Redes Inalámbricas Tema 4. Mobile Ad Hoc Networks

Redes Inalámbricas Tema 4. Mobile Ad Hoc Networks A. Specific properties B. Flooding as a basic mechanism C. Basic routing protocols DSR AODV y DYMO OLSR y OLSRv2 D. 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 Máster de Ingeniería de Computadores 2008/2009

3 Network with nodes, edges Goal: transfer message from one node to another Which is the best path? Who decides - source or intermediate nodes? Routing Overview msg

4 Which 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 determines route? 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 Routing Overview Intermediate nodes look at destination in header, consult internal tables to determine appropriate next hop

5 No external network setup: self-configuring MANET Routing Properties Efficient when network topology is dynamic (frequent network changes links break, nodes come and go) Self Starting Adapt to network conditions Qualitative Properties Distributed operation Loop Freedom Demand Based Operation Security Sleep period operation Unidirectional link support Quantitative Properties End-to-End data throughput Delays Route Acquisition time Out of order delivery (percentage) Efficiency

6 Host mobility Why is Routing in MANET different? link failure/repair due to mobility may have different characteristics than those due to other causes Rate of link failure/repair may be high when nodes move fast New performance criteria are used route stability despite mobility energy consumption host position Dynamic Solution much more difficult to be deployed

7 Proactive protocols Types of protocols behaviour 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!

8 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 manet Working Group Purpose of MANET working group standardize IP routing protocol functionality suitable for wireless routing application within both static and dynamic topologies with increased dynamics due to node motion or other factors. Approaches are intended to be: relatively lightweight in nature suitable for multiple hardware and wireless environments, and address scenarios MANETs are deployed at the edges of an IP infrastructure hybrid mesh infrastructures (e.g., a mixture of fixed and mobile routers) should also be supported by MANET specifications and management features.

9 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.

Work in progress perspective 10

11 Here: http://en.wikipedia.org/wiki/ad_hoc_protocol_list Proposed protocols

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

14 Node that just forwarded a frame Flooding as a basic mechanism 1/2 Y Node that just received a frame Frame broadcasted Z B S E F M L C J A G D H I K possible collision!! N

15 Node that just forwarded a frame Flooding as a basic mechanism 1/3 Y Node that just received a frame Frame broadcasted Z B S E F J M L C A G D H K I N Receives the frame but does not forward it. Already done

16 Node that just forwarded a frame Flooding as a basic mechanism 1/4 Y Node that just received a frame Frame broadcasted Z B S E F J M L C A G D H K I Receives the frame form J and from K (which are mutually hidden) possible collision N

17 Node that just forwarded a frame Flooding as a basic mechanism 1/5 Y Node that just received a frame Frame broadcasted Z B S E F J M L C A G D H K I D does not forward it because is the final destination N

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

19 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. The established routes are then used to send packets of data. Advantage: simplicity Disadvantage: Overhead possibly very high

20 Most relevant routing protocols 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

22 Dynamic Source Routing (DSR) For networks of medium size (200 nodes), admits high speeds When node S wants to send a packet to node D, but does not have a route to D, begins a route discovery process. Source node S floods Route Request (RREQ) packets Each node adds its own id when it forwards a RREQ. Use of the send buffer

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

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

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

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

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

28 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 Route Reply Z Y S E RREP [S,E,F,J,D] M L B F J C A G D H I K N

29 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 bidirectional (since Ack is used)

30 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

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

32 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 A B H S C I E G F J K Z D M Y N L

33 DSR Optimization: Route Caching (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 Y A B H S C I E G F J K Z D M N L

34 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 Route Error (RERR) Nodes hearing RERR update their route cache to remove link J-D Y 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 B S C E Z RERR [J-D] F J M L A H I G K D N

35 DSR additional techniques 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

36 Routes maintained only between nodes who need to communicate reduces overhead of route maintenance DSR: advantages and disadvantages Packet header size grows with route length due to source routing Flood of route requests may potentially reach all nodes in the network 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 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 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 to 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

39 First Back to basics : Distance Vector -> tables A 1 2 B C Dest. Next Metric Dest. Next Metric Dest. Next Metric A A 0 B B 1 C B 3 A A 1 B B 0 C C 2 A B 3 B B 2 C C 0 Thanks to Raoul Reuter

40 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 A 1 2 1 B C Dest. Next Metric Dest. Next Metric Dest. Next Metric A A 0 B B 1 C B 3 2 A A 1 B B 0 C C 1 A B 3 2 B B 1 C C 0 Thanks to Raoul Reuter

