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Lecture 11 14. Adhoc routing protocols cont..


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Lecture 11 14. Adhoc routing protocols cont..

  1. 1. Lecture (11-14) --- On-Demand-Driven Reactive Routing protocols Chandra Prakash Assistant Professor LPU
  2. 2. Ad Hoc Routing Protocol  Routing protocols category : (a)Table-driven, (b) Source-initiated on-demand-driven. 2
  3. 3. 3 Overview of Current Routing Protocols
  4. 4. 4 Table-driven vs. On-demand  Table-Driven Routing Protocol:  proactive  continuously evaluate the routes  attempt to maintain consistent, up-to-date routing information  when a route is needed, one may be ready immediately  when the network topology changes  the protocol responds by propagating updates throughout the network to maintain a consistent view
  5. 5. 5 Table-driven vs. On-demand (cont.)  Source-Initiated On-Demand Routing Protocol:  Reactive  on-demand style: create routes only when it is desired by the source node  route discovery: invoke a route-determination procedure, the procedure is terminated when  a route has been found  no route is found after all route permutations are examined  route maintained by a route maintenance procedure until  inaccessible along every path from the source  no longer desired  longer delay: sometimes a route may not be ready for use immediately when data packets come
  6. 6. On-Demand Driven/ Reactive protocols In a reactive protocol, a route is discovered only when it is necessary. In other words, the protocol tries to discover a route only on- demand, when it is necessary. These protocols generate much less control traffic at the cost of latency, but it usually takes more time to find a route compared to a proactive protocol. 6
  7. 7. Source-Initiated On-Demand Approaches  Creates routes only when desired by the source node.  finds a route on demand by flooding the network with Route Request packets.  When a node requires a route to a destination, it initiates a route discovery process within the network.  Completed when either a route is found or all possible route permutations have been examined.  Once a route has been discovered and established, it is maintained by some form of route maintenance procedure until either the destination becomes inaccessible along every path from the source or the route is no longer desired. 7
  8. 8. 8 Source-initiated on-demand 1. Dynamic Source Routing (DSR)  D. B. Johnson and D.A. Maltz,“Dynamic Source Routing inAd-HocWireless Networks,” Mobile Computing,T. Imielinski and H. Korth, Eds., Kluwer, 1996, pp. 153–81. 2. Ad-Hoc on-demand distance vector routing (AODV)  C. E. Perkins and E. M. Royer,“Ad-hoc On-Demand DistanceVector Routing,” Proc. 2nd IEEEWksp. Mobile Comp. Sys. andApps., Feb. 1999, pp. 90–100. 3. Temporally ordered routing algorithm (TORA)  V. D. Park and M. S. Corson,“A HighlyAdaptive Distributed RoutingAlgorithm for MobileWireless Networks,” Proc. INFOCOM ’97,Apr. 1997. 4. Associativity-Based routing (ABR)  C-K.Toh,“A Novel Distributed Routing ProtocolTo SupportAd-Hoc Mobile Computing,” Proc. 1996 IEEE 15thAnnual Int’l. Phoenix Conf. Comp. and Commun., Mar. 1996, pp. 480–86. 5. Signal stability routing (SSR)  R. Dube et al.,“Signal Stability basedAdaptive Routing (SSA) forAd-Hoc Mobile Networks,” IEEE Pers. Commun., Feb. 1997, pp. 36–45.
