Xiuzhen Cheng cheng@gwu

1. Xiuzhen Chengcheng@gwu.edu Csci388Wireless and Mobile Security – A Survey on Ad Hoc Routing Protocols

2. Outline • Introduction • Topology-based routing • Proactive & Hybrid Protocols • DSDV/WRP/GSR/FSR/LAR • ZRP • Reactive Protocols • DSR/AODV/TORA/ABR/ASR • Location-based routing

3. Collection of mobile nodes forming a temporary network No centralized administration or standard support services Each Host is an independent router Hosts use wireless RF transceivers as network interface Conferences/Meetings Search and Rescue Disaster Recovery Automated Battlefields Mobile Ad-Hoc Network

4. MaNet Issues • Lack of a centralized entity • Network topology changes frequently and unpredictably • Channel access/Bandwidth availability • Hidden/Exposed station problem • Lack of symmetrical links • Power limitation • Multipath Fading • Doppler Effect

5. Proactive Protocols Table driven Continuously evaluate routes No latency in route discovery Large network capacity to keep info. current Most routing info. may never be used! Reactive Protocols On Demand Route discovery by some global search Bottleneck due to latency of route discovery Link breakage may not affect on-going traffic not in its vicinity MaNet Protocols – Topology Based

6. Conventional Routing Protocols • DBF (DV) shows a degradation in performance • Knows the distance to its neighbors and a distance vector. • Broadcasts its distance vector to all of its neighbors periodically • When receiving the distance vector from its neighbors, the router computes the estimated distance to all other routers • Slow convergence due to “Count to Infinity” Problem • Creates loops during node failure, network partition or congestion • Link State create excessive traffic and control overhead • Learn the neighbor’s network address; Measure the cost to each neighbor; Construct a packet telling all that just learnt; Flood this packet to all other routers; Compute the shortest path to every other router

7. MaNet Protocol Considerations • Simple, Distributed, Reliable and Efficient • Quickly adapt to changes in topology and traffic pattern • Protocol reaction to topology changes should result in minimal control overhead • Bandwidth efficient • Mobility Management involving user location management and Hand-off management • Security

8. DSDV [Perkins et al 1994] • ImprovedClassical Bellman-Ford (DV) Routing Algorithm • Routing Table: Dest id # of Hops Dest Seq. # Next Hop • Update messages: broadcasted to neighbors • Full dump packets (time-driven): complete routing table • Incremental packets (event-driven): modified entries • Each packet: routing table + broadcast seq. # • In a relatively stable network, full dump is infrequent compared to a fast-changing network • Timer: settling time of routes or weighted average time -- delay the broadcast of the routing updates

9. DSDV – Cont. • Responding to topology changes • Broken links indicated by  • Any route through a hop with a broken link is also assigned  •  routes are immediately broadcasted • Sequence number of Destination with  hops is incremented by 1 • Nodes with same or higher sequence number and finite metric broadcast their route information • Route Selection Criteria • Loop-free: most recent seq. #, best metric - # of hops • Route broadcast are asynchronous events; Fluctuations are caused due to possibility of receiving routes with worse metric first • Solution is to maintain two routing tables, one for routing and one for incremental broadcast

10. 5 4 1 3 6 8 2 7 Gateway Cluster head Node Clusterhead Gateway Switch RoutingProtocol (CGSR) [Chiang ’97] • Cluster-head election • Least Cluster Change (LCC) • Two tables: • Cluster member table: mapping from each node to its CH • Routing table: next hop to reach the destination CH • Broadcast update message for both tables periodically using DSDV algorithm • Packet routing (example) Routing from node 1 to node 8

11. Wireless Routing Protocol (WRP) • A path-finding algorithm • Utilizes information regarding the length and the predecessor-to-dest in the shortest path to each destination • Eliminates the “Count to Infinity” Problem and converges faster • An Update message is sent after processing updates from neighbors or a change in link to a neighbor is detected • Each route update from neighbor k causes route entries of other neighbors that use k to be re-computed

12. The Algorithm • Each node i maintains a Distance table (iDjk), Routing table (Destination Identifier, Distance iDj ,Predecessor Pj ,the successor Sj), link cost table (Cost, Update Period), Message Retransmission List (MRL) • Update message: <sender id, seq#, update list or ACK, response list> • Processing Updates and creating Route Table based on new information • Update from k causes i to re-compute the distances of all paths with k as the predecessor • For a destination j, a neighbor p is selected as the successor ifp->j does not include i, and is the shortest path to j

13. WRPExample

14. Global State Routing (GSR) [Chen et al ’98] • Combination of DV and LS • Global Network Topology stored in a Table • Topology Table broadcast to immediate neighbors only • Each node maintains: • A neighbor list; A topology table <link-state information & its timestamp per destination>; A next hop table: <next hop per destination>; A distance table: <shortest distance to each dest>. • Update message: • Link State/Changes updates are time triggered • Updates topology table, reconstructs routing tables, broadcasts new information.

