Dissertation DefenseOn-Demand Link-State Routing in      Ad-Hoc Networks            Soumya Roy       Computer Engineering,...
Presentation Outline   Wireless ad-hoc networks   On-demand link-state routing protocol       Source-tree On-demand Ada...
PART ONE    Wireless Ad Hoc       Networks
Wireless Ad Hoc Networks       WLAN                              Ad hoc NetworksNodes acts as sources, relays and destinat...
Challenges in Designing Routing        Protocols for Mobile Ad-Hoc Networks   Significant Packet Loss :       Fading, in...
Taxonomy of Routing Protocols   Proactive Routing (WRP, DSDV, OLSR,    STAR)       Maintains routes for all destinations...
Main goal is to ….Explore how link-state information can be      used efficiently for setting up          on-demand routes
Previous Work   Proactive link-state protocols       Source Tree Adaptive Routing (STAR)                      Exchanges...
PART TWO   On-Demand Link-    State Routing
Outline   Source Tree On-demand Adaptive    Routing (SOAR)   Challenges in the path selection   On-demand Link Vector R...
Source Tree On-demand Adaptive        Routing (SOAR)
What is Source Tree   Each node can build source tree based    on paths to all reachable destinations                    ...
What is a Minimal Source Tree   Contains paths to important nodes    (relays, potential relays, receivers)               ...
Construction of Topology Table                                                             i          x                   ...
Summary   Query, Reply for path discovery   Updates for path repair   ForcedUpdate, ForcedReply for forcing    nodes ad...
Performance Evaluation (ns2)   20 nodes   1000mx300m rectangular field   IEEE 802.11 MAC   Link layer notification of ...
Effect of Increasing Flows (pause=0s)
Effect of Mobility (10 flows)
Effect of Loading (10 flows)
Challenges of Path Selection in On-demand Link State Routing
Path Selection Algorithm                                                                   Links advertised by b          ...
Computing Source TreeOPT-TREE : Given a graph and a set oflabels corresponding to each link, whatis maximum size of the so...
Computing Source Tree (contd…)
Heuristic for Computing Source Tree   A polynomial time approximation (O(nd^2))    algorithm   Finding shortest valid pa...
Computing source graph (in SOAR)                            MBF           BF                       (a,d1) (x,d2)          ...
How does SOAR handle pathselection problem   Computes source graph   Exchanges source trees   Uses forced routing to co...
Next Step …….   Use of complete path information   Links in paths validated using sequence    numbers   Links merged to...
On-Demand Link Vector Protocol(OLIVE)
Overview of OLIVE   Route discovery       Setting up new paths       RREQ, RREP and RREPACK   Route Repair       Loca...
Use of path information in OLIVE
Use of path information (contd …)  c   e
RREQ                         d                a        RR          EQRREQi                                 j      k       ...
Example (Route Error and Repair)                                            j                     j                       ...
Properties of OLIVE   When cost of path can increase, inter-    neighbor synchronization is used       Predecessors rele...
Performance Evaluation (ns2)   50 nodes   1500x300m (range = 250m)   2Mbps DSSS radio interface   Random Waypoint mode...
Simulation Results (10 flows)Percentage Throughput   Total Control Packets
Simulation Results (10 flows)Optimality of routes   End to end delay
Effect of Packet Load (20 sources)Control packets sent   Percentage Delivery
Effect of Packet Load (20 sources)Optimality of routes   End-to-end Delay
Quantifying loopsPacket rate = 8 packets/s   Packet rate = 10 packets/s
Summary   Elaborately studied the problem of    using on-demand link-state information    for routing   Developed routin...
PART 2Node-Centric Hybrid Routing for      Ad Hoc Networks
Outline   Introduction   Reasons behind node-centric hybrid    routing   Methods and new protocols   Performance evalu...
Introduction   Practical scenarios for mobile ad-hoc    networks will have traffic between    mobile nodes and netmarks ...
Practical Ad Hoc Networks
Related Work in Hybrid Routing   Zone Routing Protocol (Haas & Pearlman)       Proactive routing within zones       Rea...
Why Node-centric Hybrid Routing   On Demand path creation towards netmarks       Each session set up leads to flooding, ...
Methods of Node-Centric HybridRouting    Prolonged Caching        Caching of netmark information for long         enough...
Protocols with Prolonged Caching   Route errors and route requests for netmarks    do not depend on traffic   AODV : lon...
Protocols With Proactive Netmark Routes1.       Nemarks advertise their presence          MAC layer sends beacons       ...
Protocols with Proactive Routes(contd…)3.       New paths to netmarks are always         advertised        Change 3 needs...
SOAR with Hybrid Functionality   SOAR performs better than both DSR or AODV   Modifications of SOAR to incorporate hybri...