  9. 9. 1. Dynamic Source Routing (DSR) D. B. Johnson and D.A. Maltz,“Dynamic Source Routing inAd-HocWireless Networks,” Mobile Computing,T. Imielinski and H. Korth, Eds., Kluwer, 1996, pp. 153–81.  On-demand routing protocol  based on the concept of source routing  Designed to restrict the bandwidth consumed by control packets in table driven approach  Eliminated the periodic table-update message (hello packet/ beacon) 9
  10. 10. Dynamic Source Routing (DSR)  Each host maintains a route cache which contains all routes it has learnt.  Source Routing:  routes are denoted with complete information (each hop is registered)  Two major parts:  route discovery  route maintenance 10
  11. 11. Dynamic Source Routing (DSR)  When a host has a packet to send, it first consults its route cache.  If there is an unexpired route, then it will use it.  Otherwise, a route discovery will be performed Route Discovery:  Initiates by broadcasting a route request packet.  Source node S floods Route Request (RREQ)  Route request message contains  Address of the destination,  Source node's address and  Unique identification number.  Each node appends own identifier(Sequence number) when forwarding RREQ Entries in the route cache are continually updated as new routes are learned. 11
  12. 12. Dynamic Source Routing (DSR)  There is a “route record” field in the packet.  The source node will add its address to the record.  On receipt of the packet, a host will add its address to the “route record” and rebroadcast the packet.  Each node receiving the packet checks whether it knows of a route to the destination.  If it does not, it adds its own address to the route record of the packet and then forwards the packet along its outgoing links.  To limit the number of ROUTE_REQUEST packets:  Each node only rebroadcasts the packet at most once.  Each node will consult its route cache to see if a route is already known. 12
  13. 13. Route Discovery in DSR 13 B A S E F H J D C G I K Z Y Represents a node that has received RREQ for D from S M N L
  14. 14. Route Discovery in DSR B A S E F H J D C G I K Represents transmission of RREQ Z Y Broadcast transmission M N L [S] [X,Y] Represents list of identifiers appended to RREQ14
  15. 15. Route Discovery in DSR B A S E F H J D C G I K • Node H receives packet RREQ from two neighbors: potential for collision Z Y M N L [S,E] [S,C] 15
  16. 16. Route Discovery in DSR B A S E F H J D C G I K • Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once Z Y M N L [S,C,G] [S,E,F] 16
  17. 17. Route Discovery in DSR 17 B A S E F H J D C G I K Z Y M • Nodes J and K both broadcast RREQ to node D • Since nodes J and K are hidden from each other, their transmissions may collide N L [S,C,G,K] [S,E,F,J]
  18. 18. Route Discovery in DSR 18 B A S E F H J D C G I K Z Y • Node D does not forward RREQ, because node D is the intended target of the route discovery M N L [S,E,F,J,M]
  19. 19. Route Discovery in DSR  A ROUTE_REPLY packet is generated when  the route request packet reaches the destination  an intermediate host has an unexpired route to the destination  Destination D on receiving the first RREQ, sends a Route Reply (RREP)  RREP is sent on a route obtained by reversing the route appended to received RREQ  RREP includes the route from S to D on which RREQ was received by node D 19
  20. 20. Route Reply in DSR 20 B A S E F H J D C G I K Z Y M N L RREP [S,E,F,J,D] Represents RREP control message
  21. 21. Dynamic Source Routing  The ROUTE_REPLY packet will contain a route generated in following manner:  Use the route of destination route cache (if route cache has the route information)  the route that was traversed by the ROUTE_REQUEST packet (if symmetric)  route discovery and piggyback the route reply on the new request (if asymmetric)  Node S on receiving RREP, caches the route included in the RREP  Source routing  When node S sends a data packet to D, the entire route is included in the packet header  Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded21
  22. 22. Data Delivery in DSR 22 B A S E F H J D C G I K Z Y M N L DATA [S,E,F,J,D] Packet header size grows with route length
  23. 23. 23 Dynamic Source Routing (DSR) Routing discovery routing reply
  24. 24. 24 Dynamic Source Routing (DSR)  Routing maintenance  Use acknowledgements or a layer-2 scheme to detect broken links.  Inform sender via route error packet.  Initiate route discovery.  All routes which contain the breakage hop have to be removed from the route cache. Route Error packet
  25. 25. destination source 1 6 5 4 3 2 8 7 (1,4) (1,2) (1,3) (1,3,5,6)(1,3,5) (1,4,7) source broadcasts a packet containing address of source and destination The route looks up its route caches to look for a route to destination If not find, appends its address into the packet The destination sends a reply packet to source. The node discards the packets having been seen 25
