A Seminar On MANET (Mobile Ad-hoc Network)

By: ANKUR KAUSHIK (MNW-883-2K11)RAHUL KUMAR (MNW-893-2K11)A Seminar On MANET(Mobile Ad-hoc Network)Types of Wireless NetworksInfrastructure based(Cellular Network).

Infrastructure less Network(Mobile Ad hoc Network) (MANET)(Ad hoc networks are defined as the category of wireless networks that utilize multi hop radio relaying and are capable of operating without the support of ant fix Infrastructure)2/14/2012SIT,IITKGP2

Why Ad Hoc Networks ?4Ease of deployment

Speed of deployment

Decreased dependence on infrastructureCharacteristics of an Ad-hoc networkCollection of mobile nodes forming a temporary networkNetwork topology changes frequently and unpredictablyNo centralized administration or standard support servicesHost is also function as router

2/14/2012SIT,IITKGP5Applications6Personal area networkingcell phone, laptop, ear phone, wrist watchMilitary environmentssoldiers, tanks, planesCivilian environmentstaxi cab networkmeeting roomssports stadiumsboats, small aircraftEmergency operationssearch-and-rescuepolicing and fire fighting

Many Variations7Fully Symmetric Environmentall nodes have identical capabilities and responsibilities

Asymmetric Capabilitiestransmission ranges and radios may differ battery life at different nodes may differprocessing capacity may be different at different nodesspeed of movement

Asymmetric Responsibilitiesonly some nodes may route packets some nodes may act as leaders of nearby nodes (e.g., cluster head)Issues In Ad Hoc NetworkMedium access schemeRoutingTransport Layer protocolPricing SchemeSelf OrganizationSecurityEnergy ManagementAddressing and service discoveryScalabilityMedium access schemeHidden TerminalExposed TerminalThroughputAccess delayFairnessAdaptive data rate control

RoutingMobilityBandwidthError prone and shared channelLocation dependent contentionQuick route reconfigurationLoop free routingMinimum control overheadMulticastingEfficiencyEfficient group managementSecurity

Transport Layer protocols

Pricing Scheme

Self OrganizationSecurityDenial ServiceResource ConsumptionEnergy DepletionBuffer FlowHost ImpersonationInformation DisclosureInterference

Why is Routing Different in Ad Hoc ???Host mobilityDynamic topologylink failure/repair due to mobility Distributed EnvironmentBandwidth constrainedEnergy constrained2/14/2012SIT,IITKGP14Categorization of Ad-Hoc Routing Protocols

Source Initiated On demand routing protocolReactive.on-demand style: create routes only when it is desired by the source nodeWhen a node requires a route to a destination, it initiates a route discovery process Route is maintained until destination becomes unreachable, or source no longer is interested in destination.

2/14/2012SIT,IITKGP16Table Driven Routing ProtocolProactive.Each node maintains one or more tables containing routing information to every other node in the network.Tables need to be consistent and up-to-date view of the network.Updates propagate through the network

2/14/2012SIT,IITKGP17Table Driven Routing Protocol2/14/2012SIT,IITKGP18Destination-Sequenced Distance Vector Protocol (DSDV)Basic Routing Protocol Based on Bellman ford routing algorithm with some improvementEach node maintains a list of all destinations and number of hops to each destination.Each entry is marked with a sequence number.Periodically send table to all neighbors to maintain topologyTwo ways to update neighbors:Full dumpIncremental update

2/14/2012SIT,IITKGP19Example of DSDV

Destination Next HopDistanceSequence NumberAA0S304_ABD3S424_BCC1S297_CDD1S687_DED2S868_EFD2S164_FDestination Next HopDistanceSequence NumberAA0S205_ABB1S334_BCC1S198_CDD1S567_DED2S767_EFD2S45_FAs Routing Table Before ChangeAs Routing Table After Change2/14/2012SIT,IITKGP20Advantages & Disadvantages of DSDVAdvantages:Less Delay to find routeExisting wired network protocol adaptableMaintain up-to-date view of network

Disadvantages:Excessive control overhead.Waiting time is Higher.Cluster-Head Gateway Switch Routing (CGSR)Uses DSDV as an underlying protocol and Least Cluster Change (LCC) clustering algorithmA clusterhead is able to control a group of ad-hoc hostsEach node maintains 2 tables:-A cluster member table, containing the cluster head for each destination node-A DV-routing table, containing the next hop to the destinationThe routing principle:Lookup of the clusterhead of the destination nodeLookup of next hopPacket send to destinationDestination cluster-head delivers packet

Cluster-head Gateway Switch Routing (CGSR)