Setting up paths in NEST            Forward paths are set up proactively         Reverse paths are set up by traffic flo...
Issues in Hybrid Routing   Forwarding of data packets       Use of subnet address for ad hoc networks   Multiple Netmar...
Performance Evaluation   Using ns2   Comparison of NEST, NOLR with DSR,    AODV and SOAR
Traffic and Mobility Models   Mobility Model : random waypoint model   Traffic Pattern       FLOW OFF/ON model       D...
Simulation Scenario 1   31 nodes   single netmark in the centre of a    rectangular field   (1000m x 500m) size   Rang...
Performance Evaluation (3 pkts/s)                    Percentage ThroughputControl packet
Performance Evaluation (5 pkts/s)Control packets   Percentage Throughput
Simulation Scenario 2   31 nodes    single netmark       Static       Mobile in a restricted region       Mobile thro...
Performance Evaluation
Simulation Scenario 3   31 nodes   Two static netmarks   To observe : can anycast route    discovery lead to any signif...
NEST                  A-SOAR                  NOLRPerformance Evaluation
Contributions   First detailed study on use of link-state    information on-demand   Developed two unique highly efficie...
Future Work   Opportunistic version of OLIVE to target    practical ad-hoc networks   Node-centric version targeting hug...
Acknowledgements   Thanks to JJ for being the greatest adviser   Thanks to Richard, Katia for being on my    defense com...
THE END
Publications   SOAR (IEEE Infocom 2001)   Heuristic for Source Tree Computation    (ICCCN 2002)   Node-Centric Hybrid R...
Pending publications
Simulation Results (10 flows)Total Control Bytes   Total MAC layer packets
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Final

  1. 1. Dissertation DefenseOn-Demand Link-State Routing in Ad-Hoc Networks Soumya Roy Computer Engineering, University Of California, Santa Cruz Adviser : Prof. JJ Garcia Luna Aceves
  2. 2. Presentation Outline Wireless ad-hoc networks On-demand link-state routing protocol  Source-tree On-demand Adaptive Routing protocol (SOAR)  Path Selection  On-demand Link Vector Protocol (OLIVE) Node-centric hybrid routing approach for practical scenarios of ad-hoc networks
  3. 3. PART ONE Wireless Ad Hoc Networks
  4. 4. Wireless Ad Hoc Networks WLAN Ad hoc NetworksNodes acts as sources, relays and destinations of data packets Routing protocol is needed for data delivery
  5. 5. Challenges in Designing Routing Protocols for Mobile Ad-Hoc Networks Significant Packet Loss :  Fading, interference, collisions Less bandwidth than wired networks Network Topology highly dynamic because of router or host mobility Routing protocols should adapt fast to link failures and converge fast Routing overhead should be minimal
  6. 6. Taxonomy of Routing Protocols Proactive Routing (WRP, DSDV, OLSR, STAR)  Maintains routes for all destinations  Redundant routes Reactive Routing (AODV, DSR, DST)  Maintains routes for necessary nodes  Uses flooding of requests to discover paths  Long delays for path set up
  7. 7. Main goal is to ….Explore how link-state information can be used efficiently for setting up on-demand routes
  8. 8. Previous Work Proactive link-state protocols  Source Tree Adaptive Routing (STAR)  Exchanges source trees  Topology Broadcast based on Reverse-Path Forwarding (TBRPF)  Exchanges reportable part of source tree  Optimized Link-State Routing (OLSR)  Uses multipoint relays to prevent flooding Performance good compared to on-demand routing protocols using routing information in other forms
  9. 9. PART TWO On-Demand Link- State Routing
  10. 10. Outline Source Tree On-demand Adaptive Routing (SOAR) Challenges in the path selection On-demand Link Vector Routing (OLIVE)
  11. 11. Source Tree On-demand Adaptive Routing (SOAR)
  12. 12. What is Source Tree Each node can build source tree based on paths to all reachable destinations a b c SOAR exchanges minimal source trees d e f g h i j k l m Source Tree at node a
  13. 13. What is a Minimal Source Tree Contains paths to important nodes (relays, potential relays, receivers) a a b b c c d e f d e f jj g jjg h i k Minimal Source Tree l m l reported by node a Source Tree at a
  14. 14. Construction of Topology Table i x a a x i y c i c y + =Minimal source tree Minimal source tree Partial topology at i of x of a  Modified Bellman-Ford Algorithm used for path selection
  15. 15. Summary Query, Reply for path discovery Updates for path repair ForcedUpdate, ForcedReply for forcing nodes adopt shortest paths Links validated using sequence number Data packets contain traversed paths
  16. 16. Performance Evaluation (ns2) 20 nodes 1000mx300m rectangular field IEEE 802.11 MAC Link layer notification of link failures Re-routing of data packets possible in case of link breakage Comparisons with DSR and AODV