15. Advantages/Disadvantages of GSR • Advantages : • Avoids Flooding for disconnects/reconnects • Updates are time triggered than event triggered • Greatly reduces control overhead • Disadvantages : • Hogs bandwidth since entire topology table is broadcast with each update • Link state latency depends on update interval • Can GSR be modified to rectify it’s drawbacks ?

16. Fisheye State Routing (FSR) [Iwata et at ’99] • Improvement over GSR. • The network is logically divided into “Fisheye” circles with respect to each node. The scope of the circle may be defined in terms of number of hops • Smaller update message size thus less bandwidth usage • Each node gets accurate information about its neighbors; the accuracy decreases as the distance increases • Packets are routed correctly • The closer the packet to the dest., the more accurate the route information The scope of fisheye for the center red node

17. Hierarchical State Routing (HSR) [Iwata et al ’99] • featured by • multilevel clustering and logical partitioning of mobile nodes • Hierarchical clustering • Physical level link state exchange inside each cluster; Cluster’s information exchange via gateways • Each node has hierarchical topology information • Routing information flows from higher-level to lower-level • Hierarchical address <hierarchical cluster #> 2 7 C-21 C-11 4 C-12 2 7 5 C-02 <1,1,1> 4 <2,3,8> 1 3 6 8 C-01 2 7 C-03 Gateway Cluster head Node

18. Zone-based Hierarchical Link State Routing Protocol (ZHLS) [Joa-Ng et al ’99] • Non-overlapping zones • Two topology levels: zone level and node level • Node address: <zone id, node id> • Two types of link state packets (LSP): • Node LSP: contains neighborhood information, propagates within the zone • Zone LSP: contains zone information, propagates globally • Each node knows full intra-zone node connectivity and inter-zone connectivity information • How a package is routed? • Based on its zone id and node id

19. Zone Routing Protocol • A Hybrid Routing Protocol • A Zone is defined for each node • Proactive maintenance of topology within a zone (IARP)Distance Vector or Link State • Reactive query/reply mechanism between zones (IERP)With Route Caching : Reactive Distance VectorW/O Route Caching : Source Routing • Uses ‘Bordercast’ instead of neighbor broadcast • Neighbor Discovery/Maintenance (NMD) and Border Resolution Protocol (BRP) used for query control, route accumulation etc.

20. ZRP Example 1 Hop 2 Hops Multi Hops B F A C D E G H

21. Zone Routing Protocol cont. • Routing Zone and IntrAzone Routing Protocol • Zone Radius may be based on hop count • Identity and distance of each Node within the Zone is proactively maintained • The Interzone Routing Protocol • Check if destination is within the routing zone • Bordercast a route query to all peripheral nodes • Peripheral nodes execute the same algorithm

22. Zone Routing Protocol cont. • Route Accumulation : • Provide reverse path from discovery node to source node • May employ global caching to reduce query packet length • Query Detection/Control : • Terminate Query thread in previously queried regions • Intermediate nodes update a Detected Queries Table[Query Source, ID] • Route Maintenance may be reactive or proactive

23. Ad-Hoc On-Demand Distance Vector Routing • Protocol overview and objectives • Path Discovery • Reverse Path Setup • Forward Path Setup • Route Table Management • Path Maintenance • Local Connectivity Management

24. Protocol Overview and Objectives • Pure on-demand protocol • Node does not need to maintain knowledge of another node unless it communicates with it • Routes are discovered on an as-needed basis and are maintained only as long as they are necessary • Broadcast discovery packets only when necessary • Distinguish between local connectivity and general topology maintenance • To disseminate Information about changes in local connectivity to those neighboring nodes that are likely to need it

