Redes Inalámbricas – Tema 3. Mobile Ad Hoc Networks

1. Redes Inalámbricas – Tema 3. Mobile Ad Hoc Networks Specific properties Flooding as a basic mechanism Basic routing protocols DSR AODV y DYMO OLSR y OLSRv2 Advanced protocols and techniques • Acknowledgments : • Nitin H. Vaidya, “Tutorial on Mobile Ad Hoc Networks: Routing, MAC and Transport Issues” • Available at: http://www.crhc.uiuc.edu/wireless/tutorials.html

2. Redes Inalámbricas – Tema 3. Mobile Ad Hoc Networks Specific properties Flooding as a basic mechanism Basic routing protocols DSR AODV y DYMO OLSR y OLSRv2 Advanced protocols and techniques • Acknowledgments : • Nitin H. Vaidya, “Tutorial on Mobile Ad Hoc Networks: Routing, MAC and Transport Issues” • Available at: http://www.crhc.uiuc.edu/wireless/tutorials.html

3. Wireless ad hoc network

4. Unit disk graph 1

5. Unit disk graph

6. Routing Overview • Goal: transfer message from one node to another • Which is the “best” path? Generally try to optimize one of the following: • Shortest path (fewest hops) • Shortest time (lowest latency) • Shortest weighted path (utilize available bandwidth, battery) • Who decides - source or intermediate nodes? • Source (“path”) routing [Like airline travel] • Source specifies entire route • Intermediate nodes just forward to specified next hop • Destination (“hop-by-hop”) routing [Like postal service] • Source specifies only destination in message header • Intermediate nodes look at destination in header, consult internal tables to determine appropriate next hop

7. MANET Routing Properties • Distributed operation • No external network setup  “self-configuring” • Efficient when network topology is dynamic (frequent network changes – links break, nodes come and go) • And also: • Loop Freedom • Sleep period operation • Unidirectional link support • Security • Quantitative Properties • End-to-End data throughput • Delays • Route Acquisition time • Out of order delivery (percentage)

8. Types of protocols behaviour • Proactive protocols • They determine routes independently from the traffic patterns • Traditional protocols like link-state and distance-vector are proactive • Reactive protocols • They create a route only if required • There are also hybrid solutions • Aspects to take into consideration • Waiting time for getting a route • Proactive protocols are typically faster • Reactive protocols normally have a higher latency • Overhead for route discover and maintenance • Proactive protocols typically have an higher overhead because they are always updating routing tables • Reactive protocols normally have a lower overhead because they add control traffic only when necessary The solution to adopt depends on the type of the data traffic and the type of mobility!

9. manet Working Group • IETF WG: Mobile Ad-hoc Networks (manet) • http://www.ietf.org/html.charters/manet-charter.html • Additional MANET links:http://www.ianchak.com/manet/ • Additional information is available at: http://tools.ietf.org/wg/manet • Purpose of MANET working group • standardize IP routingprotocol functionality suitable for wireless routing application within both static and dynamic topologies with increased dynamics due to nodemotion or other factors. • Approaches are intended to be: • relatively lightweight in nature • suitablefor multiple hardware and wireless environments, and address scenarios • MANETs are deployed at the edges of an IP infrastructure • hybridmesh infrastructures (e.g., a mixture of fixed and mobile routers)should also be supported by MANET specifications and management features.

10. manet Working Group • The group is pursuing a reactive and a proactive protocol. On the charter page these are called RMP and PMP respectively. • Proactive MANET Protocol (PMP) • Reactive MANET Protocol (RMP) • In practice the reactive protocol is DYMO and the proactive is OLSRv2. • If significant commonality between RMP and PMP modules is observed, the WG may decide to go with a converged approach. • Both IPv4 and IPv6 will be supported. • Routing security requirements and issues will also be addressed. • The MANET WG will also develop a scoped forwarding protocol that can efficiently flood data packets to all participating MANET nodes.

