CBRP : A C luster- b ased R outing P rotocol for Mobile Ad hoc Networks

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

2. Presentation Outline • Project Overview and Objectives • Related Works • CBRP: Motivations • CBRP: the Details • Performance Evaluation • Conclusion and Future Work

3. Project Overview • Mobile Ad hoc Networks (MANET), its applications and challenges • IETF working group MANET

4. Project Overview • MANET characteristics ( & the difficulties for routing protocols) • Dynamic Topology • Limited Link Bandwidth • Limited Power Supply for Mobile Node • Need to scale to large networks

5. Project Objective • Design a routing protocol for MANET that is: • efficient • scalable • distributed and simple to implement • Evaluate CBRP through simulation • compare with different design alternatives • compare against other MANET protocols

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

7. Related Works • 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!! • Simulating results have shown RIP, OSPF, DSDV fails to converge in highly dynamic MANET.

8. Related Works • 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)

9. CBRP: Motivations • Design Objective: a distributed, efficient, scalable protocol • Major design decisions: • use clustering approach to minimize on-demand route discovery traffic • use “local repair” to reduce route acquisition delay and new route discovery traffic • suggest a solution to use uni-directional links

10. CBRP: Protocol Overview

11. 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:

12. 11 8 9 4 10 3 1 2 7 5 6 Cluster Formation (an example) • Variation of Min-ID • Minimal change • Define Undecided State • Aggressive Undecided -> Clusterhead e.g. 2’s neighbor table

13. 11 8 9 4 10 3 1 2 7 5 6 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

14. [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]

15. 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]

16. 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]

17. 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}

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

19. 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}

20. 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]

21. 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

22. 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

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

24. Supercluster • Taking advantage of hidden stability from the changing topology • Better support for natural mobility patterns • Merge stable clusters into supercluster • to be further studied

25. Performance Evaluation • Goals • show the robustness of CBRP’s packet delivery with reduced overhead. • evaluate how CBRP scales to larger networks • compare different design alternatives (with/without local repair) • compare CBRP with other MANET routing protocols • Tools • ns (network simulator) with wireless extension. • features • models Lucent WaveLAN DSSS radio with signal attenuation, collision and capture. • implements IEEE 802.11 link layer

26. Simulation Environment • Mobility Model(random way-point) • Nodes move within a fixed rectangular area m x n • Each node chooses a random destination and move toward it at a speed uniformly distributed between 0 and max_speed • When reaching its destination, a node pauses for pause_timebefore start moving again. • Traffic Model • A node creates a session with a randomly selected destination node. • Packets of fixed size 128 byte are sent with constant sending rate of 4 pkts/sec

27. Simulation Parameters • Simulator parameters • CBRP implementation parameters

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

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

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

31. Milestones • Aug 98, CBRP as Internet Draft • Aug 98, in Chicago Presentation to the IETF • Oct 98, presentation to MMlab, EE, NUS • Nov 98, Presentation to IETF in Orlando • Mar 99, paper submitted to Globecom99

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

33. Conclusion • CBRP is a robust/scalable routing protocol superior to the existing proposals • Further study on Superclustering • QoS, Multicast support in CBRP