25. Route Establishment • Initiated whenever nodes want to communicate • Route discovery • RREQ: < source addr, source seq# , broadcast id, dest addr, dest seq#, hop cnt > • RREP: <source addr, dest addr, dest seq#, lifetime> • Route table:<dest addr, dest seq#, next hop, precursors, lifetime> 7 7 2 2 5 5 s s 1 3 1 3 d d 8 8 4 6 4 6 Path taken by RREP Propagation of RREQ

26. Route Discovery • Reverse Path Setup when process up-to-date RREQ • Reverse route entry in the route table: <source addr, source seq#, hops to source, addr of node from which RREQ is received, lifetime> • Source sequence number is used to maintain freshness about reverse route to source • Forward Path Setup when process valid RREP • Forward path entry in the route table: <dest addr, addr of node from which RREP is received, hops to dest, lifetime> • Destination sequence number specified for freshness of route before accepted by source

27. Route Maintenance • Route Table Management • Route Request Expiration Timer for purging reverse paths which do not lie on source-destination route • Route Caching Timeout after which the route is considered invalid • Active_timeout Period used to determine if neighboring node is active • Active Path Maintenance • If source move causes path breakage, source re-establish route discovery by RREQ • If intermediate or destination move causes path breakage, RERR is initiated by the node upstream of the break and sent to all affected sources. How?

28. Dynamic Source Routing • Overview • Constructs a source route in packet header listing source route • Each host maintains a route cache • Route discovery used for routes not in cache • Route discovery – build route record • Route request: initiator, target, route record, unique id • Intermediate node appends its address • Destination/intermediate node sends route reply with route record 7 7 2 2 <1> <1,2> <1,3,5> 5 <1,3,5,7> 5 s s 1 3 1 3 <1,3> <1> <1,4,6> <1,4,6> d d <1> 8 8 <1,4> <1,4,6> 4 6 4 6 <1,4,6> Route reply with route record Building route record

29. Route Maintenance and Route Cache • Route Maintenance • Route error packet sent on detection of break containing addresses on both sides of error, the host that detected the error and the host to which it was trying to send the packet • All upstream node then deletes routes with that particular hop • Route Cache • Each forwarding host can add route information to cache • Nodes can operate in promiscuous mode and add information to cache from any packets that they hear • Each intermediate node having a route can send a route replypacket

30. Performance Comparison of AODV and DSR • DSR has access to significantly greater amount of routing information than AODV by virtue of source routing and promiscuous listening • DSR replies to all requests reaching a destination from a single request cycle whereas AODV only replies once thereby learning only one route • In DSR no particular mechanism to delete stale routes, unlike AODV • In AODV the route deletion causes all the nodes using that link to delete it, but in DSR only the nodes on that particular part are deleted

31. Temporally Ordered Routing Algorithm (TORA) [Park et al ’97] • Based on the concept of link reversal • Highly adaptive, efficient, scalable, distributed algorithm • Multiple routes from source to destination • For highly dynamic mobile, multi-hop wireless network • Routing Mechanism • Unique node ID and unique reference ID • Route creation: QRY (dest id) and UPD (dest id, Hi) packets • Route maintenance • Route erasure: Clear packet (CLR) is broadcasted

32. TORA – Cont. (-,-) (0,1) (-,-) (0,3) 7 7 2 2 5 5 (0,2) s (-,-) s 1 3 1 3 (0,3) (0,3) (-,-) (-,-) d d 8 8 (0,0) (0,0) 4 6 4 6 (-,-) (-,-) (0,2) (0,1) Propogation of QRY (reference level, height) Height of each node updated by UPD Route Creation in TORA

33. TORA – Cont. (0,1) (1,-1) 7 2 5 (1,0) s 1 3 (0,3) (1,-1) d 8 (0,0) 4 6 (0,2) (0,1) Re-establishing route in link failure

34. Associativity Based Routing (ABR) [Toh ’96 ’99] • New metric: degree of association stability • Beacons periodically sent to its neighbors • Updates the associativity table • Association stability means connection stability • Associativity ticks reset • Route is long-lived and free from loops, deadlock, and packet duplicates • The protocol contains 3 phases: • Route discovery: BQ-REPLY cycle • Route reconstruction (RRC): • Route deletion (RD): Source-initiated

