reactive routing protocols for ad hoc mobile wireless networks

Reactive Routing Protocols for Reactive Routing Protocols for Ad hoc Mobile Wireless Ad hoc Mobile Wireless NetworksNetworks

OverviewOverviewAd Hoc Routing Protocols

Table-Driven Demand-Driven

DSDV WRPAODV DSRLMR ABR

SSR

ReactiveProactive

CGSR

TORA

Elizabeth Royer and Chai Keong Toh, “A review of Current Routing Protocols for Ah Hoc Mobile Wireless Networks”, IEEE personal Communications April 1999

Proactive vs ReactiveProactive vs ReactiveProactive Reactive

Route from each node to every other node in the network

Routes from Source to Destination only

Routes are ready to use instantaneously

Routes constructed when needed, higher connection setup delay

Periodic route-update packets Route update when necessary

Large routing tables Small or No routing tables

On-Demand Routing Protocols

Source Routing Hop-by-Hop Routing

ABR DSRAODV LARLMR RDMARSSA

TORA


Source Routing vs Hop-by-Hop RoutingSource Routing vs Hop-by-Hop RoutingSource Routing Hop-By-Hop Routing

Data packets carry the complete addresses from source to destination

Data packets carry the address of the destination and the next hop

No routing table in intermediate nodes

All nodes maintain localized routing tables

Not Scalable Scalable

General PropertiesGeneral PropertiesLoop Free RoutingTwo Operation Phases

◦ Route Establishment Route Request RouteRequest Packet, flooded

by the Source node Route Reply RouteReply Packet, returned to

source node by Destination or Intermediate node◦ Route Maintenance

Route Reconstruction Route Deletion

ProtocolsProtocolsDSR: Dynamic Source RoutingABR: Associativity-Based RoutingSSA: Signal Stability-Based Adaptive Routing

AlgorithmAODV: Ad Hoc On-Demand Distance VectorLAR : Location Aided Routing ProtocolRDMAR: Relative Distance Micro-Discovery

Ad Hoc RoutingLMR: Light-weight Mobile RoutingTORA: Temporally Ordered Routing

AlgorithmARA: Ant-colony-based Routing Algorithm




TORA


Dynamic Source Routing Dynamic Source Routing (DSR)(DSR)Full source-route is aggregated in

RouteRequest, and sent back in RouteReply

Each data packet carry the full address for all nodes along the path

Can store Multiple routes to destination

Good for Small/ Low mobility networks

DSR– Route DiscoveryDSR– Route Discovery◦ Source Node broadcast RouteRequest packet◦ Each Intermediate node do the following steps:

If request received before discard If node ID is listed in request discard If Route to the destination is available send

RouteReply to the source node with full path Otherwise append node ID and rebroadcast

◦ When destination is reached return RouteReply with full path

◦ Intermediate nodes cache all paths they overhear◦ Source node caches all paths received and choose

Shortest Path

DSR - Route RequestDSR - Route Request

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RouteRequest Dropped

DSR - Route ReplyDSR - Route Reply

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DSR– Route MaintenanceDSR– Route Maintenance◦ Triggered when a link breaks between two

nodes along the path from the Source to the destination

◦ Node who discover the break send a RouteError to inform the source node about the broken link

◦ Source Node erase the route from the cache, and Use another cached routes, Or Request a new Route

DSR – Route MaintenanceDSR – Route Maintenance

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DSRDSRPromiscuous mode, intermediate

nodes learns about routes breaksDuring network partition, if the

destination is in different partition a backoff algorithm is used to prevent frequent RouteRequest broadcast

DSR -- ConcernsDSR -- ConcernsScalabilityLarge overhead in each data

packetNo Local repair of the broken link Stale cache information could

result to inconsistence during route reconstruction

Poor Performance as Mobility increases

Associativity-Based Routing Associativity-Based Routing (ABR)(ABR)Select Longer-Lived routesBeacon based protocol Defining the Location Stability

between nodes◦ Used as a metric instead of shortest hop◦ Determined by beacon counting

Links between nodes classified into Stable and Unstable link according to beacons counts

ABR– Route DiscoveryABR– Route Discovery◦Source Node broadcast RouteRequest packet