  26. 26. DSR Overview Advantages  Designed to restrict the bandwidth consumed by control packets in table driven approach  Eliminated the periodic table-update message (hello packet/ beacon)  Routes maintained only between nodes who need to communicate (on demand )thus 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 Disadvantage  Packet header size grows with route length due to source routing degrade performance- when data contents of a packet are small  Flood of route requests may potentially reach all nodes in the network  Potential collisions between route requests propagated by neighboring nodes  Increased contention if too many route replies come back due to nodes replying using their local cache  Route Reply Storm problem 26
  27. 27. 2. Ad Hoc On-Demand Distance Vector Routing Protocol (AODV) C. E. Perkins and E. M. Royer,“Ad-hoc On-Demand DistanceVector Routing,” Proc. 2nd IEEE Wksp. Mobile Comp. Sys. andApps., Feb. 1999, pp. 90–100.  DSR includes source routes in packet headers, resulting large headers.  AODV attempts to improve on DSR  by maintaining routing tables at the nodes, so that data packets do not have to contain routes,  InAODV, the source node and the intermediate nodes store the next hop information corresponding to each flow data packet transmission.  AODV relies on dynamically establishing route table entries at intermediate node.  AODV retains the desirable feature of DSR that routes are maintained only between nodes which need to communicate 27
  28. 28. Ad Hoc On-Demand Distance Vector Routing Protocol  AODV is an improvement on DSDV  minimizes the number of required broadcasts  by creating routes on an on-demand basis  AODV use the concept of destination sequence number from DSDV to determine an up-to-date path to the destination.  It is a pure on-demand route acquisition system  AODV only supports the use of symmetric links.  Nodes which are not on a selected path do not maintain routing information or participate in routing table exchanges. 28
  29. 29. 29 AODV  Includes  Route discovery  Route maintenance.  Path discovery procedure using RREQ/RREP query cycles.  Reverse Path setup  Forward path setup  Route table management  AODV maintains routes as long as they are active.  Path maintenance  The source moves: reinitiate the route discovery  Other node moves: a special RREP is sent to the affected source nodes  Local connectivity management  Broadcasts used to update local connectivity information  Inactive nodes in an active path required to send “hello” messages
  30. 30. Route Requests in AODV 30 B A S E F H J D C G I K Z Y Represents a node that has received RREQ for D from S M N L
  31. 31. AODV  Route Requests (RREQ) are forwarded in a manner similar to DSR  Route request message contains  Source identifier (SrcID)  Destination identifier (DestID)  Source sequence number (SrcSeqNum)  Destination sequence number (DestSeqNum)  Broadcast identifier (BcastID) andTime to live(TTL) field  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 (RREP)  Route Reply travels along the reverse path set-up when Route Request is forwarded31
  32. 32. Route Requests in AODV 32 B A S E F H J D C G I K Represents transmission of RREQ Z Y Broadcast transmission M N L
  33. 33. Route Requests in AODV 33 B A S E F H J D C G I K Represents links on Reverse Path Z Y M N L
  34. 34. Reverse Path Setup in AODV 34 B A S E F H J D C G I K • Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once Z Y M N L
  35. 35. Reverse Path Setup in AODV 35 B A S E F H J D C G I K Z Y M N L
  36. 36. Reverse Path Setup in AODV 36 B A S E F H J D C G I K Z Y • Node D does not forward RREQ, because node D is the intended target of the RREQ M N L
  37. 37. Forward Path Setup in AODV 37 B A S E F H J D C G I K Z Y M N L Forward links are setup when RREP travels along the reverse path Represents a link on the forward path
  38. 38. Ad Hoc On-Demand Distance Vector Routing (AODV)  AODV uses destination sequence numbers to ensure that all routes are loop-free and contain the most recent route information.  Each node maintains its own sequence number, as well as a broadcast ID.  The broadcast ID is incremented for every RREQ the node initiates, and together with the node's IP address, uniquely identifies an RREQ.  Source node includes in the RREQ the most recent sequence number it has for the destination.  Intermediate nodes can reply to the RREQ only if they have a route to the destination whose corresponding destination sequence number is greater than or equal to that contained in the RREQ. 38
  39. 39. Ad Hoc On-Demand Distance Vector Routing (AODV)  At the time of forwarding the RREQ, intermediate nodes record the address of neighbors from which the first copy of broadcast packet was received, in their route tables, to establishing a reverse path.  Once the RREQ has reached the destination,  It responds by unicasting a route reply (RREP) packet back to the neighbor from which it first received the RREQ and so on.  As the RREP is routed back along the reverse path, nodes along this path set up forward route entries in their route tables that point to the node from which the RREP came.  A route timer is associated with each route entry, which causes the deletion of the entry if it is not used within a specified lifetime.  Because an RREP is forwarded along the path established by an RREQ, AODV only supports the use of symmetric links. 39