35. ABR (cont.)

36. Signal Stability Routing (SSR) [Dube et al ’97] • New metric: signal strength between nodes and a node’s location stability • SSR consists of 2 cooperative protocols: Dynamic Routing (DRP) & Static Routing (SRP) • DRP is responsible for Signal stability table (SST) and Routing table (RT) maintenance; Packets go through DRP, then SRP; SRP forwards packets using RT • Route discovery and route maintenance • By default, only route request packets from strong channels are forwarded • When link breakage, intermediate nodes send error message to source, which then initiates a new route-search process; and sends erase message to erase the old route

37. Comparison

38. Challenges in Ad-hoc Design • Protocols still in Nascent Stage, analysis for which protocol does well in which scenario • QOS issues in Ad-hoc • TCP performance over Ad-hoc • Security in ad hoc routing • Integration of Ad-Hoc Networks in Internet • Multicasting in Ad-hoc Networks

39. Position-based routing protocols - Characteristics • Uses additional information: physical location of nodes. • Position of oneself determined by GPS or the like. • Position of destination node by a location service • Routing decision based on • Position of destination node • Position of neighboring nodes • No need to store routing tables. • Geocasting is possible. • Location Services • Centralized location service – like cellular networks – impossible! • How to position a server? Chicken-and-egg problem. • Dynamic topology – no server nearby

40. Position-based routing • To find the position of the destination: • Location service: some-for-some; some-for-all; all-for-some; all-for-all • Each node knows the position of its neighbors and itself through periodic beacon broadcast • Packet forwarding strategy • Greedy forwarding and Restricted directional flooding (next hop selection and recovery strategy); • These two try to send a packet to a closer node • Recovery strategies for reaching ‘local maximum’ • hierarchical approaches • Greedy forwarding + local non-position-based routing • Good scalability

41. DREAM • Distance Routing Effect Algorithm for Mobility framework (DREAM) • Decentralized All-for-all approach • All nodes hold positions of all nodes • Each entry contains one’s information about direction, distance, and timestamp • Each node controls accuracy • Temporal resolution: frequency • Spatial resolution: # of hops update packets leap • Not accurate at the long distance • Because of ‘distance effect’, this is reasonable (see next slide)

42. Distance Effect • The greater the distance between two nodes, • The slower the ratio of changes in position • In the picture, A which is fixed sees B and C which is moving

43. Quorum-based Location Service • Concept from ‘quorum systems’ in databases and distributed computing. • Quorum-Based Location Service • Virtual backbone contains a small subset of nodes • A quorum is a small subset of the backbone nodes • The intersection of any two quorums is non-empty • Location update in one quorum, location query in another quorum • Some-for-some approach • Most recent-timestamped one • Tradeoff between • The size of a quorum • Resilience of reachability.

44. Grid Location Services (GLS) • The area is divided into hierarchical squares, forming a quadtree • Near node (ID): the least greater than it’s own ID • Floods to all nodes in the first-order square, nearest node in nearby 3-squares • Again, floods near node in the nearby 3 next-order squares until the highest level. • Density of information decreases logarithmically as distance increases (see next slide for an example)

45. Grid Location Services (GLS) - Example

46. Homezone • Similar to the cellular phone network • Phone moves to another region; it sends periodically position info. to the home agent • Home agent forwards call to the new agent to the phone • Each virtual zone for each node • Defined by Hash(nodeID): no contact to the destination node • All nodes within a circle centered at a node must maintain position information for the node • All-for-some approach

47. Greedy Packet Forwarding • Most Forward Within R (MFR): nearest to dest. Node C • Nearest with Forward Progress (NFP): nearest to src. Node A • Minimize ∑p*f(a,b) • p = prob. of succ.trans. • f(a,b) = progress from a to b. • Compass routing: closest to the straight line S to D. Node B • Minimize spatial travel dist. • Randomly choosing: anything closer to dest. • Less accurate position info. • Less computation. S: Source D: Destination Circle indicates ‘neighborhood’

48. Greedy Packet Forwarding (cont.) • Failure case: local maximum • Selecting least backward progress can lead to a ‘loop’ • Simply, “don’t forward” • Face-2 algorithm and the perimeter routing strategy of the Greedy Perimeter Stateless Routing Protocol (GPSR) • Per packet basis (more info in it) • Enters into recovery mode • Returns into greedy mode when the packet reaches a node closer to the destination than the node when it enters into recovery mode. • Guarantees find path to destination if there is one. • Planar graphs: • No edges crossing each other • Right hand rule for a traversing a graph

49. Planar graph • Planar sckeme uses • Right-hand rule • No crossing heuristic • Parameter Probing

50. Perimeter Forwarding