41 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) A 1 1 B C 1 D Dest. Next Metric Dest. Next Metric Dest. Next Metric A A 0 A A 1 A B 2 B B 1 C B 2 D B 3 B B 0 C C 1 D C 2 B B 1 C C 0 D D 1 Thanks to Raoul Reuter

42 Broken Link and consequent Loops First Back to basics : Distance Vector A 1 1 B C 1 D Dest. Next Metric Dest.c Next Metric Dest. Next Metric D B 3 D C 2 D DB 1 (D, 2) (D, 2) A 1 1 B C 1 D Dest. Next Metric D B 3 Dest. Next Metric D C 2 Dest. Next Metric D B 3 Thanks to Raoul Reuter

43 create the Count to Infinity problem First Back to basics : Distance Vector (D,5) (D,4) (D,4) (D,3) (D,2) (D,2) A 1 1 B C 1 D Dest. Next Metric D B 3, 5, Dest.c Next Metric D C 2, 4, 6 Dest. Next Metric D B 3, 5, Thanks to Raoul Reuter

44 Ad Hoc On-Demand Distance 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

45 Route Requests (RREQ) are forwarded in a manner similar to DSR AODV 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

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

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

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

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

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

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

52 Forward links are setup when RREP travels along the reverse path Forward Path Setup in AODV Z Y B S E F J M L C A G D H K I N

53 AODV table entries AODV uses the following fields with each route table entry: Destination IP Address Destination Sequence Number Valid Destination Sequence Number flag Other state and routing flags (e.g., valid, invalid, repairable, being repaired) Network Interface Hop Count (number of hops needed to reach destination) Next Hop List of Precursors Lifetime (expiration or deletion time of the route)

54 Details about the route reply Route Reply in AODV An intermediate node (not the destination) may also send a Route Reply (RREP) provided that it knows a more recent path than the one previously known to sender S To determine whether the path known to an intermediate node is more recent, destination sequence numbers are used If Node:dsn >= RREQ:dsn do not forward The likelihood that an intermediate node will send a Route Reply when using AODV not as high as DSR A new Route Request by node S for a destination is assigned a higher destination sequence number. An intermediate node which knows a route, but with a smaller sequence number, cannot send Route Reply Timeouts A routing table entry maintaining a reverse path is purged after a timeout interval timeout should be long enough to allow RREP to come back A routing table entry maintaining a forward path is purged if not used for a active_route_timeout interval if no data is being sent using a particular routing table entry, that entry will be deleted from the routing table (even if the route may actually still be valid)

55 Notificación sobre interrupción de enlaces A neighbor of node X is considered active for a routing table entry if the neighbor sent a packet within active_route_timeout interval which was forwarded using that entry When the next hop link in a routing table entry breaks, all active neighbors are informed Link failures are propagated by means of Route Error messages, which also update destination sequence numbers When node X is unable to forward packet P (from node S to node D) on link (X,Y), it generates a RERR message Node X increments the destination sequence number for D cached at node X The incremented sequence number N is included in the RERR When node S receives the RERR, it initiates a new route discovery for D using destination sequence number at least as large as N

56 Link Failure Detection Hello messages: Neighboring nodes periodically exchange hello message Absence of hello message is used as an indication of link failure Alternatively, failure to receive several MAC-level acknowledgement may be used as an indication of link failure

57 DYMO DYMO Reactive Protocol like AODV, but with path accumulation feature S I1 I2 I3 D 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type Len TTL I A Res +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+. TargetAddress. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ TargetSeqNum +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ THopCnt Res 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G RBPrefix Res RBHopCnt +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+. RBNodeAddress. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ RBNodeSeqNum +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ NL +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ RREQ RREP RREQ RE-S RREQ RE-S RE-I1 RREQ RE-S RE-I1 RE-I2 RE-S Route Element with NL of S RE-I1 Route Element with NL of I1 RREQ RE-S RE-I1 RE-I2 RE-I3

58 Avoid expiring good routes Update reverse route lifetime on data reception Update forward route lifetime on data transmission Inform sources of broken routes quickly Active links must be monitored Several mechanisms available Route Error (RERR) Optional additional invalid routes DYMO Route Maintenance

59 DYMO vs AODV Answers by Ian Chakeres to the question: could you briefly explain what are the differences between DYMO and AODV 8 Mar 2005 There are several differences between AODV, AODV-bis, DSR and DYMO. To list just a few. 23 Mar 2006 New packet format. Generic packet handling. Unsupported element handling. Optional path accumulation. Much more. DYMO is a simpler version of AODV. DYMO is easier to implement and has lower requirements (in terms of memory, code, etc.) than AODV. DYMO is close to what has been implemented for sensor networks, such as tinyaodv. AODV is no longer being explored in the MANET WG.

