CBRP: A Cluster-based Routing Protocol for Mobile Ad hoc Networks Presented by: Jiang Mingliang Supervised by: Dr Y.C. Tay, Dr Philip Long

Presentation Outline zProject Overview and Objectives zRelated Works zCBRP: Motivations zCBRP: the Details zPerformance Evaluation zConclusion and Future Work

Project Overview zMobile Ad hoc Networks (MANET), its applications and challenges zIETF working group MANET

Project Overview zMANET characteristics ( & the difficulties for routing protocols) yDynamic Topology yLimited Link Bandwidth yLimited Power Supply for Mobile Node yNeed to scale to large networks

Project Objective zDesign a routing protocol for MANET that is: yefficient yscalable ydistributed and simple to implement zEvaluate CBRP through simulation ycompare with different design alternatives ycompare against other MANET protocols

Related Works zExisting MANET protocols: MANET routing protocols discover routes on-demand (re-active) Maintain updated routes (pro-active) Source routing Table driven Variation of distant vector? Variations of link state routing? DSR AODV, ABR, TORA DSDV OLSR

Related Works zProblems with pro-active routing protocols yhigh overhead in periodic/triggered routing table updates ylow convergence rate ywaste in maintaining routes that are not going to be used!! 7Simulating results have shown RIP, OSPF, DSDV fails to converge in highly dynamic MANET.

Related Works zRe-active Routing Protocols yprohibitive flooding traffic in route discovery yroute acquisition delay x every route breakage causes a new route discovery zWorks in trying to reduce flooding traffic yLAR (GPS for every mobile node?) yDSR (aggressive caching)

CBRP: Motivations zDesign Objective: a distributed, efficient, scalable protocol zMajor design decisions: yuse clustering approach to minimize on- demand route discovery traffic yuse “local repair” to reduce route acquisition delay and new route discovery traffic ysuggest a solution to use uni-directional links

CBRP: Protocol Overview

Cluster Formation Mechanism: Variations of “min-id” cluster formation algorithm. Nodes periodically exchange HELLO pkts to ymaintain a neighbor table xneighbor status (C_HEAD, C_MEMBER, C_UNDECIDED) xlink status (uni-directional link, bi-directional link) ymaintain a 2-hop-topology link state table Objective: Form small, stable clusters with only local information HELLO message format:

Cluster Formation (an example) zVariation of Min-ID yMinimal change yDefine Undecided State yAggressive Undecided -> Clusterhead e.g. 2’s neighbor table

Adjacent Cluster Discovery Objective: For clusterheads 3 hops away to discover each other Mechanism: Cluster Adjacency Table exchanged in HELLO message e.g. 4’s Cluster Adjacency Table

Route Discovery Source S “floods” all clusterheads with Route Request Packets (RREQ) to discover destination D [3] [3,1,8,11] (S) 11 (D) [3,1] [3,1,6] [3,1,8]

Route Reply zRoute reply packet (RREP) is sent back to source along reversed “loose source route” of clusterheads. zEach clusterhead along the way incrementally compute a hop-by-hop strict source route (S) 11 (D) the reversed loose source route of RREP: [11,8,1,3] [11] [11,9] [11,9,4] [11,9,4,3] the computed strict source route of 3->11 is: [11,9,4,3] [11,9,4]

Route Reply zRoute reply packet (RREP) is sent back to source along reversed “loose source route” of clusterheads. zEach clusterhead along the way incrementally compute a hop-by-hop strict source route (S) 11 (D) the reversed loose source route of RREP: [11,8,1,3] the computed strict source route of 3->11 is: [11,9,4,3]

Route Error Detection (S) 11 (D) zUse source routing for actual packet forwarding zA forwarding node sends a Route Error Message (ERR) to packet source if the next hop in source route is unreachable Source route header of data packet: [3,4,9,11] Route error (ERR) down link: {9->11}

Local Route Repair in CBRP zObjective yIncrease Packet Delivery Ratio ySave Route Rediscovery flooding traffic yReduce overall route acquisition delay zMechanism ySpatial Locality

Local Route Repair (S) 11 (D) zA forwarding node repairs a broken route using its 2-hop-topology information and modifies source route header accordingly. zDestination node sends a gratuitous route reply to inform source of the modified route Source route header of data packet: [3,4,9,11] Route error (ERR) down link: {9->11}

Local Route Repair (S) 11 (D) zA forwarding node repairs a broken route using its 2-hop-topology information and modifies source route header accordingly. zDestination node sends a gratuitous route reply to inform source of the modified route Source route header of data packet: [3,4,9,11] Modified source route [3,4,9,8,11]

Local Route Repair (S) 11 (D) zA forwarding node repairs a broken route using its 2-hop-topology information and modifies source route header accordingly. zDestination node sends a gratuitous route reply to inform source of the modified route Source route header of data packet: [3,4,9,11] Gratuitous route reply [3,4,9,8,11]

Utilize Unidirectional links zCause of unidirectional links yHidden Terminal yDifference in transmitter power or receiver sensitivity. zPitfalls with unilinks yDiscovery of (dead) unilinks yProblems with RTS/CTS/Snd/Ack, ARP

Utilize Unidirectional links zSelective use of Unilinks in CBRP

Supercluster zTaking advantage of hidden stability from the changing topology zBetter support for natural mobility patterns zMerge stable clusters into supercluster zto be further studied

Performance Evaluation zGoals yshow the robustness of CBRP’s packet delivery with reduced overhead. yevaluate how CBRP scales to larger networks ycompare different design alternatives (with/without local repair) ycompare CBRP with other MANET routing protocols zTools yns (network simulator) with wireless extension. yfeatures xmodels Lucent WaveLAN DSSS radio with signal attenuation, collision and capture. ximplements IEEE link layer

Simulation Environment zMobility Model (random way-point) yNodes move within a fixed rectangular area m x n yEach node chooses a random destination and move toward it at a speed uniformly distributed between 0 and max_speed yWhen reaching its destination, a node pauses for pause_time before start moving again. zTraffic Model yA node creates a session with a randomly selected destination node. yPackets of fixed size 128 byte are sent with constant sending rate of 4 pkts/sec

Simulation Parameters zSimulator parameters zCBRP implementation parameters

1. Packet delivery ratio with respect to network mobility zNetwork mobility is directly affected by pause_time. zpause_time has value {0, 30s, 60s, 120s, 300s, 600s} with 0 representing constant mobility and 600s signifying a stationary network.

2. Packet delivery ratio with respect to network size zSimulated network of nodes {25, 50, 75, 100, 150} with constant mobility, 60% of nodes have active CBR sessions.

2. Routing Overhead with respect to network size Routing overhead(normalized) = #routing pkts sent/ #data pkts delivered.

Milestones zAug 98, CBRP as Internet Draft zAug 98, in Chicago Presentation to the IETF zOct 98, presentation to MMlab, EE, NUS zNov 98, Presentation to IETF in Orlando zMar 99, paper submitted to Globecom99

Limitations of CBRP zSource Routing, overhead bytes per packet zClusters small, 2 levels of hierarchy, scalable to an extend

Conclusion zCBRP is a robust/scalable routing protocol superior to the existing proposals zFurther study on Superclustering zQoS, Multicast support in CBRP