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CBRP: A Cluster-based Routing Protocol for Mobile Ad hoc Networks

CBRP: A Cluster-based Routing Protocol for Mobile Ad hoc Networks. Dr. R. B. Patel. Existing MANET protocols:. Hybrid . discover routes within a zone Proactive and zone to zone Reactive. Table driven within zone. ZRP. discover routes on-demand ( reactive ). Source routing. DSR.

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CBRP: A Cluster-based Routing Protocol for Mobile Ad hoc Networks

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  1. CBRP: A Cluster-based Routing Protocol for Mobile Ad hoc Networks Dr. R. B. Patel

  2. Existing MANET protocols: Hybrid discover routes within a zone Proactive and zone to zone Reactive Table driven within zone ZRP discover routes on-demand (reactive) Source routing DSR Table driven AODV, ABR, TORA MANET routing protocols Variation of distant vector? DSDV Maintain updated routes (proactive) OLSR Variations of link state routing?

  3. Continue… • Problems with pro-active routing protocols • high overhead in • periodic/triggered routing table updates • low convergence rate • waste in maintaining routes that are not going to be used!! • DSDV fails to converge in highly dynamic MANET.

  4. Continue… • Re-active Routing Protocols • prohibitive flooding traffic in route discovery • route acquisition delay • every route breakage causes a new route discovery • Works in trying to reduce flooding traffic • LAR (GPS for every mobile node?) • DSR (aggressive caching)

  5. Why Cluster Based Routing Protocol (CBRP)? • It is a distributed, efficient, scalable protocol • It • uses clustering approach to minimize on-demand route discovery traffic • uses “local repair” to reduce route acquisition delay and new route discovery traffic • suggests a solution to use uni-directional links

  6. Continue … • Non-uniform (partitioning) • Clusters may be overlapping or disjoint • Elected cluster heads may not be adjacent • Topology-based • Exchange 2-hop topology to define clusters • Inform cluster head of Gateways nodes • Cluster head knows all clusters eventually • Reactive protocol • Forward RREQ to cluster head when no known route • Broadcast to other cluster heads via gateway nodes • Intermediate cluster heads optimizes route in RREP • Routes need not pass through cluster heads

  7. Cluster head Gateway Switch Routing (CGSR) • All nodes within a cluster communicate with a cluster head • Routing uses a hierarchical cluster head-to-gateway approach

  8. Continue … • Multi-channel • Low level MAC layer protocol • Non-uniform (Partitioning) • Elected cluster head • Each node maintains • Cluster table • Routing table • Distance-based, Reactive protocol • DSDV as underlying routing scheme • Packet routes from cluster head to gateways nodes and so on till destination. • Broadcast cluster member tables periodically

  9. Continue …

  10. Core-Extraction Distributed Ad Hoc Routing (CEDAR) • A subset of nodes in the network is identified as the core • Each node in the network must be adjacent to at least one node in the core • Each core node determines paths to nearby core nodes by means of a localized broadcast

  11. Continue … A G D H B C E F S J K Node E is the dominator for nodes D, F and K A core node

  12. Why Cluster Based Routing Protocol (CBRP): Protocol Overview

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

  14. Cluster Formation (an example) • Variation of Min-ID • Minimal change • Define Undecided State • Aggressive Undecided -> Clusterhead e.g. 2’s neighbor table 11 8 9 4 10 3 1 2 7 5 6

  15. 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 11 8 9 4 10 3 1 2 7 5 6

  16. [3,1,8,11] 11 (D) 11 9 [3,1,8] 8 4 10 3 3 (S) 1 [3,1] 2 7 6 5 [3,1,6] Route Discovery Source S “floods” all clusterheads with Route Request Packets (RREQ) to discover destination D [3]

  17. 11 (D) 11 [11] [11,9] 9 [11,9,4] 8 4 10 3 3 (S) [11,9,4,3] 1 [11,9,4] the computed strict source route of 3->11 is: [11,9,4,3] 2 7 6 5 Route Reply • Route reply packet (RREP) is sent back to source along reversed “loose source route” of clusterheads. • Each clusterhead along the way incrementally compute a hop-by-hop strict source route. the reversed loose source route of RREP: [11,8,1,3]

  18. 11 (D) 11 9 8 4 10 3 (S) 3 1 2 7 6 5 Route Reply • Route reply packet (RREP) is sent back to source along reversed “loose source route” of clusterheads. • Each clusterhead along the way incrementally compute a hop-by-hop strict source route. the reversed loose source route of RREP: [11,8,1,3] the computed strict source route of 3->11 is: [11,9,4,3]

  19. 11 9 8 4 10 3 1 2 7 6 5 Route Error Detection • Use source routing for actual packet forwarding • A forwarding node sends a Route Error Message (ERR) to packet source if the next hop in source route is unreachable 11 (D) Source route header of data packet: [3,4,9,11] 3 (S) Route error (ERR) down link: {9->11}

  20. Local Route Repair in CBRP • Objective • Increase Packet Delivery Ratio • Save Route Rediscovery flooding traffic • Reduce overall route acquisition delay • Mechanism • Spatial Locality

  21. 11 9 8 4 10 3 1 2 7 6 5 Local Route Repair • A forwarding node repairs a broken route using its 2-hop-topology information and modifies source route header accordingly. • Destination node sends a gratuitous route reply to inform source of the modified route 11 (D) Source route header of data packet: [3,4,9,11] 3 (S) Route error (ERR) down link: {9->11}

  22. 11 9 8 4 10 3 1 2 7 6 5 Local Route Repair • A forwarding node repairs a broken route using its 2-hop-topology information and modifies source route header accordingly. • Destination node sends a gratuitous route reply to inform source of the modified route 11 (D) Source route header of data packet: [3,4,9,11] 3 (S) Modified source route [3,4,9,8,11]

  23. Local Route Repair • A forwarding node repairs a broken route using its 2-hop-topology information and modifies source route header accordingly. • Destination node sends a gratuitous route reply to inform source of the modified route 11 (D) 11 Source route header of data packet: [3,4,9,11] 9 8 4 10 3 3 (S) 1 Gratuitous route reply [3,4,9,8,11] 2 7 6 5

  24. Utilize Unidirectional links • Cause of unidirectional links • Hidden Terminal • Difference in transmitter power or receiver sensitivity. • Pitfalls with unilinks • Discovery of (dead) unilinks • Problems with 802.11 RTS/CTS/Snd/Ack, ARP

  25. Utilize Unidirectional links • Selective use of Unilinks in CBRP 5 6 7 9 2 1 4 8 3 10

  26. Limitations of CBRP • Source Routing, overhead bytes per packet • Clusters small, 2 levels of hierarchy, scalable to an extend

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