manets routing dr. raad s. al-qassas department of computer science psut [email protected]
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OutlineOutline
Routing challengesRouting challenges Mobility patternsMobility patterns AODV routing protocolAODV routing protocol Performance metricsPerformance metrics
MANET routing challengesMANET routing challenges
No fixed infrastructure.No fixed infrastructure. Nodes can have unlimited mobility.Nodes can have unlimited mobility. Multiple hops to destination.Multiple hops to destination. Unreliable communication medium.Unreliable communication medium. All nodes need to participate in routing/forwarding.All nodes need to participate in routing/forwarding.
Mobility patterns Mobility patterns
MANET nodes may follow one or more of the following MANET nodes may follow one or more of the following patterns :patterns :– Stationary nodes (e.g., sensor nodes).Stationary nodes (e.g., sensor nodes).– Highly mobile nodes (e.g., vehicles).Highly mobile nodes (e.g., vehicles).– Discrete versus continuous mobility.Discrete versus continuous mobility.– Structured versus unstructured mobility.Structured versus unstructured mobility.
Mobility patterns Mobility patterns
Node mobility is characterised by:Node mobility is characterised by: Speed.Speed. Direction.Direction. Pause time.Pause time.
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Unicast Route EstablishmentUnicast Route Establishment Unicast route Unicast route is a route from a source node to a is a route from a source node to a
destination node. destination node.
Ad hoc On-demand Distance Vector Ad hoc On-demand Distance Vector Routing (AODV)Routing (AODV)
AODV has two phases:AODV has two phases:– Route establishmentRoute establishment– Route maintenanceRoute maintenance
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Route Request (RREQ) MessageRoute Request (RREQ) Message When node When node S S wants to send a message to node wants to send a message to node DD, , S S
searches its route table for a route to searches its route table for a route to DD.. If there is no route, If there is no route, S S initiates a initiates a RREQ RREQ message with message with
the following components : the following components : – The The IP addresses IP addresses of of S S and and DD– The current sequence number of The current sequence number of S S and the last known and the last known
sequence number of sequence number of DD– A A broadcast ID broadcast ID from from S. S. This broadcast This broadcast ID ID is incremented is incremented
each time each time S S sends a sends a RREQ RREQ message.message.
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Processing a RREQ Message (I)Processing a RREQ Message (I) The The <broadcast ID, IP address> <broadcast ID, IP address> pair of the source pair of the source S S
forms a unique identifier for the RREQ. forms a unique identifier for the RREQ.
Suppose a node Suppose a node P P receives the receives the RREQ RREQ from from SS. . P P first first checks whether it has received this checks whether it has received this RREQ RREQ before. before.
Each node stores the Each node stores the <broadcast ID, IPaddress> <broadcast ID, IPaddress> pairs pairs for all the recent for all the recent RREQRREQs it has received. s it has received.
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Processing a RREQ Message (II)Processing a RREQ Message (II)
If If P P has seen this has seen this RREQ RREQ from from S S already, already, P P discards the discards the RREQRREQ. Otherwise, . Otherwise, P P processes the processes the RREQ : RREQ :
P P sets up a sets up a reverse route reverse route entry in its entry in its route table route table for the source for the source SS..
This entry contains the This entry contains the IP address IP address and and current sequence number current sequence number of of SS, , number of number of hops hops to to S S and the address of the neighbour from whom and the address of the neighbour from whom P P got the got the RREQRREQ..
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Lifetime of a Route-Table EntryLifetime of a Route-Table Entry A A lifetime lifetime is associated with the entry in the is associated with the entry in the route route
tabletable. .
This is an important feature of This is an important feature of AODVAODV. If a route entry . If a route entry is not used within the is not used within the specified lifetimespecified lifetime, it is deleted., it is deleted.
A route is A route is maintained maintained only when it is used. A route only when it is used. A route that is that is unused unused for a long time is assumed to be for a long time is assumed to be stalestale..
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Route Requests in AODVRoute Requests in AODV
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Represents a node that has received RREQ for D from S
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Route Requests in AODVRoute Requests in AODV
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Represents transmission of RREQ
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Route Requests in AODVRoute Requests in AODV
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Represents links on Reverse Path
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Reverse Path Setup in AODVReverse Path Setup in AODV
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• Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once
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Reverse Path Setup in AODVReverse Path Setup in AODV
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Reverse Path Setup in AODVReverse Path Setup in AODV
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• Node D does not forward RREQ, because node D is the intended target of the RREQ
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Forward Path Setup in AODVForward Path Setup in AODV
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Forward links are setup when RREP travels alongthe reverse path
Represents a link on the forward path
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Handling More than one RREPHandling More than one RREP
An intermediate node An intermediate node P P may receive more than one may receive more than one RREP RREP for the same for the same RREQRREQ..