  40. 40. Route Request and Route Reply  Route Request (RREQ) includes the last known sequence number for the destination  An intermediate node may also send a Route Reply (RREP) provided that it knows a more recent path than the one previously known to sender  Intermediate nodes that forward the RREP, also record the next hop to destination  A routing table entry maintaining a reverse path is purged after a timeout interval  A routing table entry maintaining a forward path is purged if not used for a active_route_timeout interval 40
  41. 41. Ad Hoc On-Demand Distance Vector Routing (AODV)  Consideration for other better routes is absent in AODV.  This approached was first proposed in Associativity Based Routing (ABR) in 1994 and protected by the ABR US patent.  In AODV, routes are maintained as follows:  If a source node moves, it reinitiate the route discovery protocol to find a new route.  If a node along the route moves, its upstream neighbor notices the move and propagates a link failure notification message (an RREP with an infinite metric) to each of its active upstream neighbors to inform them of the erasure of that part of the route.  These nodes in turn propagate the link failure notification to their upstream neighbors, and so on, until the source node is reached.  The source node may then choose to re-initiate route discovery for that destination if a route is still desired.41
  42. 42. AODV: Summary Advantages  The authors claim scalability up to 10,000 nodes (performance suffers, simulation results)  Routes are established on demand  Routes need not be included in packet headers  Nodes maintain routing tables containing entries only for routes that are in active use  Destination sequence no are used to find the latest route to the destination  Sequence numbers are used to avoid old/broken routes and formation of routing loops  Connection setup is less Disadvantage  Intermediate nodes can lead to inconsistent routes if the source sequence no is very old and the intermediate node have a higher but not the latest destination sequenced no.  Periodic beaconing leads to unnecessary bandwidth consumption. 42
  43. 43. 3. Temporally Ordered Routing Algorithm (TORA) V. D. Park and M. S. Corson,“A HighlyAdaptive Distributed RoutingAlgorithm for Mobile Wireless Networks,” Proc. INFOCOM ’97,Apr. 1997.  TORA is proposed to operate in a highly dynamic mobile networking environment.  Highly adaptive, loop-free, distributed routing algorithm based on the concept of link reversal.  Key design concept ofTORA  localization of control messages to a very small set of nodes near the occurrence of a topological change.  To accomplish this, nodes need to maintain routing information about adjacent (one- hop) nodes.  The height metric is used to model the routing state of the network.  The protocol performs three basic functions:  (a) route creation, (b) route maintenance, and (c) route erasure. 43
  44. 44. 44 TORA: Temporally ordered routing  During the route creation and maintenance phase, nodes establish a directed acyclic graph(DAG).  A logical direction is imposed on the links towards the destination  Source-initiated and provides multiple routes for any desired source/destination pair.  Starting from any node in the graph, a destination can be reached by following the directed links  Highly adaptive, efficient, scalable, distributed algorithm  Multiple routes from source to destination  For highly dynamic mobile, multi-hop wireless network A C E D F G B
  45. 45. 45 TORA  Assigns a reference level (height) to each node  A DAG is maintained for each destination  Synchronized clock is important, accomplished via GPS or algorithm such as NetworkTime Protocol.  Timing is an important factor forTORA because the “height” metric is dependent on the logical time of a link failure.  metric:  logical time of a link failure  The unique ID of the node that defined the new reference level  A reflection indicator bit  A propagation ordering parameter  The unique ID of the node  Adjust reference level to restore routes on link failure  Query,Update,Clear packets used for creating, maintaining and erasing routes
  46. 46. 46 TORA  Three major tasks  Route creation: QRY and UPD packets  Route maintenance  Route erasure: Clear packet (CLR) is broadcasted  Using Unique node ID and unique reference ID  Route Creation: demand driven “query/reply”  Performed only when a node requires a path to a destination but does not have nay directed link.  A query packet (QRY) is flooded through network  An update packet (UPD) propagates back if routes exist  Route Maintenance: “link-reversal” algorithm  React only when necessary  Reaction to link failure is localized in scope  Route Erasure:  A clear packet (CLR) is flooded through network to erase invalid routes
  47. 47. 47 TORA  Route creation of TORA 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 s s d d Propogation of QRY (reference level, height) Height of each node updated by UPD Route Creation in TORA (-,-) (-,-) (-,-) (-,-) (-,-) (-,-) (0,0) (-,-) (0,3) (0,3) (0,3) (0,2) (0,1) (0,0) (0,1)(0,2)
  48. 48. 48 TORA  Creation of route C A B E G (DEST) F H D QRY QRY QRY UPD QRY QRY UPD UPD UP D UPD UPD UPD