61 Optimized Link State Routing (OLSR) Proactive scheme based on the link-state mechanism. Each node periodically floods status of its links Each node re-broadcasts link state information received from its neighbor Each node keeps track of link state information received from other nodes Each node uses above information to determine next hop to each destination The overhead of flooding link state information is reduced by requiring fewer nodes to forward the information Does not require modifying the structure of the IP packets

62 OLSR v2 Compared to OLSRv1, OLSRv2 retains the same basic mechanisms and algorithms, while providing an even more flexible signaling framework and some simplification of the messages being exchanged. OLSRv2 takes care to accommodate both IPv4 and IPv6 addresses in a compact fashion. The message exchange format has been factored out to an independent specification Clausen, T., Dean, J., Dearlove, C., and C. Adjih, "Generalized MANET Packet/Message Format", work in progress. The OLSRv2 neighborhood discovery protocol using HELLO messages has been factored out to an independent specification Clausen, T., Dean, J., and C. Dearlove, "MANET Neighborhood Discovery Protocol (NHDP)", work in progress.

63 The overload of broadcasting the status information on the links is reduced by limiting the number of nodes which forward this information A broadcast from node X is forwarded only by its multipoint relays The multipoint relays of X are its neighbors chosen so that every twohops neighbors of X is a one-hop neighbors of at least one of its multipoint relay Each node periodically transmits the list of its neighbors so that all nodes can know which are their two-hops neighbors, therefore being able to choose their multipoint relays 24 broadcasts are needed to spread the message up to three hops away 11 broadcasts are needed to spread the message up to three hops away LSR vs. OLSR Sending node Sending node

64 Nodes can have various OLSR interfaces, each with its own IP address Each node is assigned a unique reference IP ( main address ) neighbor: x is a neighbor of y if y can receive x signal 2-hop neighbor: a node whose signal is received by its neighbor. strict 2-hop neighbor P multipoint relay (MPR): A node selected by its neighbor x, to forward all the broadcast messages received from x, if it is not a duplicate message and if life-time is >1 multipoint relay selector (MS) A node that selected its neighbor x as a MPR X Y S Terminology M Z

65 Each node periodically broadcasts Hello messages: List of neighbors with bi-directional link List of other known neighbors. Neighbor sensing Hello messages permit each node to learn topology up to 2 hops Based on Hello messages each node selects its set of MPR s

66 Each point u has to select its set of MPR. MPR selection algorithm Goal: select in the 1-neighborhood of u ( 1 (u)) a set of nodes as small as possible which covers the whole 2-neighborhood of u ( 2 (u)), in two steps : Step 1: Select nodes of 1 (u) which cover isolated points of 2 (u). (That we call MPR 1 (u).) Step 2: Select among the nodes of 1 (u) not selected at the first step, the node which covers the highest number of points (not already covered) of 2 (u) and go on till every points of 2 (u) are covered.

67 MPR selection algorithm : example u First step: select nodes in 1 (u) which cover «isolated points» of 2 (u).

68 MPR selection algorithm : example Second step: Consider in 1 (u) only points which are not already selected at the first step MPR 1 (u) and points in 2 (u) which are not covered by the MPR 1 (u). While there exists points in 2 (u) not covered by the selected MPR, select in 1 (u), the node which covers the highest number of non-covered nodes in 2 (u). u

MPR selection algorithm: example; final result u 69

70 TC Topology control message: MPR information declaration Sent periodically. Message might not be sent if there are no updates and sent earlier if there are updates Contains: MPR Selector Table Sequence number Each node maintains a Topology Table based on TC messages Routing Tables are calculated based on Topology tables

71 Example of neighbor table One-hop neighbors Two-hop neighbors Neighbor s id State of Link Neighbor s id Access through B Bidirectional E C G Unidirectional D C C MPR Also every entry in the table has a timestamp, after which the entry in not valid

72 Topology Table Destination address Destination s MPR MPR Selector sequence number Holding time MPR Selector in the received TC message Last-hop node to the destination. Originator of TC message

73 Upon receipt of TC message: Topology Table (cont) If there exist some entry to the same destination with higher Sequence Number, the TC message is ignored If there exist some entry to the same destination with lower Sequence Number, the topology entry is removed and the new one is recorded If the entry is the same as in TC message, the holding time of this entry is refreshed If there are no corresponding entry the new entry is recorded

