1. Routing in Ad-hoc Networks19 th CEENet Workshop Budapest, 2004 Routing in Ad-hoc Networks 9 th CEENet Workshop on Network Technology NATO ANW Iskra Djonova Popova (iskra.popova@mh.se)

2. Routing in Ad-hoc Networks29 th CEENet Workshop Budapest, 2004 Contents:  Ad-hoc Networks  Problems with Routing  Destination Sequenced Distance Vector (DSDV)  (Clusterhead Gateway Switch Routing (CGSR)  Dynamic Source Routing (DSR)  Location Aided Routing (LAR)  Classification of the Routing Protocols  Standardization and Future Work

3. Routing in Ad-hoc Networks39 th CEENet Workshop Budapest, 2004 Ad-hoc Networks  Two types of wireless network:  Infrastructured  the mobile node can move while communicating  the base stations are fixed  as the node goes out of the range of a base station, it gets into the range of another base station  Infrastructureless or ad-hoc  the mobile node can move while communicating  there are no fixed base stations  all the nodes in the network need to act as routers  In Latin “ad-hoc” literally means “for this purpose only”. Then an ad-hoc network can be regarded as “spontaneous network”

4. Routing in Ad-hoc Networks49 th CEENet Workshop Budapest, 2004  Infrastructured network Pen computer Radio tower Laptop computer Radio tower Infrastructure (Wired line) Desktop computer Laptop computer Ad-hoc Networks

5. Routing in Ad-hoc Networks59 th CEENet Workshop Budapest, 2004  Infrastructurless (ad-hoc) network or MANET (Mobile Ad-hoc NETwork) Ad-hoc Networks PDA Pen computer Laptop computer PDA

6. Routing in Ad-hoc Networks69 th CEENet Workshop Budapest, 2004  Single hop – nodes are in their reach area and can communicate directly  Multi hop – some nodes are far and cannot communicate directly. The traffic has to be forwarded by other intermediate nodes.  Classification of ad-hoc networks Ad-hoc Networks

7. Routing in Ad-hoc Networks79 th CEENet Workshop Budapest, 2004  Characteristics of an ad-hoc network  Collection of mobile nodes forming a temporary network  Network topology changes frequently and unpredictably  No centralized administration or standard support services  Each host is an independent router  Hosts use wireless RF transceivers as network interface  Number of nodes 10 to 100 or at most 1000 Ad-hoc Networks

8. Routing in Ad-hoc Networks89 th CEENet Workshop Budapest, 2004  Why we need ad-hoc networks?  Setting up of fixed access points and backbone infrastructure is not always viable  Infrastructure may not be present in a disaster area or war zone  Infrastructure may not be practical for short-range radios; Bluetooth (range ~ 10m)  Do not need backbone infrastructure support  Are easy to deploy  Useful when infrastructure is absent, destroyed or impractical Ad-hoc Networks

9. Routing in Ad-hoc Networks99 th CEENet Workshop Budapest, 2004 Ad-hoc Networks  Example applications of ad hoc networks:  emergency search-and-rescue operations,  meetings or conventions in which persons wish to quickly share information,  data acquisition operations in inhospitable terrain,  local area networks in the future.

10. Routing in Ad-hoc Networks109 th CEENet Workshop Budapest, 2004 Ad-hoc Networks Mobile Ad Hoc Networking is a multi-layer problem ! Physical/Link Layer Network Layer Transport Layer Application Layer - Routing - Addressing - Location Management - Power Control - Multiuser Detection - Channel Access - TCP - Quality of Service - Security - Service Discovery - Location-dependent Application

11. Routing in Ad-hoc Networks119 th CEENet Workshop Budapest, 2004  Is it possible to use standard routing protocols?  Distance-vector protocols  Slow convergence due to “Count to Infinity” Problem  Creates loops during node failure, network partition or congestion  Link state protocols  Use flooding technique and create excessive traffic and control overhead  Require a lot of processor power and therefore high power consumption Problems with Routing

12. Routing in Ad-hoc Networks129 th CEENet Workshop Budapest, 2004 Problems with Routing  Limitations of the Wireless Network  packet loss due to transmission errors  variable capacity links  frequent disconnections/partitions  limited communication bandwidth  Broadcast nature of the communications  Limitations Imposed by Mobility  dynamically changing topologies/routes  lack of mobility awareness by system/applications  Limitations of the Mobile Computer  short battery lifetime  limited capacities

13. Routing in Ad-hoc Networks139 th CEENet Workshop Budapest, 2004 DSDV  DSDV (Destination Sequenced Distance Vector)  Each node sends and responds to routing control message the same way  No hierarchical structure  Avoids the resource costs involved in maintaining high-level structure  Scalability may become an issue in larger networks

14. Routing in Ad-hoc Networks149 th CEENet Workshop Budapest, 2004  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! DSDV