P P forwards the first forwards the first RREP RREP it receives and forwards a it receives and forwards a second second RREP RREP later only if :later only if :– The later The later RREP RREP contains a greater sequence number for the contains a greater sequence number for the
destination, ordestination, or– The The hop-count hop-count to the destination is smaller in the later to the destination is smaller in the later
RREPRREP– Otherwise, it does not forward the later Otherwise, it does not forward the later RREPRREPs. This s. This
reduces the number of reduces the number of RREPRREPs propagating towards the s propagating towards the source. source.
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Route MaintenanceRoute Maintenance
Once a Once a unicast route unicast route has been established has been established between two nodes between two nodes S S and and DD, it is maintained as , it is maintained as long as long as S S (source node) needs the route. (source node) needs the route.
If If S S moves during an active session, it can reinitiate moves during an active session, it can reinitiate route discoveryroute discovery to establish a new route to to establish a new route to DD..
When When D D or an intermediate node moves, a or an intermediate node moves, a route route error (RERR) error (RERR) message is sent to message is sent to SS..
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Route MaintenanceRoute Maintenance
The link from node The link from node 3 3 to to D D is broken as is broken as 3 3 has moved away to a position has moved away to a position 3´.3´.
Node Node 2 2 sends a sends a RERR RERR message to message to 1 1 and and 1 1 sends the message in turn to sends the message in turn to SS. . S S initiates a initiates a route discovery route discovery if it still needs the route to if it still needs the route to DD..
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Updating Route TablesUpdating Route Tables
Suppose neighbours Suppose neighbours 4 4 and and 5 5 route through route through 2 2 to to reach reach DD. Node . Node 2 2 broadcasts broadcasts RERR RERR to all such to all such neighbours. neighbours.
Each neighbour marks its Each neighbour marks its route table route table entry to entry to D D as as invalid by setting the distance to invalid by setting the distance to infinityinfinity..
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Updating Route TablesUpdating Route Tables
Each neighbour in turn propagates the Each neighbour in turn propagates the RERRRERR message. message.
Route entries with an Route entries with an infinity infinity metric are not rejected metric are not rejected immediately as they contain useful routing immediately as they contain useful routing information for the neighbourhood. information for the neighbourhood.
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Local ConnectivityLocal Connectivity
Neighbourhood information is obtained through Neighbourhood information is obtained through hello messageshello messages. Each node broadcasts a . Each node broadcasts a hello hello message message to its neighbours at a regular to its neighbours at a regular hello-hello-interval. interval.
When a node When a node M M receives a receives a hello message hello message from a from a neighbour neighbour NN, node , node M M updates the updates the lifetime lifetime associated with associated with N N in its in its route table. route table.
Hello messages Hello messages propagate only for propagate only for one hop, one hop, in in the neighbourhood of a node. the neighbourhood of a node.
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Performance measuresPerformance measures
Throughput Throughput end-to-end delay end-to-end delay routing overheadrouting overhead
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Performance measuresPerformance measures (throughput) (throughput)
The throughput is the amount of data received (measured in bits per second) at the final destination over the simulated time averaged over the number of flows.
provides an indication of the efficiency of the routing protocol as it shows the amount of data that the protocol is able to deliver to destinations.
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Performance measuresPerformance measures (end-to-end delay ) (end-to-end delay )
The end-to-end delay is the average time interval between the generation of a packet in a source node and the successful delivery of the packet at the destination node.
This delay accounts for all possible delays that can occur in the source and all intermediate nodes.
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Performance measuresPerformance measures (routing overhead) (routing overhead)
The routing overhead is the number of routing (control) packets generated during the simulated time in order to establish and maintain paths and to exchange traffic information among network nodes as dictated by the operation of a given traffic aware metrics.
routing packets sent over multiple hops, each hop counts as one transmission.
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Performance measuresPerformance measures
The routing overhead measures the scalability of the routing protocol and its efficiency in terms of consuming a node’s battery power.
The high routing overhead could affect the performance in terms of data throughput and end-to-end delay.
The high overhead is a result of factors like the unsuccessful delivery of route requests and the unsuccessful delivery of route replies.