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Dynamic source routing


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Dynamic source routing

  1. 1. DSR: The Dynamic Source RoutingProtocol for Multi-Hop Wireless Ad HocNetworks Presenter Ashraf Uddin Sujit Singh South Asian University (Master of Computer Applications)
  2. 2. Routing Overview Network with nodes, edges Goal: Devise scheme for transferring message from one msg node to another  Destination routing  Source routing
  3. 3. Source (“path”) routing Source specifies entire route: places complete path to destination in message header: A – D – F – G Intermediate nodes just forward to specified next hop: D would look at path in header, forward to F Like airline travel – get complete set of tickets to final destination before departing…
  4. 4. Destination (“hop-by-hop”) routing Source specifies only destination in message header: G Intermediate nodes look at destination in header, consult internal tables to determine appropriate next hop Like postal service – specify only the final destination on an envelope, and intermediate post offices select where to forward next…
  5. 5. Ad Hoc Routing Every node participates in routing: no distinction between “routers” and “end nodes” No external network setup: “self-configuring” Especially useful when network topology is dynamic (frequent network changes – links break, nodes come and go)
  6. 6. Common application Mobile wireless hosts  Only subset within range at given time  Want to communicate with any other node
  7. 7. DSR Protocol Activities Route discovery  Undertaken when source needs a route to a destination Route maintenance  Used when link breaks, rendering specified path unusable
  8. 8. Route Discovery• The source sends a broadcast packet which contains source address, destination address, request id and path.• If a host saw the packet before, discards it.• Otherwise, the route looks up its route caches to look for a route to destination, If not find, appends its address into the packet, rebroadcast,• If finds a route in its route cache, sends a route reply packet, which is sent to the source by route cache or the route discovery.
  9. 9. source broadcasts a packet containing address of source anddestination source (1,4) 1 4 The destination sends a reply packet to source. 8 (1,3) destination 3 7 (1,4,7) 2 The node discards the packets having been seen (1,2) 6 5 (1,3,5) (1,3,5,6) The route looks up its route caches to look for a route to destination If not find, appends its address into the packet
  10. 10. How to send a reply packet If the destination has a route to the source in its route cache, use it Else if symmetric links are supported, use the reverse of route record Else if symmetric links are not supported, the destination initiates route discovery to source
  11. 11. Route Maintenance Whenever a node transmits a data packet, a route reply, or a route error, it must verify that the next hop correctly receives the packet. If not, the node must send a route error to the node responsible for generating this route header  Intermediate nodes “eavesdrop”, adjust cached routes Source deletes route; tries another if one cached, or The source restart the route discovery
  12. 12. Route Maintenance……A B C D E Route error message: C-D is broken
  13. 13. DSR Optimization: Route Caching Each node caches a new route it learns by any means When node S finds route [S,E,F,J,D] to node D, node S also learns route [S,E,F] to node F When node K receives Route Request [S,C,G] destined for node, node K learns route [K,G,C,S] to node S When node F forwards Route Reply RREP [S,E,F,J,D], node F learns route [F,J,D] to node D When node E forwards Data [S,E,F,J,D] it learns route [E,F,J,D] to node D A node may also learn a route when it overhears Data
  14. 14. Additional Route Discovery features DSR route discovery does not allow nodes like F to reply to RREQ
  15. 15. Additional Route Discovery features
  16. 16. Additional Route Discovery features
  17. 17. Additional Route Discovery features Node C may infer Preventing Route Reply that the initiator has already received a h=2 storms Route Reply giving  Many Route Reply message C a better route could be send to A from the because the data A’s neighbors packet received  To avoid a possible local from B contains a congestion, each nodes must value of “h” less wait a variable period before than its h’s value A B G sending the reply.  Delay period d = H(h - 1 + r) h=1  Each node network interfaces works into “promiscuous” E receive mode. h=3
  18. 18. Additional Route Discovery features Route request Hop limits  “Nonpropagating” Route Request(hop lim 0)  To determine if the target is 2 Hop limit neighbour or a neighbour has a route 1 Hop limit to the target cached.  “Propagating” Route Request( no hop lim) Non Propagating  If no route reply is recived after a Route Request The expanding ring search approach can carry to the short timeout. average latency increasing  “Expanding ring”  Increase hop value stepwise if no route reply is recieved.
  19. 19. Additional Route Maintenance features
  20. 20. Additional Route Maintenance features
  21. 21. Additional Route Maintenance features
  22. 22. Additional Route Maintenance features
  23. 23. Support for Heterogeneous networks & mobile IP Heteregenous network : Different kind of devices with different interfaces. Possibly , multiple interfaces( short range & long range)
  24. 24. DSR evaluation Simulation  To analyse the behavior and performance of DSR.  To Compare with other routing protocols Set Up:  Ad hoc of 50 mobiles nodes  15 minutes ( 900 seconds) simulation time.  CBR data traffic  20 mobile nodes traffic sources; 4 packets/sec.  Random waypoint mobility model ( pause time)
  25. 25. Packet Delivery Ratio(with movement speed 1m/s)
  26. 26. Routing Overhead(with movement speed 1m/s)
  27. 27. Packet Delivery Ratio(with movement speed 20m/s)
  28. 28. Routing Overhead(with movement speed 20m/s)
  29. 29. RESULT At both movement speeds, DSR delivers almost all data packets, regardless of pause time. 100% delivery ratio at pause time 900 sec, a stationary network. At 1 m/s delivery ratio> 99.5% At 20 m/s delivery ratio> 98%
  30. 30. Advantages Routes maintain only between nodes who need to communicate. Reduces overhead of routing maintenance. route caching reduces route discovery overhead. A single route may yield many routes to the destination.
  31. 31. Disadvantages Packet header size grows with route length due to source routing. Flood route request may potentially reach all nodes in the network. Route reply storm problem.
  32. 32. Conclusion Excellent performance for routing in multi-hop ad hoc. Very low routing overhead. Able to deliver almost all originated data packets, even with rapid motion of all nodes.
  33. 33. THANKS
  34. 34. Reference[1]. David B. Johnson, David A. Maltz, and Josh Broch, "DSR: The Dynamic Source Routing Protocol for Multi-Hop Wireless Ad Hoc Networks", in Ad Hoc Networking, edited by Charles E. Perkins, Chapter 5, pp. 139-172, Addison- Wesley, 2001. Invited paper.
  35. 35. ?????? QUESTION??????