◦Each intermediate node do the following steps: If request received before discard If node ID is listed in request discard If route to the destination is available

send RouteReply Otherwise append node ID and Beacon

Count and rebroadcast

ABR– Route DiscoveryABR– Route Discovery◦Destination node

Once get the first RouteRequest, it waits for certain period to receive multiple RouteRequests

From multiple routes, it selects the route with maximum proportion of stable links

If more than one route has the maximum proportion of stable links, the shortest path is selected

Only single route is selected by the destination

ABR - Route RequestABR - Route Request

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Unstable Link

ABR - Route ReplyABR - Route Reply

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ABR – Route MaintenanceABR – Route MaintenanceTry to bypass the broken link without

flooding the RouteRequest globally Downstream node, sends RouteError to the

destination, deleting cache entries along the path

Upstream node broadcasts a RouteRepair with limited time to live◦ If failed, next upstream node broadcast

RouteRepair◦ Is successful, new route is used

If the process traverse near source node, a new RouteRequest is initiated

ABR – ConcernsABR – ConcernsChosen path may not be shortest

pathMay lead to higher delay in route

repairs Single path selectionHigh cost of periodic beaconing

◦Power ◦Bandwidth

Signal Stability-based adaptive Signal Stability-based adaptive routing algorithm (SSA)routing algorithm (SSA)

Derivative of ABR Adds Signal Strength as a prime

metricIn addition to beacon count, each

node keep record of the signal strength of other neighbors

Links are classified as Strong/Stable links vs Weak/unstable links

SSA– Route DiscoverySSA– Route DiscoveryRouteRequests are forwarded through

strong/stable links onlyRouteRequest received through

weak/unstable links are droppedFailed RouteRequest flood route

discovery without Signal strength metric

Destination node,once get the first RouteRequest over stable links, it sends RouteReply

SSA - Route RequestSSA - Route Request

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Unstable Link

SSA - Route ReplySSA - Route Reply

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SSR – Route MaintenanceSSR – Route MaintenanceEnd nodes of the broken links

notify source and destinationErasing cache entries along the

pathSource broadcast a new

RouteRequest to find Stable link

SSA – ConcernsSSA – ConcernsRestrict condition on forwarding

RouteRequest large setup time in case no stable links are found




TORA


Ad Hoc On-Demand Distance Ad Hoc On-Demand Distance Vector Routing (AODV)Vector Routing (AODV)

Source Routing (DSR, ABR and SSA) is good for smaller networks due to large data packet overhead

AODV:◦ Hop by Hop basis◦ No need to include the full path in the data

packet◦ Update Neighborhood information through

periodic beacons

AODV– Route DiscoveryAODV– Route Discovery◦ Source Node broadcast RouteRequest

packet◦ Each intermediate node gets a

RouteRequest do the following steps: Establish a reverse link to node it received the

RouteRequest from If request received before discard If route to destination is available and up-to-date

return RouteReply using the reverse link Otherwise rebroadcast the RouteRequest

◦ Destination node respond with RouteReply using the reverse link

AODV - Route DiscoveryAODV - Route Discovery

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RouteRequest


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RouteRequestReverse Path Setup


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RouteReply


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Reverse Path Setup

RouteReplyForward Route Setup

AODV – Route AODV – Route MaintenanceMaintenanceWhen a node detects a link

failure, it sends special RouteReply with infinity distance

RouteReply is propagated to source node

Source node initiates a new RouteRequest

AODV – Route MaintenanceAODV – Route Maintenance

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RouteReply

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AODV ConcernsAODV ConcernsRoute Reply from intermediate

nodes can lead to inconstant routes Stale Cache

Periodic beaconing cost

Location Aided Routing Location Aided Routing (LAR)(LAR)Reduce the routing overhead in the

networkSource node flood the request to

certain area where it last heard from the destination

For the first time, it uses normal flood mechanism broadcast to all locations

GPS is required

LARLAR Expected Zone: The region that

may contain the destination based on its previous location, speed and time.