11. Proposedprotocols • Here: http://en.wikipedia.org/wiki/Ad_hoc_protocol_list

12. Classification of Ad Hoc Routing Protocols Routing protocols for ad hoc wireless networks Based on routing information update mechanism Based on topology information Proactive(table-driven or link-state) Reactive(table-driven) Hybrid Flat routing Hierarchical routing • ZRP • HSR • DSDV • OLSR • HSR • DSR • AODV • DYMO • DSDV • DSR • AODV • DYMO Based on the use of temporal information for routing Based on utilization of specific resources Path selection using past history Path selection using prediction Energy-aware routing Geographical routing • PAR • GPSR • FORP • DSDV • DSR • AODV • DYMO

13. Mostrelevantroutingprotocols • D. Johnson, D. Maltz, and Y-C. Hu. The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks (DSR),RFC 4728, February 2007. http://tools.ietf.org/html/rfc4728 • C. Perkins, E. Belding-Royer, and S. Das. Ad hoc On-Demand Distance Vector (AODV) Routing. RFC 3561, July 2003. http://tools.ietf.org/html/rfc3561 • I. Chakeres, C. Perkins. Dynamic MANET On-demand (DYMO) Routing.draft-ietf-manet-dymo-17, March 2009. http://tools.ietf.org/html/draft-ietf-manet-dymo-17 • T. Clausen et al. The Optimized Link-State Routing Protocol version 2. draft-ietf-manet-olsrv2-08, March 2009. • T. Clausen and P. Jacquet. Optimized Link State Routing Protocol (OLSR). RFC 3626, October 2003. http://www.ietf.org/rfc/rfc3626.txt

14. Redes Inalámbricas – Tema 3. Mobile Ad Hoc Networks Specific properties Flooding as a basic mechanism Basic routing protocols DSR AODV y DYMO OLSR y OLSRv2 Advanced protocols and techniques • Acknowledgments : • Nitin H. Vaidya, “Tutorial on Mobile Ad Hoc Networks: Routing, MAC and Transport Issues” • Available at: http://www.crhc.uiuc.edu/wireless/tutorials.html

15. Node that just forwarded a frame Node that just received a frame Frame broadcasted Flooding as a basic mechanism 1/6 Y Z S L E B M F C J D A G K H N I destination

16. Node that just forwarded a frame Node that just received a frame Frame broadcasted Flooding as a basic mechanism 2/6 Y Z S L E F B M C J A G D H K N I possible collision!!

17. Node that just forwarded a frame Node that just received a frame Frame broadcasted Flooding as a basic mechanism 3/6 Y Z S L E F B M J C A G D H K N I Receives the frame but does not forward it. Already done

18. Node that just forwarded a frame Node that just received a frame Frame broadcasted Flooding as a basic mechanism 4/6 Y Z S L E M F B J C A G D H K N I Receives the frame form J and from K (which are mutually hidden)  possible collision

19. Node that just forwarded a frame Node that just received a frame Frame broadcasted Flooding as a basic mechanism 5/6 Y Z S L E M F B J C A G D H K N I D does not forward it because is the final destination

20. Node that just forwarded a frame Node that just received a frame Frame broadcasted Flooding as a basic mechanism 6/6 Y Z S L E M F B J C A G D H K N I Floodingisover!

21. Flooding as a basic mechanism: a few considerations • Many protocols use limited flooding of the control packets. • Control packets are used to discover the routes. • Advantage: Simplicity • Disadvantage: Overhead possibly very high • The established routes are then used to send packets of data.