15. Routing in Ad-hoc Networks159 th CEENet Workshop Budapest, 2004 Traditional Distance vector tables C Dest.NextMetric… AA1 BB0 CC2 Dest.NextMetric… AA0 BB1 CB3 12 Dest.NextMetric… AB3 BB2 CC0 BA DSDV

16. Routing in Ad-hoc Networks169 th CEENet Workshop Budapest, 2004 (A, 1) (B, 0) (C, 1) (A, 1) (B, 0) (C, 1) Distance Vector Updates C Dest.NextMetric… AA1 BB0 CC1 Dest.NextMetric… AA0 BB1 CB3 2 1 1 Dest.NextMetric… AB3 2 BB1 CC0 BA B broadcasts the new routing information to his neighbors Routing table is updated DSDV

17. Routing in Ad-hoc Networks179 th CEENet Workshop Budapest, 2004 (D, 0) (A, 2) (B, 1) (C, 0) (D, 1) (A, 1) (B, 0) (C, 1) (D, 2) Distance Vector – New Node joins the network C 11 BAD 1 broadcasts to update tables of C, B, A with new entry for D Dest.NextMetric… AB2 BB1 CC0 DD1 Dest.NextMetric… AA1 BB0 CC1 DC2 Dest.NextMetric… AA0 BB1 CB2 DB3 DSDV

18. Routing in Ad-hoc Networks189 th CEENet Workshop Budapest, 2004 Distance Vector – Broken link C 11 BA D 1 Dest. c NextMetric… ……… DC2 Dest.NextMetric… ……… DB3 Dest.NextMetric… ……… DB 1 Dest.NextMetric… ……… DD  DSDV

19. Routing in Ad-hoc Networks199 th CEENet Workshop Budapest, 2004 (D, 2) Distance Vector - Loops C 11 BA D 1 Dest.NextMetric… ……… DB3 Dest.NextMetric… ……… DC2 Dest.NextMetric… ……… DB 3 DSDV

20. Routing in Ad-hoc Networks209 th CEENet Workshop Budapest, 2004 (D,2) (D,4) (D,3) (D,5) (D,2) (D,4) Distance vector - Count to Infinity C 11 BA D 1 Dest.NextMetric… ……… DB3, 5, … Dest.NextMetric… ……… DB 3, 5, … Dest. c NextMetric… ……… DC2, 4, 6… DSDV

21. Routing in Ad-hoc Networks219 th CEENet Workshop Budapest, 2004  Traditional Distance Vector are not suited for ad-hoc networks!  Loops  Bandwidth reduction in network  Unnecessary work for loop nodes  Count to Infinity  Very slow adaptation to topology changes.  Solution -> Introduce destination sequence numbers DSDV

22. Routing in Ad-hoc Networks229 th CEENet Workshop Budapest, 2004  DSDV keeps the simplicity of traditional Distance Vector Protocols  DSDV need to guarantee loop freeness  New Table Entry for Destination Sequence Number  DSDV need to allow fast reaction to topology changes  Make immediate route advertisement on significant changes in routing table  but wait with advertising of unstable routes (damping fluctuations) DSDV

23. Routing in Ad-hoc Networks239 th CEENet Workshop Budapest, 2004  Features introduced in DSDV  Sequence number originated from destination. Ensures loop freeness.  Install Time when entry was made (used to delete stale entries from table.  Stable Data Pointer to a table holding information on how stable a route is. Used to damp fluctuations in network. DestinationNextMetricSeq. NrInstall TimeStable Data AA0A-550001000Ptr_A BB1B-102001200Ptr_B CB3C-588001200Ptr_C DB4D-312001200Ptr_D DSDV

24. Routing in Ad-hoc Networks249 th CEENet Workshop Budapest, 2004  Advertise to each neighbor own routing information  Destination Address  Metric = Number of Hops to Destination  Destination Sequence Number  Other info (e.g. hardware addresses)  Rules to set sequence number information  On each advertisement increase own destination sequence number (use only even numbers)  If a node is no more reachable (timeout) increase sequence number of this node by 1 (odd sequence number) and set metric = . DSDV – Route Advertisement

25. Routing in Ad-hoc Networks259 th CEENet Workshop Budapest, 2004  Update information is compared to own routing table 1. Select route with higher destination sequence number (This ensure to use always newest information from destination) 2. Select the route with better metric when sequence numbers are equal. DSDV – Route Selection

26. Routing in Ad-hoc Networks269 th CEENet Workshop Budapest, 2004 DSDV Tables C Dest.NextMetricSeq AA1A-550 BB0B-100 CC2C-588 Dest.NextMetricSeq AA0A-550 BB1B-100 CB2C-586 Dest.NextMetricSeq. AB1A-550 BB2B-100 CC0C-588 BA DSDV