Request Zone: The region that RouteRequest packet are allowed to propagate to reach the destination

LARLAR Two Scheme:

1. Flood the RouteRequest into the request zone only to reach the destination in the expected zone

2. Stores the coordinates in the route request packets, the packets can only travel in the direction where the relative distance to the destination becomes smaller

LARLAR Destination: once receive

RouteRequest from the source, it sends RouteReply with its location and time stamp

Relative Distance Micro-Relative Distance Micro-Discovery ad hoc Discovery ad hoc routing(RDMAR)routing(RDMAR)Reduce the routing overhead in the

networkMinimize the flooding effect by limiting

route request to certain number of hopsUsed in Route Construction and

MaintenanceNo need for GPSAt the first time it works like normal

flooding operation Route discovery will have global effect

Light Wight Mobile Routing Light Wight Mobile Routing (LMR)(LMR)Destination rooted Directed

Acyclic Graph Based of link reversals protocol

Multiple route to the destination ◦no need to initiate another

RouteRequest unless all routes failed ◦Less Overhead

Good for routing in moderate mobile network

LMR– Route DiscoveryLMR– Route Discovery◦Every node is aware of its neighbors ◦Once RouteRequest received by one

of the destinstion neighbors it sends RouteReply

◦As the RouteReply packet traverse back to the source node, DAG is constructed

LMR - Route RequestLMR - Route Request

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LMR - Route ReplyLMR - Route Reply

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•As the RouteReply Packet traverse to the source the unsigned links become directed towards the destination

•S has many routes to D

LMR – Route MaintenanceLMR – Route MaintenanceTriggered, when the last route to the

destination is lost Node around the broken links inform

its upstream neighbor using RouteError packet

The packet informs the neighbors that no valid route exists anymore through the node to the destination

If the upstream neighbor has a route to the destination it sends Routeply packet, the links adjusted

LMR - Route MaintenanceLMR - Route Maintenance

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Route Error

LMR - Route MaintenanceLMR - Route Maintenance

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LMR – ConcernsLMR – ConcernsUnlimited time to recover from

network partitioning proposal for TORA

Temporally Ordered Routing Algorithm Temporally Ordered Routing Algorithm (TORA)(TORA)

Like LMR based on Link Reversal Algorithms

Solve LMR problem in case of Network partitions by limiting the route maintenance packets to a small region

Adopt the height metricsRequires time synchronization

TORA – Route DiscoveryTORA – Route DiscoverySource broadcast RouteRequest to

the destination Destination sets it height to zero and

transmit an RouteReply packetEach node along the way to the

source increase its height by one and rebroadcasts the RouteReply Packet with its updated heights

TORA - Route RequestTORA - Route Request

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TORA - Route ReplyTORA - Route Reply

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Height = 0

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Height = 1

Height = 2

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Height = 3

TORA – Route TORA – Route MaintenanceMaintenance

Triggered when the last link towards the destination is lost

Adjust Height Level and propagate through the network

Links are reversed to reflect the change

Route Deletion is flooded to delete invalid routes

Ant Colony Based Routing Ant Colony Based Routing Protocols (ARA)Protocols (ARA)

Adopt natural exampleWhen ants look for food, they leave transient

trail on the path for others to followForwarding ANT (RouteRequest) calculates a

pheromone value at each hopOnce destination is reached, Backward ANT

(RouteReply) traverse back to the sourceData packet traverse along the path increase

pheromone valuePheromone value of other unused path will

decrease until path is expired

ComparisonComparisonProtocol Routes Route Selection BeaconDSR Multiple Shortest Path NoARB Single Link Stability YesSSA Single Signal Strength YesAODV Single Shortest Path,

FreshnessYes

LAR Multiple Shortest Path NoRDMAR Single Shortest Path NoLMR-TORA Multiple Link reversal NoARA Multiple Shortest Path No

ComparisonComparisonProtocol Maintenance Special Needs Route

Discovery

DSR Global, notify source GlobalARB Local, bypass broken

linkGlobal

SSA Global, notify source GlobalAODV Global, notify source GlobalLAR Global, notify source GPS LocalizedRDMAR Global, notify source LocalizedLMR-TORA Link reversal Time Sync GlobalARA Back track until route

is found Global

reactive routing protocols for ad hoc mobile wireless networks

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