Advantages & Disadvantages of(CGSR)Advantages:Hierarchical scheme enables partial coordinationBetter bandwidth utilizationDisadvantages:Too frequent cluster head selection can be an overhead and cluster nodes and Gateway can be a bottleneck Increase the path lengthGateway conflictsWireless Routing Protocol (WRP)Predecessor to destination (next to last hop) in the shortest path usedEliminates the Count-to-infinity problem and converges fasterNeighbor connectivity via periodic Hello messagesUpdate messages sent upon detecting a change in neighbor linkWireless Routing Protocol (WRP)Each node i maintains a Distance table (iDjk), Routing table (Destination Identifier, Distance iDj , Predecessor Pj ,the successor Sj), link cost table (Cost, Update Period) Processing Updates and creating Route TableUpdate from k causes i to re-compute the distances of all paths with k as the predecessorFor a destination j, a neighbor p is selected as the successor if p->j does not include i, and is the shortest path to j OperationJKIB(0, J)(2, K)(2, K)(1, K)X11101510(, K)(10, B)(10, I)(11, B)Comparisons of the Characteristics of Table-Driven Routing Protocols

Source Initiated On demand routing protocol2/14/2012SIT,IITKGP29Dynamic Source Routing (DSR) 30When node S wants to send a packet to node D, but does not know a route to D, node S initiates a route discovery

Source node S floods Route Request (RREQ)

Each node appends own identifier when forwarding RREQ

Route Discovery in DSR31BASEFHJDCGIK Node H receives packet RREQ from two neighbors: potential for collisionZYMNL[S,E][S,C]Route Discovery in DSR32BASEFHJDCGIK Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ onceZYMNL[S,C,G][S,E,F]Route Discovery in DSR33BASEFHJDCGIKZYM Nodes J and K both broadcast RREQ to node D Since nodes J and K are hidden from each other, their transmissions may collide NL[S,C,G,K][S,E,F,J]Route Discovery in DSR34BASEFHJDCGIKZY Node D does not forward RREQ, because node D is the intended target of the route discoveryMNL[S,E,F,J,M]Route Discovery in DSR35Destination D on receiving the first RREQ, sends a Route Reply (RREP)

RREP is sent on a route obtained by reversing the route appended to received RREQ

RREP includes the route from S to D on which RREQ was received by node DRoute Reply in DSR36BASEFHJDCGIKZYMNLRREP [S,E,F,J,D]Represents RREP control messageRoute Reply in DSR37Route Reply can be sent by reversing the route in Route Request (RREQ) only if links are guaranteed to be bi-directionalTo ensure this, RREQ should be forwarded only if it received on a link that is known to be bi-directional

If unidirectional (asymmetric) links are allowed, then RREP may need a route discovery for S from node D Unless node D already knows a route to node SIf a route discovery is initiated by D for a route to S, then the Route Reply is piggybacked on the Route Request from D.

If IEEE 802.11 MAC is used to send data, then links have to be bi-directional (since Ack is used)Dynamic Source Routing (DSR)38Node S on receiving RREP, caches the route included in the RREP

When node S sends a data packet to D, the entire route is included in the packet headerhence the name source routing

Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwardedData Delivery in DSR39BASEFHJDCGIKZYMNLDATA [S,E,F,J,D]Packet header size grows with route lengthDSR Optimization: Route Caching40Each node caches a new route it learns by any meansWhen node S finds route [S,E,F,J,D] to node D, node S also learns route [S,E,F] to node FWhen node K receives Route Request [S,C,G] destined for node, node K learns route [K,G,C,S] to node SWhen node F forwards Route Reply RREP [S,E,F,J,D], node F learns route [F,J,D] to node DWhen node E forwards Data [S,E,F,J,D] it learns route [E,F,J,D] to node DA node may also learn a route when it overhears Data packetsUse of Route Caching41When node S learns that a route to node D is broken, it uses another route from its local cache, if such a route to D exists in its cache. Otherwise, node S initiates route discovery by sending a route request

Node X on receiving a Route Request for some node D can send a Route Reply if node X knows a route to node D

