Reactive Routing Protocols for Ad hoc Mobile Wireless Networks
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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
Elizabeth Royer and Chai Keong Toh, “A review of Current Routing Protocols for Ah Hoc Mobile Wireless Networks”, IEEE personal Communications April 1999
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
On-Demand Routing Protocols
Source Routing Hop-by-Hop Routing
ABR DSRAODV LARLMR RDMARSSA
TORA
Elizabeth Royer and Chai Keong Toh, “A review of Current Routing Protocols for Ah Hoc Mobile Wireless Networks”, IEEE personal Communications April 1999
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
On-Demand Routing Protocols
Source Routing Hop-by-Hop Routing
ABR DSRAODV LARLMR RDMARSSA
TORA
Elizabeth Royer and Chai Keong Toh, “A review of Current Routing Protocols for Ah Hoc Mobile Wireless Networks”, IEEE personal Communications April 1999
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
AODV - Route DiscoveryAODV - Route Discovery
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RouteRequestReverse Path Setup
AODV - Route DiscoveryAODV - Route Discovery
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RouteRequestReverse Path Setup
RouteRequest Dropped
AODV - Route DiscoveryAODV - Route Discovery
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RouteRequestReverse Path Setup
RouteReply
AODV - Route DiscoveryAODV - Route Discovery
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Reverse Path Setup
RouteReplyForward Route Setup
AODV - Route DiscoveryAODV - Route Discovery
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Reverse Path Setup
RouteReplyForward Route Setup
AODV - Route DiscoveryAODV - Route Discovery
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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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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
Height = 1
Height = 1
Height = 2
Height = 2
Height = 2
Height = 3
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