  49. 49. a f e d c b h g (-,-,-,-,d) (-,-,-,-,b) (-,-,-,-,c) (-,-,-,-,f)(-,,-,-,-e) Only the non-NULL node (destination) responds with a UPD packet. (0,0,0,0,h) (-,-,-,-,a) The source broadcasts a QRY packet with height(D)=0, all others NULL (0,0,0,4,b) (0,0,0,4,c) (0,0,0,3,e) (0,0,0,2,f) (0,0,0,2,d) (0,0,0,3,a) source Dest. A node receiving a UPD sets its height to one more than UPD Source receives a UPD with less height UPD QRY QRYQRY (-,-,-,-,g)(0,0,0,1,g) 49 QRY QRY QRY QRY QRY QRY
  50. 50. 50 TORA  Route maintenance C A B E G (DEST) F H D UPD X UPD UPD
  51. 51. 51 TORA
  52. 52. TORA: Summary Advantages  Less control overload: by limiting the control packets for route reconfiguration to a small region Disadvantage  The local reconfiguration of paths results in non-optimal routes  Concurrent deduction of partitions and subsequent deletion of routes could result in temporary oscillations and transient loops. 52
  53. 53. 4. ABR: Associativity-Based routing C-K.Toh,“A Novel Distributed Routing ProtocolTo SupportAd-Hoc Mobile Computing,” Proc. 1996 IEEE 15thAnnual Int’l. Phoenix Conf. Comp. and Commun., Mar. 1996, pp. 480–86.  First routing protocol that advocates the selection of stable links and routes for ad hoc wireless networks.  Goal: Best route is selected based on stability and shortest path of wireless link .  Associativity is related to the spatial, temporal, and connection stability of a mobile host (MH).  The stability is measured using associativity ticks(initially set to zero)  Each node broadcasts beacons, the nodes increment associativity ticks when they receive beacons and sets zero if beacon is not received. High Associativity means high stability.  A node's association with its neighbors changes as it is migrating, and its transition period can be identified by associativity ticks or counts. 53
  54. 54. Associativity-Based routing  Selects route based on the stability for the wireless links.  Beacon-based, on demand routing protocol  Link is classified as stable or unstable based on its temporal stability  Temporal stability is determined by counting the periodic beacons that a node receive from its neighbors.  Each node maintains the count of its neighbors’ beacons and on the basis of beacon count corresponding to the neighbor node concerned. classifies each link as  stable link : link corresponding to a stable neighbor  unstable : link to an unstable neighbor  A source node floods RouteRequest packets in the network if a route is not available in its route cache.  All intermediate node forward the RouteRequest packets. 54
  55. 55. Associativity-Based routing  RouteRequest packet carries the path it has traversed and the beacon count for the corresponding nodes in the path.  When the first RouteRequest reaches the destination , the destination waits for a period TrouteselceteTime to receive multiple RouteRequest through different paths.  After this time , destination selects the path that has the max. no of stable links.  If two paths have same proportion of stable links, shortest path is selected.  If more than one shortest path available, random path is selected.  ABR doesn't restrict any intermediate node from forwarding a RouteRequest packet based on the stable or unstable link criterion.  It uses stability information only during the route selection process at the destination node.  ABR give more priority to stable routes than to shorter routes. 55
  56. 56. 56 Associativity-Based routing  Source Initiated Routing, Query-Reply packets  Route is long-lived and free from loops, deadlock, and packet duplicates  ABR provides the method of reconstructing when link fails  The protocol contains 3 phases:  Route discovery: BQ-REPLY cycle  Route reconstruction (RRC):  Route deletion (RD): Source-initiated
  57. 57. 57 ABR  Route discovery: accomplished by a broadcast query and await-reply(BQ- REPLY) cycle.  A node desiring a route broadcasts a BQ message . In search of mobiles a route broadcasts a BQ(Broadcast query) message in search of mobiles that have a route to the destination  All nodes receiving the BQ append their address and their associativity ticks with their neighbors along with QoS information to query packet.  A successor node erases its upstream node neighbor’s associativity ticks entries and retains only the entry concerned with itself and its upstream node.  The destination computes the total of the associativity ticks  The destination will know all the possible routes and their qualities. It then selects the best route based on stability and associativity ticks.  If multiple paths have the same overall degree of association stability, the route with minimum number of hops is selected.
  58. 58. Temporal and spatial representation of associativity of a mobile node with its neighbors. 58
  59. 59. Rule and Property of Associativity 59  Scenario:  cell size d = 10m  MH min migration speed v = 2m/s  Beacon transmission interval p = 1s  Athreshold = 2 r /(vp) = 5 Association stability results when no. of beacons recorded is > Athreshold  Low associativity ticks  high state of mobility  High associativity ticks  stable state Stability is also determined by signal strength and power life.