  17. 17. Effect of Increasing Flows (pause=0s)
  18. 18. Effect of Mobility (10 flows)
  19. 19. Effect of Loading (10 flows)
  20. 20. Challenges of Path Selection in On-demand Link State Routing
  21. 21. Path Selection Algorithm Links advertised by b (c) (c) c d f Links advertised by c (c) (c) (c) a (b) (c) g (b) h (b) e b Path through a neighbor valid if later has advertised it Choose the shortest among the valid options
  22. 22. Computing Source TreeOPT-TREE : Given a graph and a set oflabels corresponding to each link, whatis maximum size of the source tree thatcan be built while satisfying the rules ofshortest path and on-demand routeadvertisement?NP complete problem (reduction of3SAT problem to a graph)
  23. 23. Computing Source Tree (contd…)
  24. 24. Heuristic for Computing Source Tree A polynomial time approximation (O(nd^2)) algorithm Finding shortest valid paths for a destination and combining those paths Local maxima instead of global maxima Disadvantage: computing source tree not an efficient usage of routing information A mechanism for policy-based routing
  25. 25. Computing source graph (in SOAR) MBF BF (a,d1) (x,d2) j d1 >d2 (x,d2) i i i k (a,d1+1)(x,inf) (x, d2+1) a x a x a xd1 d2 j (j,k) link has been j j advertised by x only k k kPartial topology at i Source Graph at i Advertised Source Tree at i
  26. 26. How does SOAR handle pathselection problem Computes source graph Exchanges source trees Uses forced routing to convert source graphs to trees Disadvantage:  Loops can form  Extra overhead of forced routing
  27. 27. Next Step ……. Use of complete path information Links in paths validated using sequence numbers Links merged to help in local route repair and limited route requests Instantaneous loops to be prevented without any control overhead in data packets or any global synchronization
  28. 28. On-Demand Link Vector Protocol(OLIVE)
  29. 29. Overview of OLIVE Route discovery  Setting up new paths  RREQ, RREP and RREPACK Route Repair  Locally repair routes or limit route searches  FRREQ, FRREP Route Failure Notification  To notify route failures  RERR, RERRACK
  30. 30. Use of path information in OLIVE
  31. 31. Use of path information (contd …) c e
  32. 32. RREQ d a RR EQRREQi j k RR EQ c b RREQ RREPACK RREP a d RR EP RREP Example (Route Discovery)i j k RR RREPACK PE RR AC b K c EP RREP RREPACK
  33. 33. Example (Route Error and Repair) j j d c d c RREQ FRREQ RREQ FRREP a b a b FR EQ RR FR RE RERRACK RR EQ RE P k RERR k Q i RREQ i
  34. 34. Properties of OLIVE When cost of path can increase, inter- neighbor synchronization is used  Predecessors release the successor  Loop-free paths set up when all predecessors release Every node knows correctly at every instance its set of predecessors Data packets from unknown predecessors always dropped
  35. 35. Performance Evaluation (ns2) 50 nodes 1500x300m (range = 250m) 2Mbps DSSS radio interface Random Waypoint model IEEE 802.11 Compared with DSR, OLSR, TBRPF, AODV
  36. 36. Simulation Results (10 flows)Percentage Throughput Total Control Packets
  37. 37. Simulation Results (10 flows)Optimality of routes End to end delay
  38. 38. Effect of Packet Load (20 sources)Control packets sent Percentage Delivery
  39. 39. Effect of Packet Load (20 sources)Optimality of routes End-to-end Delay
  40. 40. Quantifying loopsPacket rate = 8 packets/s Packet rate = 10 packets/s
  41. 41. Summary Elaborately studied the problem of using on-demand link-state information for routing Developed routing solutions that give better performance than existing popular routing protocols OLIVE can be very good choice for use in ad hoc networks
  42. 42. PART 2Node-Centric Hybrid Routing for Ad Hoc Networks
  43. 43. Outline Introduction Reasons behind node-centric hybrid routing Methods and new protocols Performance evaluation
  44. 44. Introduction Practical scenarios for mobile ad-hoc networks will have traffic between mobile nodes and netmarks Where can we see such scenarios :  Internet Access Points  Hosts for DNS services  Web Proxies  Group leaders  Cluster-heads for hierarchical routing
  45. 45. Practical Ad Hoc Networks
  46. 46. Related Work in Hybrid Routing Zone Routing Protocol (Haas & Pearlman)  Proactive routing within zones  Reactive routing between zones Landmark Hierarchy (P.F. Tshuchiya)  Node centric approach to hierarchical routing for proactive routing  Landmark’s address: address for common node Our approach: Type of routing is based on nodes and not on zones or areas