Use of route cache can speed up route discoverycan reduce propagation of route requestsUse of Route Caching42BASEFHJDCGIK[P,Q,R] Represents cached route at a node (DSR maintains the cached routes in a tree format)MNL[S,E,F,J,D][E,F,J,D][C,S][G,C,S][F,J,D],[F,E,S][J,F,E,S]ZUse of Route Caching:Can Speed up Route Discovery43BASEFHJDCGIKZMNL[S,E,F,J,D][E,F,J,D][C,S][G,C,S][F,J,D],[F,E,S][J,F,E,S]RREQWhen node Z sends a route requestfor node C, node K sends back a routereply [Z,K,G,C] to node Z using a locallycached route[K,G,C,S]RREPUse of Route Caching:Can Reduce Propagation of Route Requests44BASEFHJDCGIKZYMNL[S,E,F,J,D][E,F,J,D][C,S][G,C,S][F,J,D],[F,E,S][J,F,E,S]RREQAssume that there is no link between D and Z.Route Reply (RREP) from node K limits flooding of RREQ.In general, the reduction may be less dramatic.[K,G,C,S]RREPRoute Error (RERR)45BASEFHJDCGIKZYMNLRERR [J-D]J sends a route error to S along route J-F-E-S when its attempt to forward the data packet S (with route SEFJD) on J-D fails

Nodes hearing RERR update their route cache to remove link J-DRoute Caching: Beware!46Stale caches can adversely affect performance

With passage of time and host mobility, cached routes may become invalid

A sender host may try several stale routes (obtained from local cache, or replied from cache by other nodes), before finding a good route

An illustration of the adverse impact on TCP will be discussed later in the tutorial [Holland99]Ad Hoc On-Demand Distance Vector Routing (AODV) 47DSR includes source routes in packet headers

Resulting large headers can sometimes degrade performanceparticularly when data contents of a packet are small

AODV attempts to improve on DSR by maintaining routing tables at the nodes, so that data packets do not have to contain routes

AODV retains the desirable feature of DSR that routes are maintained only between nodes which need to communicateAODV48Route Requests (RREQ) are forwarded in a manner similar to DSR

When a node re-broadcasts a Route Request, it sets up a reverse path pointing towards the sourceAODV assumes symmetric (bi-directional) links

When the intended destination receives a Route Request, it replies by sending a Route Reply

Route Reply travels along the reverse path set-up when Route Request is forwardedRoute Requests in AODV49BASEFHJDCGIKZYRepresents a node that has received RREQ for D from SMNLRoute Requests in AODV50BASEFHJDCGIKRepresents transmission of RREQZYBroadcast transmissionMNLRoute Requests in AODV51BASEFHJDCGIK Represents links on Reverse PathZYMNLReverse Path Setup in AODV52BASEFHJDCGIK Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ onceZYMNLReverse Path Setup in AODV53BASEFHJDCGIKZYMNLReverse Path Setup in AODV54BASEFHJDCGIKZY Node D does not forward RREQ, because node D is the intended target of the RREQMNLRoute Reply in AODV55BASEFHJDCGIKZYRepresents links on path taken by RREP MNLRoute Reply in AODV56An intermediate node (not the destination) may also send a Route Reply (RREP) provided that it knows a more recent path than the one previously known to sender S

To determine whether the path known to an intermediate node is more recent, destination sequence numbers are used

The likelihood that an intermediate node will send a Route Reply when using AODV not as high as DSRA new Route Request by node S for a destination is assigned a higher destination sequence number. An intermediate node which knows a route, but with a smaller sequence number, cannot send Route ReplyForward Path Setup in AODV57BASEFHJDCGIKZYMNLForward links are setup when RREP travels alongthe reverse path

Represents a link on the forward pathData Delivery in AODV58BASEFHJDCGIKZYMNLRouting table entries used to forward data packet.

Route is not included in packet header.DATAData Delivery in AODV59BASEFHJDCGIKZYMNLRouting table entries used to forward data packet.

Route is not included in packet header.DATATimeouts60A routing table entry maintaining a reverse path is purged after a timeout intervaltimeout should be long enough to allow RREP to come back

A routing table entry maintaining a forward path is purged if not used for a active_route_timeout intervalif no is data being sent using a particular routing table entry, that entry will be deleted from the routing table (even if the route may actually still be valid)Link Failure Reporting61A neighbor of node X is considered active for a routing table entry if the neighbor sent a packet within active_route_timeout interval which was forwarded using that entry

When the next hop link in a routing table entry breaks, all active neighbors are informed

Link failures are propagated by means of Route Error messages, which also update destination sequence numbersRoute Error62When node X is unable to forward packet P (from node S to node D) on link (X,Y), it generates a RERR message

Node X increments the destination sequence number for D cached at node X

The incremented sequence number N is included in the RERR

When node S receives the RERR, it initiates a new route discovery for D using destination sequence number at least as large as NDestination Sequence Number63Continuing from the previous slide

When node D receives the route request with destination sequence number N, node D will set its sequence number to N, unless it is already larger than NLink Failure Detection64Hello messages: Neighboring nodes periodically exchange hello message