27. Routing in Ad-hoc Networks279 th CEENet Workshop Budapest, 2004 (A, 1, A-550) (B, 0, B-102) (C, 1, C-588) (A, 1, A-550) (B, 0, B-102) (C, 1, C-588) DSDV Route Advertisement CBA B increases Seq.Nr from 100 -> 102 B broadcasts routing information to Neighbors A, C including destination sequence numbers Dest.NextMetricSeq AA0A-550 BB1B-102 CB2C-588 Dest.NextMetricSeq AA1A-550 BB0B-102 CC1C-588 Dest.NextMetricSeq. AB2A-550 BB1B-102 CC0C-588 DSDV

28. Routing in Ad-hoc Networks289 th CEENet Workshop Budapest, 2004  DSDV Respond to topology changes  Immediate advertisements  Information on new routes, broken Links, metric change is immediately propagated to neighbors.  Full/Incremental Update:  Full Update: Send all routing information from own table.  Incremental Update: Send only entries that has changed. (Make it fit into one single packet) DSDV

29. Routing in Ad-hoc Networks299 th CEENet Workshop Budapest, 2004 (D, 0, D-000) When new node joins the network CBAD Dest.NextMetricSeq. AA0A-550 BB1B-104 CB2C-590 Dest.NextMetricSeq. AA1A-550 BB0B-104 CC1C-590 Dest.NextMetricSeq. AB2A-550 BB1B-104 CC0C-590 DD1D-000 1. D broadcast for first time Send Sequence number D-000. 2. Insert entry for D with sequence number D-000. Then immediately broadcast own table. DSDV

30. Routing in Ad-hoc Networks309 th CEENet Workshop Budapest, 2004 (A, 2, A-550) (B, 1, B-102) (C, 0, C-592) (D, 1, D-000) (A, 2, A-550) (B, 1, B-102) (C, 0, C-592) (D, 1, D-000) (New node (cont.) CBAD Dest.NextMetricSeq. AA1A-550 BB0B-102 CC1C-592 DC2D-000 Dest.NextMetricSeq. AA0A-550 BB1B-104 CB2C-590 Dest.NextMetricSeq. AB2A-550 BB1B-102 CC0C-592 DD1D-000 ……… 3. C increases its sequence number to C-592 then broadcasts its new table. 4. B gets this new information and updates its table……. DSDV

31. Routing in Ad-hoc Networks319 th CEENet Workshop Budapest, 2004 (D, 2, D-100) No loops, no count to infinity CBA D 1 Dest. c NextMetricSeq. ……… DC2D-100 Dest.NextMetricSeq. ……… DB3D-100 Dest.NextMetricSeq. ……… DD  D-101 1. Node C detects broken Link: -> Increase Seq. Nr. by 1 (only case where not the destination sets the sequence number -> odd number) 2. B does its broadcast -> no affect on C (C knows that B has stale information because C has higher seq. number for destination D) -> no loop -> no count to infinity DSDV

32. Routing in Ad-hoc Networks329 th CEENet Workshop Budapest, 2004 (D, , D-101) Immediate Advertisement CBA D Dest. c NextMetricSeq. ……… DC3D-100 Dest.NextMetricSeq. ……… DB4D-100 Dest.NextMetricSeq. ……… DB 1 D-100 Dest.NextMetricSeq. ……… DD 1 D-100 DD  D-101 1. Node C detects broken link: -> Increase Seq. Nr. by 1 (only case where not the destination sets the sequence number -> odd number) 3. Immediate propagation B to A: (update information has higher Seq. Nr. -> replace table entry) 2. Immediate propagation C to B: (update information has higher Seq. Nr. -> replace table entry) Dest. c NextMetricSeq. ………... DC 2 D-100 DC  D-101 Dest.NextMetricSeq. ………... DB 3 D-100 DB  D-101 DSDV

33. Routing in Ad-hoc Networks339 th CEENet Workshop Budapest, 2004 Problem of Fluctuations  Entry for D in A: [D, Q, 14, D-100]  D makes broadcast with Seq. Nr. D-102  A receives from P Update (D, 15, D-102) -> Entry for D in A: [D, P, 15, D-102] A must propagate this route immediately.  A receives from Q Update (D, 14, D-102) -> Entry for D in A: [D, Q, 14, D-102] A must propagate this route immediately. This can happen every time D or any other node does its broadcast and lead to unnecessary route advertisements in the network, so called fluctuations. A D Q P 10 Hops11 Hops (D,0,D-102) DSDV

34. Routing in Ad-hoc Networks349 th CEENet Workshop Budapest, 2004  Advantages  Simple (almost like Distance Vector)  Loop free through destination seq. numbers  No latency caused by route discovery  Disadvantages  No sleeping nodes  Bi-directional links required  Overhead: most routing information never used  Scalability is a major problem DSDV