  47. 47. Why Node-centric Hybrid Routing On Demand path creation towards netmarks  Each session set up leads to flooding, delay  Intuitively not best approach if the netmark is communicated frequently though not continuously Maintaining pro-active routes  High control overhead  Redundant paths as peer-to-peer communication is much less compared to number of nodes Node-centric hybrid routing: a tradeoff  Proactive routes towards netmarks  On demand path creation among mobile nodes
  48. 48. Methods of Node-Centric HybridRouting  Prolonged Caching  Caching of netmark information for long enough periods  Proactive routes  Proactive routing for the netmark so that paths towards netmarks remain always updated while paths between mobile nodes are set up on-demand
  49. 49. Protocols with Prolonged Caching Route errors and route requests for netmarks do not depend on traffic AODV : longer routing entry timeout for netmarks DSR : advantage not realizable since routing solely controlled by traffic SOAR :Netmarks will be important for longer time interval, hence caches/maintains netmark path information for longer periods
  50. 50. Protocols With Proactive Netmark Routes1. Nemarks advertise their presence  MAC layer sends beacons  Routing Layer sends Hellos2. Route errors and route requests for netmarks do not depend on traffic Changes 1 and 2 can be easily made for DSR, SOAR and AODV
  51. 51. Protocols with Proactive Routes(contd…)3. New paths to netmarks are always advertised Change 3 needs modifications  SOAR sends updates immediately on discovering new routes  AODV and DSR need new type of control packets for proactive route set up
  52. 52. SOAR with Hybrid Functionality SOAR performs better than both DSR or AODV Modifications of SOAR to incorporate hybrid routing simpler than in DSR or AODV Netmark Aware On Demand Link-State Routing (NOLR) : extended caching of netmarks Netmark-Enhanced Source Tree Routing (NEST) : proactive routes for netmarks
  53. 53. Setting up paths in NEST  Forward paths are set up proactively Reverse paths are set up by traffic flows (soft state or on-demand) (e,b) hel (e,a) lo n n lo nhel b b b (e,d) update a a (e,c) a (e,c) update dupd (e,e) d d (e,e) at e c c c update e e e
  54. 54. Issues in Hybrid Routing Forwarding of data packets  Use of subnet address for ad hoc networks Multiple Netmarks  Load balancing  Complexity in packet forwarding (static, dynamic, hybrid affiliations)  Asymmetry in paths  Change in query mechanism (anycast queries)
  55. 55. Performance Evaluation Using ns2 Comparison of NEST, NOLR with DSR, AODV and SOAR
  56. 56. Traffic and Mobility Models Mobility Model : random waypoint model Traffic Pattern  FLOW OFF/ON model  Data Traffic and Voice traffic Simulation
  57. 57. Simulation Scenario 1 31 nodes single netmark in the centre of a rectangular field (1000m x 500m) size Range = 250m Simulation length : 600 secs load = 3 packets/sec 5 packets/sec Speed : 5m/s-20m/s
  58. 58. Performance Evaluation (3 pkts/s) Percentage ThroughputControl packet
  59. 59. Performance Evaluation (5 pkts/s)Control packets Percentage Throughput
  60. 60. Simulation Scenario 2 31 nodes single netmark  Static  Mobile in a restricted region  Mobile throughout the rectangular field Traffic flows ( 2 models)  6 random flows among netmark and mobile nodes (battlefield or relief)  Any mobile node can talk to netmark (Internet)
  61. 61. Performance Evaluation
  62. 62. Simulation Scenario 3 31 nodes Two static netmarks To observe : can anycast route discovery lead to any significant improvement
  63. 63. NEST A-SOAR NOLRPerformance Evaluation
  64. 64. Contributions First detailed study on use of link-state information on-demand Developed two unique highly efficient routing protocols Demonstrated the complexity of path selection in on-demand routing Presented a new genre of hybrid routing targeting practical ad-hoc networks
  65. 65. Future Work Opportunistic version of OLIVE to target practical ad-hoc networks Node-centric version targeting huge networks without added complexity of hierarchy management Modeling ad-hoc networks based on parameters like node density
  66. 66. Acknowledgements Thanks to JJ for being the greatest adviser Thanks to Richard, Katia for being on my defense committee, and Suresh for being on my advancement committee. Thanks to my parents and brother who have always supported me Thanks to my friends in Baskin Engineering, Bay Area and CCRG for all the help during my PhD life
  67. 67. THE END
  68. 68. Publications SOAR (IEEE Infocom 2001) Heuristic for Source Tree Computation (ICCCN 2002) Node-Centric Hybrid Routing (Globecom 2002, Mascots 2002, Book Chapter) Path Selection problem (submitted to PODC 2003) OLIVE (Mobicom 2003)
  69. 69. Pending publications
  70. 70. Simulation Results (10 flows)Total Control Bytes Total MAC layer packets

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