Absence of hello message is used as an indication of link failure

Alternatively, failure to receive several MAC-level acknowledgement may be used as an indication of link failureWhy Sequence Numbers in AODV65To avoid using old/broken routesTo determine which route is newer

To prevent formation of loops

Assume that A does not know about failure of link C-D because RERR sent by C is lostNow C performs a route discovery for D. Node A receives the RREQ (say, via path C-E-A)Node A will reply since A knows a route to D via node BResults in a loop (for instance, C-E-A-B-C )ABCDEWhy Sequence Numbers in AODV66Loop C-E-A-B-C

ABCDEOptimization: Expanding Ring Search67Route Requests are initially sent with small Time-to-Live (TTL) field, to limit their propagationDSR also includes a similar optimization

If no Route Reply is received, then larger TTL triedSummary: AODV68Routes need not be included in packet headers

Nodes maintain routing tables containing entries only for routes that are in active use

At most one next-hop per destination maintained at each nodeDSR may maintain several routes for a single destination

Unused routes expire even if topology does not changeTemporally OrderedRouting Algorithm (TORA)Link reversal algorithmDestination oriented Directed Acyclic Graph (DAG)Full/Partial reversal of linksAssigns a reference level (height) to each nodeAdjust reference level to restore routes on link failureMultiple routes to destination; route optimality not importantQuery, Update, Clear packets used for creating, maintaining and erasing routes Creating RoutesCABEG (DEST)FHDQRYQRYQRYUPDQRYQRYUPDUPDUPDUPDUPDUPDRoute MaintenanceCABEG (DEST)FHDUPDXUPDUPDPerformance AnalysisSimulation EnvironmentNetwork Simulator, 50 nodes in a 1500x300m rectangular flat gridRandom waypoint mobility (Average 10 m/sec)Constant bit rate traffic (UDP)Address resolution : ARP implementation in BSD UnixMedium Access Control : IEEE 802.11 Physical Layer model : combines both free space and two ray ground reflection modelProtocols studied : DSDV(SQ), AODV-LL, DSR, TORAPerformance AnalysisMetricsPacket Delivery Ratio : Ratio of number of packets generated by CBR sources to that received by CBR sinks at destinationRouting Overhead : number of routing packets sent; each transmission counts as one transmissionPath Optimality : Difference between length of actual path took and the length of the shortest pathPacket Delivery Ratio95-100% in most cases for DSR, AODVStale route entries in DSDV cause dropsShort lived loops in TORA as part of link reversalAll protocols perform well when there is low node mobility +

Routing Overhead (packets)Route caching and non-propagating RREQs in DSRTORASum of mobility dependant, independent overhead for TORACongestive collapse Nearly constant for DSDV due to periodic updates

Routing Overhead (Bytes)DSR more expensive than AODV except at high mobilitySmaller packets in AODV, may be more expensive in terms of media access, power and network utilization

Path OptimalityDSDV, DSR use routes close to optimalTORA not designed to find shortest pathTORA, AODV use paths close to optimum when node mobility is low

Comparisons of the Characteristics of Source Initiated On-Demand Ad-Hoc Routing Protocols

Comparisons of On-Demand versus Table-Driven Based Routing Protocols

ReferencesD. Baker, M. S. Corson, P. Sass, and S. Ramanatham, \Flat vs. Hierarchical Network Control Architecture," ARO/DARPA Workshop on Mobile Ad-Hoc Networking, http://www.isr.umd.edu/Courses/Workshops/MANET/program.html, March 1997.J. Broch, D. B. Johnson, D. A. Maltz, \The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks," IETF Internet Draft draft-ietf-manet-dsr-01.txt, December 1998 (Work in Progress).C.-C. Chiang, M. Gerla, and L. Zhang, \Adaptive Shared Tree Multicast in Mobile Wireless Networks," Proceedings of GLOBECOM '98, pp. 1817{1822, November 1998.C.-C. Chiang, H.K.Wu, W. Liu, and M. Gerla, \Routing in Clustered Multihop, Mobile Wireless Networks with Fading Channel," Proceedings of IEEE SICON'97, pp. 197{211, April 1997.M. S. Corson and A. Ephremides, \A Distributed Routing Algorithm for Mobile Wireless Networks," ACM/Baltzer Wireless Networks Jouornal, Vol. 1, No. 1, pp. 61{81, February 1995.R. Dube, C. D. Rais, K.-Y. Wang, and S.K. Tripathi, \Signal Stability based Adaptive Routing

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