  60. 60. ABR  Stability in ABR refers to more than just associativity ticks. It also includes  signal strength:defines the quality of the signal propagation channel  power life:describes the current power life of the device  Advances in radio transceiver technology has enabled one to monitor signal strength over time and store this information into memory.  Advances in smart battery technology has enabled us to monitor remaining power life of battery-powered devices.  Such information, can be used to govern route stability. 60
  61. 61. ABR: Summary Advantages  Stable routes have a higher preference compared to shorter routes.  Fewer path breaks  Reduce the extent of flooding due to reconfiguration of paths in the network. Disadvantage  Chosen Path maybe longer than the shortest path between the source and destination because of the preference given to stable paths.  Local query (LQ) broadcast may result in high delays during route repairs . 61
  62. 62. 62 5. Signal Stability Routing (SSR)  Advance form of ABR  New metric: signal strength between nodes and a node’s location stability  Selects routes based on signal strength between nodes Prefers stronger connectivity.  Tables  Signal Strength Table (SST)–  Periodic beacons from the link layer of the neighbouring nodes:  fields [host, signal strength, last, clicks, set]  Signal strength recorded by SST-- Weak or Strong  Routing Table (RT)  field [destination, next host].  Two protocols  Dynamic Routing Protocol (DRP): manages SST & RT  Static Routing Protocol (SRP): forwards packets based on RT
  63. 63. 63 SSR (cont.)
  64. 64. Signal Stability Routing (SSR) SSR consists of 2 cooperative protocols:  Dynamic Routing (DRP)  Maintain signal stability table(SST) with and routing table(RT)  After updating all appropriate table entries, the DRP passes a received packet to the SRP  Static Routing (SRP) :  Passing the packet up the stack if it is the intended receiver  If no entry is found in the RT for the destination, initiate a route-search process to find a route  Else forwarding the packet  Send a route reply message back to initiator  All transmission are received and processed by DRP  After processing and updating the table DRP passes the packets to SRP 64
  65. 65. 65 SSR (cont.)  Route discovery and route maintenance  By default, only route request packets from strong channels are forwarded  initiate a new route-search process; erase the old route  If there is no route-reply message received, the route changes to accept weak channel. A B C D E F A B C D E F
  66. 66. SSR ( route search)  Passes the packets to the stack or look for destination in RT  If no entry is in RT for destination a new route search process is initiated.  Weak channels are accepted only if timed out occur for receiving a route reply message.  In case of link failure intermediate nodes send error message to the source indicating the broken channel and a new route search process is initialized  Assumptions:  Route search packets arrives at destination along the strongest signal capability 66
  67. 67. S D Weak link route search route reply 67
  68. 68. SSR: Summary Advantages  To select strong connection leads to fewer route reconstruction  More stable route as compared to shortest path route selection protocols such as AODV and DSR. Disadvantage  Long delay since intermediate nodes can’t answer the path (unlikeAODV, DSR) 68
  69. 69. 6. Location-Aided Routing (LAR) 69
  70. 70.  Exploits location information to limit scope of flooding for route request  Limit the search for a new route to a smaller request zone.  Reduce the signalling traffic  Location information may be obtained using GPS  Two concept:  Expected zone  Request zone  Assumption:  Sender has advanced knowledge about location and velocity of the destination 6. Location-Aided Routing (LAR) 70
  71. 71. Location-Aided Routing (LAR)  Expected zone:  determined as a region that is expected to hold the current location of the destination node (D)  Determination is based on potentially old location information, and knowledge of the destination’s speed  Request Zone :  Smallest rectangle that include the location of sender and expected zone.  The sender explicitly defines the request zone ( co-ordinates of the rectangular request zone)  The nodes can discard a route request packet if it is not under the request zone.  Route requests limited to a Request Zone that contains the Expected Zone and location of the sender node (S)71
  72. 72. Location-Aided Routing (LAR)  Expected Zone in LAR  Request Zone in LAR 72
  73. 73. Operation of LAR  Only nodes within the request zone forward route requests  NodeA does not forward RREQ, but node B does  Request zone explicitly specified in the route request  Each node must know its physical location to determine whether it is within the request zone  If route discovery using the smaller request zone fails to find a route,the sender initiates another route discovery (after a timeout) using a larger request zone  the larger request zone may be the entire network Rest of route discovery protocol similar to DSR 73
