourceDestination

Propagation of Route Request (RREQ) packet

Route Discovery in AODV 2

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SourceDestination

Path taken by Route Reply (RREP) packet

In case of broken links…

Node monitors the link status of next hop in active routesRoute Error packets (RERR) is used to notify other nodes if link is brokenNodes remove corresponding route entry after hearing RERR

Dynamic Source Routing (DSR)

Two mechanisms: Route Maintenance and Route DiscoveryRoute Discovery mechanism is similar to the one in AODV but with source routing insteadNodes maintain route cachesEntries in route caches are updated as nodes learn new routes.Packet send carries complete, ordered list of nodes through which packet will pass

When Sending Packets

Sender checks its route cache, if route exists, sender constructs a source route in the packet’s headerIf route expires or does not exist, sender initiates the Route Discovery Mechanism

Route Discovery 1 (DSR)

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<1><1,2>

<1,3,5>

<1,3,5,7>

<1,4,6>

<1,4>

<1>

<1><1,3>

SourceDestination

Building Record Route during Route Discovery

Route Discovery 2 (DSR)

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<1,4,6>

<1,4,6>

<1,4,6>

Source Destination

Propagation of Route Reply with the Route Record

Route Maintenance

Two types of packets used: Route Error Packet and AcknowledgementIf transmission error is detected at data link layer, Route Error Packet is generated and send to the original sender of the packet.The node removes the hop is error from its route cache when a Route Error packet is receivedACKs are used to verify the correction of the route links.

The Zone Routing Protocol (ZRP)

Hybrid SchemeProactively maintains routes within a local region (routing zone)Also a globally reactive route query/reply mechanism availableConsists of 3 separate protocolsProtocols patented by Cornell University!

Intrazone Routing Protocol

Intrazone Routing Protocol (IARP) used to proactively maintain routes in the zone.Each node maintains its own routing zoneNeighbors are discovered by either MAC protocols or Neighbor Discovery Protocol (NDP)When global search is needed, route queries are guided by IARP via bordercasting

Interzone Routing Protocol

Adapts existing reactive routing protocolsRoute Query packet uniquely identified by source’s address and request number.Query relayed to a subset of neighbors by the bordercast algorithm

Comparisons 1

Things in common:• IP based operation• Distributed operation• Loop-free routing• Very little or no support for sleep period

operation and security

Comparisons 2

FSR AODV DSR ZPR

Source Routing

No No Yes No

Periodic message

Yes No No Yes (Locally)

Functioning Proactively

Yes No No Yes (Locally)

Functioning Reactively

No Yes Yes Yes (Globally)

DSDV

Conclusion

On-demand routing protocols (AODV and DSR) are gaining momentum.More analysis and features are needed (Performance comparison between protocols, QoS extension and analysis, multicast, security issues etc…)Good paper (though old):

A review of current routing protocols for ad-hoc mobile wireless networks, E. Royer, C.K. Toh

Performance?

End-to-end data throughput and delayRoute acquisition timePercentage of out-of-order deliveryEfficiency:• Average number of data bits transmitted/data bits

delivered• Average number of control bits transmitted/data bits

delivered• Average number of control and data packets

transmitted/data packet delivered

Parameters

Network SizeConnectivity (average degree of a node)Topology rate of changeLink capacity (bps)Fraction of unidirectional linksTraffic patternsMobilityFraction/frequency of sleeping nodes

References

Mobile Ad hoc Networking (MANET): Routing Protocol Performance Issues and Evalution Considerations (RFC 2501)P. Misra., “Routing Protocols for Ad Hoc Mobile Wireless Networks”, http://www.cis.ohio-state.edu/~jain/cis788-99/adhoc_routing/The Zone Routing Protocol (ZRP) for Ad Hoc Networks <draft-ietf-manet-zone-zrp-04.txt>Fisheye State Routing Protocol (FSR) for Ad Hoc Networks <draft-ietf-manet-fsr-03.txt>Ad hoc On-demand Distance Vector (AODV) Routing <draft-ietf-manet-aodv-11.txt>The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks (DSR) <draft-ietf-manet-dsr-07.txt>

Fisheye State Routing (FSR)

Node stores the Link State for every destination in the networkNode periodically broadcast update messages to its neighborsUpdates correspond to closer nodes propagate more frequently

Multi-Level Scope (FSR)

• Central node (red dot) has the most accurate information about nodes in white area and so on.•Parameters: Scope level/radius size

ZPR architecture

NDP IARP IERP ICMP

BRP

ZRP

IP

A B Information passed from protocol A to B

A B Exchange of packets between protocol A and B

Design Goals

Peer-to-peer mobile routing capability in mobile, wireless domain.Intra-domain unicast routing protocol:• Effective operation over a wide range of mobile

networking scenarios and environments• Supports traditional, connectionless IP services• Efficiently manages topologies changes and traffic

demands

Desired properties

Distributed operationLoop freedomDemand-based operationProactive operationSecurity“Sleep” period operationUnidirectional link support