22. Redes Inalámbricas – Tema 3. Mobile Ad Hoc Networks Specific properties Flooding as a basic mechanism Basic routing protocols DSR AODV y DYMO OLSR y OLSRv2 Advanced protocols and techniques • Acknowledgments : • Nitin H. Vaidya, “Tutorial on Mobile Ad Hoc Networks: Routing, MAC and Transport Issues” • Available at: http://www.crhc.uiuc.edu/wireless/tutorials.html

23. Dynamic Source Routing (DSR) • Fornetworks of mediumsize (200 nodes), admitshighspeeds • When node S wants to send a packet to node D, but does not have a route to D, begins a routediscoveryprocess. • Sourcenode S floodsRouteRequest (RREQ) packets • Eachnodeaddsitsown id whenit forwards a RREQ. • Use of the “send buffer”

24. Node that just forwarded an RREQ Node that just received a RREQ [X,Y] IDs list added to the RREQ Route Request in DSR, 1/5 Y S [S] E B M F C J D A G K H N I destination

25. Node that just forwarded an RREQ Node that just received a RREQ [X,Y] IDs list added to the RREQ Route Request in DSR, 2/5 Y Z E [S,E] S L F B M C [S,C] J A G D H K N I Possible collision!!

26. Node that just forwarded an RREQ Node that just received a RREQ [X,Y] IDs list added to the RREQ Route Request in DSR, 3/5 Y Z S L E F [S,E,F] B M J C A G [S,C,G] D H K N I RREQ is not forwarded

27. Node that just forwarded an RREQ Node that just received a RREQ [X,Y] IDs list added to the RREQ Route Request in DSR, 4/5 Y Z S L E M F B J [S,E,F,J] C A G D K[S,C,G,K] H N I Possible collision

28. Node that just forwarded an RREQ Node that just received a RREQ [X,Y] IDs list added to the RREQ Route Request in DSR, 5/5 Y Z L S E M [S,E,F,J,M] F B J C A G D H K N I

29. Z S RREP [S,E,F,J,D] L E M F B J C A G D H K N I RouteReply Y • Destination D, when receiving the first RREQ send a Route Reply (RREP) • RREP is sent using the route obtained by reversing the one that is in the received RREQ

30. Route Reply en DSR • Route Reply can be sent by reversing the route in Route Request (RREQ) only if links are guaranteed to be bi-directional • To ensure this, RREQ should be forwarded only if it received on a link that is known to be bi-directional • If unidirectional (asymmetric) links are allowed, then RREP may need a route discovery for S from node D • Unless node D already knows a route to node S • If a route discovery is initiated by D for a route to S, then the Route Reply is piggybacked on the Route Request from D. • If IEEE 802.11 MAC is used to send data, then links have to be bi-directional (since Ack is used)

31. Dynamic Source Routing (DSR) • Node S on receiving RREP, caches the route included in the RREP • When node S sends a data packet to D, the entire route is included in the packet header • hence the name source routing • Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded

32. Data Delivery in DSR Packet header size grows with route length Y Z DATA [S,E,F,J,D] S L E M F B J C A G D H K N I

33. Y Z L E S M F B J C D A K H G N I DSR Optimization: Route Caching (1/2) • 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 packets

34. Y Z L E S M F B J C D A K H G N I DSR Optimization: RouteCaching (2/2) • When node S learns that a route to node D is broken, it uses another route from its local cache, if such a route to D exists in its cache. Otherwise, node S initiates route discovery by sending a route request • Node X on receiving a Route Request for some node D can send a Route Reply if node X knows a route to node D • Use of route cache • can speed up route discovery • can reduce propagation of route requests

35. Y Z S L RERR [J-D] E M F B J C A G D H K N I Route Error (RERR) • J sends a route error to S along route J-F-E-S when its attempt to forward the data packet S (with route SEFJD) on J-D fails • Nodes hearing RERR update their route cache to remove link J-D • Each node is responsible for confirming that the link can be used to transmit data. • Ack del MAC (p.ej., 802.11) • Passive acks • DSR-specific ACK

36. DSR additionaltechniques • “Expading ring” technique playing with the TTL of the packets • “non propagating” Route Request • “Route salvaging” technique for route maintenance • Dynamic substitution of routes for intermediate ndoes • “Automatic route shortening” technique for routes optimization • Based on “gratuitous” Route Reply • The “flows”