74 All nodes manage a routing table Its structure is: 1. R_dest_addr R_next_addr R_dist R_iface_addr 2. R_dest_addr R_next_addr R_dist R_iface_addr 3.,,,,,,,, Routing table Each entry indicates that node R_dest_addr is R_dist hops away, and the first hop is through R_next_addr. This node can be reached through the local interface R_iface_addr There is an entry for each destination in the network The table is updated each time a change is detected in: the link set, the neighbor set, the 2-hop neighbor set, the topology set, the Multiple Interface Association Information Base, The table is built using a shortest path algorithm

76 Location-Aided Routing (LAR) Exploits location information to limit scope of route request flood Location information may be obtained using GPS Expected Zone is determined as a region that is expected to hold the current location of the destination Expected region determined based on potentially old location information, and knowledge of the destination s speed Route requests limited to a Request Zone that contains the Expected Zone and location of the sender node

77 X = last known location of node D, at time t 0 Expected Zone in LAR Y = location of node D at current time t 1, unknown to node S r = (t 1 - t 0 ) * estimate of D s speed r X Expected Zone Y

78 Request Zone in LAR Only nodes within the request zone forward route requests Node A does not forward RREQ, but node B does (see previous slide) Request zone explicitly specified in the route request Each node must know its physical location to determine whether it is within the request zone Network Space Request Zone r X A S B Y

79 Forwarding in LAR Only nodes within the request zone forward route requests 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

80 Advantages reduces the scope of route request flood reduces overhead of route discovery Location Aided Routing (LAR) Disadvantages Nodes need to know their physical locations Does not take into account possible existence of obstructions for radio transmissions

81 Geographic Distance Routing (GEDIR) Location of the destination node is assumed known Each node knows location of its neighbors Each node forwards a packet to its neighbor closest to the destination Route taken from S to D shown below A H D S B C G E F obstruction

82 Geographic Distance Routing (GEDIR) The algorithm terminates when same edge traversed twice consecutively Algorithm fails to route from S to E Node G is the neighbor of C who is closest from destination E, but C does not have a route to E A H D S B C G E F obstruction

83 Zone routing protocol combines Zone Routing Protocol (ZRP) Proactive protocol: which pro-actively updates network state and maintains route regardless of whether any data traffic exists or not Reactive protocol: which only determines route to a destination if there is some data to be sent to the destination All nodes within hop distance at most d from a node X are said to be in the routing zone of node X All nodes at hop distance exactly d are said to be peripheral nodes of node X s routing zone Intra-zone routing: Pro-actively maintain state information for links within a short distance from any given node Routes to nodes within short distance are thus maintained proactively (using, say, link state or distance vector protocol) Inter-zone routing: Use a route discovery protocol for determining routes to far away nodes. Route discovery is similar to DSR with the exception that route requests are propagated via peripheral nodes.

84 ZRP: Example with Zone Radius = d = 2 S performs route discovery for D B F A S C E D Denotes route request

85 ZRP: Example with d = 2 S performs route discovery for D B F A S C E D Denotes route reply E knows route from E to D, so route request need not be forwarded to D from E

86 ZRP: Example with d = 2 S performs route discovery for D B F A S C E D Denotes route taken by Data

87 Landmark Routing (LANMAR) for MANET with Group Mobility A landmark node is elected for a group of nodes that are likely to move together A scope is defined such that each node would typically be within the scope of its landmark node Each node propagates link state information corresponding only to nodes within it scope and distance-vector information for all landmark nodes Combination of link-state and distance-vector Distance-vector used for landmark nodes outside the scope No state information for non-landmark nodes outside scope maintained

88 LANMAR Routing to Nodes Within Scope Assume that node C is within scope of node A H C D G A B E F Routing from A to C: Node A can determine next hop to node C using the available link state information

89 LANMAR Routing to Nodes Outside Scope Routing from node A to F, which is outside A s scope Let H be the landmark node for node F H C D G A B E F Node A somehow knows that H is the landmark for C Node A can determine next hop to node H using the available distance vector information

90 LANMAR Routing to Nodes Outside Scope Node D is within scope of node F H C D G A B E F Node D can determine next hop to node F using link state information The packet for F may never reach the landmark node H, even though initially node A sends it towards H

91 LUNAR (Lightweight Underlay Network Ad hoc Routing) Instead of having routing protocol logic that actively maintains and repairs existing routing paths, LUNAR always establishes paths from scratch. LUNAR floods the network every 3 s for discovering a route. During the 3 s interval, all data packets are shipped over the same path and no attempts are made to discover lost packets or to monitor link changes.