  74. 74. Operation of LAR  When Destination node (D) receives the route request message, it replies by sending a route reply message (as in the flooding algorithm).  Node D includes its current location and current time in the route reply message.  When node S receives this route reply message (ending its route discovery), it records the location of node D.  Node S can use this information to determine the request zone for a future route discovery. 74
  75. 75. LAR: Summary Advantages  Limit the search for a new route to a smaller request zone.  Reduces the scope of route request flood  Reduce the signaling traffic  Reduces overhead of route discovery Disadvantage  Nodes need to know their physical locations  GPS is needed for pre-knowledge of the location of the destination  Positional error may affect routing  Does not take into account possible existence of obstructions for radio transmissions75
  76. 76. 7. Power –Aware Routing (PAR) 76
  77. 77. Why POWER concerns ?  The lifetime of a network is defined as the time it takes for a fixed percentage of the nodes in a network to die out.  Portability of wireless nodes being critical its almost mandatory to keep the battery sizes to a bare necessary.  Since battery capacity is fixed, a wireless mobile node is extremely energy constrained  Hence all network related transactions should be power aware to be able to make efficient use of the overall energy resources of the network 77
  78. 78. Metrics ( objectives) Battery life is taken as routing metric 1. Minimize energy consumed / packet 2. Maximize time to Network Partition 3. Minimize variance in node power levels 4. Minimize cost / packet 5. Minimize maximum node cost 78
  79. 79. Power-Aware Routing 79
  80. 80. 8. Zone Routing Protocol (ZRP) 80
  81. 81. Hybrid protocol of reactive and proactive approach Disadvantage of reactive: reactive protocols have higher latency in discovering routes. Disadvantage of proactive: proactive protocols generate a high volume of control messages required for updating local routing tables. ZRP: The proactive part of the protocol is restricted to a small neighbourhood of a node and the reactive part is used for routing across the network. This reduces latency in route discovery and reduces the number of control messages as well. 81
  82. 82. 82 ZRP: Zone routing protocol  Hybrid of table-driven and on-demand!!  From each node, there is a concept of “zone”.  Within each zone, the routing is performed in a table-driven manner (proactive), similar to DSDV.  However, a node does not try to keep global routing information.  For inter-zone routing, on-demand routing is used.  This is similar to DSR.
  83. 83. Zone routing protocol  A routing zone :  Comprises a few mobile ad hoc nodes within one, two, or more hops away from where the central node is formed.  Zones can overlap.  Each node specifies a zone radius in terms of radio hops.  Similar to a cluster with the exception that every node acts as a cluster head and a member of other clusters.  Within this zone, a table-driven-based routing protocol is used.  Each node, therefore, has a route to all other nodes within the zone.  If the destination node resides outside the source zone, an on- demand search-query routing method is used. 83
  84. 84. Zone routing protocol 84
  85. 85. ZRP  ZRP has three sub-protocols:  the proactive (table-driven) Intrazone Routing Protocol (IARP),  the reactive Interzone Routing Protocol (IERP), and  the Bordercast Resolution Protocol (BRP). a) Intrazone Routing Protocol (IARP)  the proactive (table-driven) approach  IARP can be implemented using existing link-state or distance-vector routing.  ZRP's IARP relies on an underlying neighbor discovery protocol to detect the presence and absence of neighboring nodes  Ensure that each node within the zone has a consistent routing table to reflect up-to-date information 85
  86. 86. ZRP b) Reactive Interzone Routing Protocol (IERP), and  Relies on border nodes to perform on-demand routing to search for routing information to nodes residing outside its current zone.  IERP uses the bordercast resolution protocol. c) the Bordercast Resolution Protocol (BRP).  Instead of allowing the query broadcast to penetrate into nodes within other zones, the border nodes in other zones that receive this message will not propagate it further.  Relies on border nodes to perform on-demand routing to search for routing information to nodes residing outside its current zone.  Without proper query control, ZRP can actually perform worse than standard flooding-based protocols 86
  87. 87. ZRP  ZRP's route discovery process is, route table lookup and/or interzone route query search.  When a route is broken due to node mobility,  if the source of the mobility is within the zone  it will be treated like a link change event and an event-driven route updates used in proactive routing will inform all other nodes in the zone.  If the source of mobility is a result of the border node or other zone nodes,  then route repair in the form of a route query search is performed, or in the worst case, the source node is informed of route failure. 87
  88. 88. 9. SourceTree Adaptive Routing (STAR) 88