37. DSR: advantages and disadvantages • Routes maintained only between nodes who need to communicate • reduces overhead of route maintenance • Route caching can further reduce route discovery overhead • A single route discovery may yield many routes to the destination, due to intermediate nodes replying from local caches • Packet header size grows with route length due to source routing • Flood of route requests may potentially reach all nodes in the network • Care must be taken to avoid collisions between route requests propagated by neighboring nodes • insertion of random delays before forwarding RREQ • Increased contention if too many route replies come back due to nodes replying using their local cache • Route Reply Storm problem • Reply storm may be eased by preventing a node from sending RREP if it hears another RREP with a shorter route

38. Redes Inalámbricas – Tema 3. Mobile Ad Hoc Networks Specific properties Flooding as a basic mechanism Basic routing protocols DSR AODV y DYMO OLSR y OLSRv2 Advanced protocols and techniques • Acknowledgments : • Nitin H. Vaidya, “Tutorial on Mobile Ad Hoc Networks: Routing, MAC and Transport Issues” • Available at: http://www.crhc.uiuc.edu/wireless/tutorials.html

39. First Back to basics : Distance Vector protocol • Basic Routing Protocol • known also as Distributed Bellman-Ford or RIP • Every node maintains a routing table • all available destinations • the next node to reach the destination • the number of hops to reach the destination • Periodically send table to all neighbors to maintain topology • Bi-directional links are required! Thanks to Raoul Reuter

40. First Back to basics : Distance Vector -> tables 1 2 A B C Thanks to Raoul Reuter

41. First Back to basics : Distance Vector -> update B broadcasts the new routing information to his neighbors Routing table is updated (A, 1) (B, 0) (C, 1) (A, 1) (B, 0) (C, 1) A change occurs so… 1 21 A B C Thanks to Raoul Reuter

42. First Back to basics : Distance Vector -> new node broadcasts to update tables of C, B, A with new entry for D (A, 1) (B, 0) (C, 1) (D, 2) (A, 2) (B, 1) (C, 0) (D, 1) (D, 0) 1 1 1 A B C D Thanks to Raoul Reuter

43. First Back to basics : Distance Vector • Broken Link and consequent Loops… 1 1 1 D A B C (D, 2) (D, 2) 1 1 1 D A B C Thanks to Raoul Reuter

44. First Back to basics : Distance Vector • … create the “Count to Infinity” problem (D,5) (D,4) (D,4) (D,3) (D,2) (D,2) 1 1 1 D A B C Thanks to Raoul Reuter

45. Ad Hoc On-DemandDistance Vector Routing (AODV) • DSR includes source routes in packet headers. • Resulting large headers can sometimes degrade performance • particularly when data contents of a packet are small • AODV attempts to improve on DSR by maintaining routing tables at the nodes, so that data packets do not have to contain routes • AODV retains the desirable feature of DSR that routes are maintained only between nodes which need to communicate

46. AODV • Route Requests (RREQ) are forwarded in a manner similar to DSR • When a node re-broadcasts a Route Request, it sets up a reverse path pointing towards the source • AODV assumes symmetric (bi-directional) links • When the intended destination receives a Route Request, it replies by sending a Route Reply • Route Reply travels along the reverse path set-up when Route Request is forwarded

47. Node that just forwarded a frame Node that just received a frame RREQ broadcast Route Request in AODV Y Z S L E B M F C J D A G K H N I destination

48. Node that just forwarded a frame Node that just received a frame RREQ broadcast Inverse link Route Request in AODV Y Z S L E F B M C J A G D H K N I

49. Node that just forwarded a frame Node that just received a frame RREQ broadcast Inverse link Route Request in AODV Y Z S L E F B M J C A G D H K N I

50. Node that just forwarded a frame Node that just received a frame RREQ broadcast Inverse link Route Request in AODV Y Z S L E M F B J C A G D H K N I