  89. 89. Proactive routing protocol Does not need routing updates Does not attempts to maintain optimum path Examines updating strategies used table driven routing approaches like ORA Each node maintains a source tree Source tree is the set of links used by an ad hoc host in its preferred path to destination Aggregation is done on host adjacent links and the source trees of the neighbours. Aggregation creates a partial topology graph Each node runs route selection algorithm on its own source node tree to derive a routing table which can specifies the successor to each destination Uses sequence numbers to validate link state updates (LSU) A host accepts a LSU if the sequence number is higher than the previous or there is no entry till. Only changes to the validity of the tree are propagated. Dijkstra’s shortest path algorithm is used to select routes. 89
  90. 90. 10. Reactive Distance Microdiversity Routing (RDMAR) 90
  91. 91.  Estimates the distance between two nodes using the relative distance estimation algorithm in radio hops.  It is a source initiated routing protocol  It limits the range of route searching in order to save the cost of flooding a route request message into the entire wireless area.  It is assumed in RDMAR that all ad hoc mobile hosts are migrating at the same fixed speed.  Route Discovery  Transmission of route discovery packets  If a current relative estimate is present then search flood is limited to this distance  Destination node returns reply message over reverse path.  Reply message moves backward while intermediate nodes establish the forward route hop-by-hop 91
  92. 92. Route maintenance  The node that notifies a link breakage invokes localized route discovery to find partial path to destination.  If link breakage location is closer to the sender then the route failure message is sent to the source.  The intermediate nodes which have the routing information regarding this linkage , must have to remove their entries from the routing tables.  It is assumed that all links are bidirectional  It uses the shortest route as the routing metric. 92
  93. 93. 93 Summary On-demand AODV DSR TORA ABR SSA Overall complexity Medium Medium High High High Overhead Low Medium Medium High High Routing philosophy Flat Flat Flat Flat Flat Loop-free Yes Yes Yes Yes Yes Multicast capability Yes No No No No Beaconing requirements No No No Yes yes Multiple route support No Yes Yes No No Routes maintained in Route table Route cache Route table Route table Route table Route reconfiguration methodlogy Erase route; notify source Erase route; notify source Link reversal; route repair Localized broadcast query Erase route; notify source Routing metric Freshest and shortest path Shortest path Shortest path Associativity and shortest path and others Associati vity and widest Comparisons of the characteristics of source-initiated on demand routing protocol
  94. 94. 94 Overview Parameters On Demand Table Driven Availability of Routing Information Available when needed Always available regardless of need Routing Philosophy Flat Mostly Flat except for CGSR Periodic route updates Not Required Yes Coping with Mobility Using Localized route discovery in ABR Inform other nodes to achieve consistent routing tables SignalingTraffic Generated Grows with increasing mobility of active nodes as in ABR Greater than that of On Demand Routing QoS Support Few Can Support QoS Mainly Shortest Path as QoS Metric
  95. 95. Reference 1. Routing Protocols for Ad Hoc Mobile Wireless Networt by Padmini Misra, 99/adhoc_routing/index.html#CBRP 2. A Comparison of On-Demand and Table Driven Routing for Ad-Hoc Wireless Networks, by Jyoti Raju and J.J. Garcia-Luna-Aceves, 3. A New Routing Protocol for the Reconfigurable Wireless Networks, Zygmunt J Hass 4. Caching strategies in on-demand routing protocols for wireless ad hoc networks, by Yih-chun hu and Divid B. Johnson, 5. Highly Dynamic Destination-Sequenced Distance-Vector Routing for Mobile Computers, Pravin Bhagwat, Charles E. Perkins 6. Dynamic source routing in ad hoc wireless networks, by David B. Johnson and David A. Maltz, 7. A Performace Comparison of Multi-Hop Wireless Ad Hoc Network Routing Protocols, Josh Broch etc 8. An Efficient Routing Protocol for Wireless Netwrok, Shree Murthy etc 9. Temporally-Ordered Routing Algorithm (TORA) Version 1 Funtional Specification, by V. Park, S. Corson, collection/corson-draft-ietf-manet-tora-spec-00.txt 10. Ad Hoc On Demand Distance Vector (AODV) Routing, by Charles Perkins, 00.txt95
  96. 96. Reference (cont.) 7. An Introduction to Mobile Ad Hoc Network, by MingYu Jiang, 8. Scalable Routing Strategies for Ad hocWireless Network, by Atsushi Iwata , Ching- Chuan Chiang etc. 9. A Performance Comparison of Multi-HopWireless Ad Hoc Network Routing Protocols, by Josh Broch, David A. Maltz, David B. Johnson,Yih-Chun Hu, Jorjeta Jetcheva, performance-comparison-mobicom98.pdf 10. Fisheye State Routing:A Routing Schema for Ad HocWireless Networks, by guangyu Pei, Mario Gerla,Tsi-Wei Chen 11. A review of current Routing protocols for ad-hoc MobileWireless Networks, by Elizabeth M. Royer and C-KToh 12. CEDAR: a Core-Extraction distributed Ad Hoc Routing Algorithm, Prasun Sinha, Vaduvur Nharghavan, etc 13. Mobile computing today & in the future, by M.J. Fahham and M.K. Hauge. 14. Performance Comparison of On-demand Routing Protocols in Ad Hoc Network by Sohela Kaniz wireless/projects_spring2000/pres_kaniz.pdf 96