35. Routing in Ad-hoc Networks359 th CEENet Workshop Budapest, 2004 CGSR  CSGR (Clusterhead Gateway Switch Routing)  Similar to DSDV  Based on concept of clusters and cluster heads  Routing is done via the cluster heads and gateways

36. Routing in Ad-hoc Networks369 th CEENet Workshop Budapest, 2004 CGSR  Problems with CGSR  More time is spend in selection of cluster heads and gateways  If the mobile node uses CDMA/TDMA then it can take some time to get permission to send packets

37. Routing in Ad-hoc Networks379 th CEENet Workshop Budapest, 2004 DSR  DSR (Dynamic Source Routing)  Similar to the source routing in traditional networks  A node maintains route cache containing the routes it knows  Includes route discovery on request and route maintenance when needed

38. Routing in Ad-hoc Networks389 th CEENet Workshop Budapest, 2004 DSR  Route discovery  The source sends a broadcast packet which contains source address, destination address, request id and path.  If the host receiving this packet, saw this packet before, discards it.  Otherwise, it looks up its route caches to look for a route to destination. If a route is not found, it appends its address into the packet and rebroadcasts it.  If the route is found, it sends a reply packet to the source node.  The route will be eventually found when the request packet reaches the destination

39. Routing in Ad-hoc Networks399 th CEENet Workshop Budapest, 2004 Source DSR RREQ (Route request) 4 3 6 5 1 2 RREQ(1,5,{1,2,4}) Routecache (3,5) > {3,6,5}... Routecache... Routecache... RREQ(1,5,{1}) RREQ(1,5,{1,2}) Routecache... Routecache... (source, destination, path) Destination

40. Routing in Ad-hoc Networks409 th CEENet Workshop Budapest, 2004 DSR  How to send a reply packet?  If the destination has a route to the source in its cache, use it  Else if symmetric links are supported, use the reverse of the route record  Else, if symmetric links are not supported, the destination initiate route discovery to source

41. Routing in Ad-hoc Networks419 th CEENet Workshop Budapest, 2004 DSR 4 3 6 5 1 2 Routecache (3,1) > {3,2,1} (3,2) > {3,2} (3,5) > {3,6,5}... Routecache... Routecache (5,1) > {5,4,2,1} (5,2) > {5,4,2} (5,4) > {5,4}... Routecache (2,1) > {2,1} (2,4) > {2,4}... Routecache (1,5) >{1,2,4,5}, {1,2,3,6,5}... RREP(5,1,{1,2,4,5}) RREP(5,1,{1,2,4,5}) RREP(5,1,{1,2,4,5})RREP(3,1,{1,2,3,6,5}) RREP (Route reply) Source, destination, source route) Source Destination

42. Routing in Ad-hoc Networks429 th CEENet Workshop Budapest, 2004 DSR  Route maintenance  Whenever a node transmits a data packet, a route reply or a route error, it must verify that the next hop correctly receives the packet.  If not, the node must send a route error to the node responsible for generating this route header.  The source restarts the route discovery

43. Routing in Ad-hoc Networks439 th CEENet Workshop Budapest, 2004 DSR  Advantages  Do not exchange routing update periodically, so overhead transmission is greatly reduced  Can refer to cache for the new route when link fails.  Disadvantages  Scalability problem: High route discovery latency for large network.  High mobility problem: although the packet dropped may not be substantional, the overhead traffic will increase a lot.

44. Routing in Ad-hoc Networks449 th CEENet Workshop Budapest, 2004 LAR  LAR (Location Aided Routing)  Modified flooding algorithm  Exploits location information to limit the scope of the route request flood  Location information being obtained from a GPS unit

45. Routing in Ad-hoc Networks459 th CEENet Workshop Budapest, 2004  The expected zone is defined as the region that is expected to hold the current location of the destination X r X = last known location of node D, at time t 0 r = (t 1 - t 0 ) * estimate of D’s speed LAR

46. Routing in Ad-hoc Networks469 th CEENet Workshop Budapest, 2004  The route request is limited to the Request zone.  The request zone is the smallest rectangular region that contains the expected zone and the location of the sending node. LAR

47. Routing in Ad-hoc Networks479 th CEENet Workshop Budapest, 2004 X r 1 S 2 request zone network space LAR expected zone

48. Routing in Ad-hoc Networks489 th CEENet Workshop Budapest, 2004  Only nodes within the request zone forward route request  The request zone is explicitly specified in the route request  If route discovery using the smaller request zone fails to find a route, the source node initiates another route discovery (after a timeout ) using a larger zone LAR

49. Routing in Ad-hoc Networks499 th CEENet Workshop Budapest, 2004  Implicit request zone  Node x forwards a route request received from y if x is deemed closer to the expected zone when compared to y.  This is an attempt to bring the route request physically closer to the destination node after each forwarding LAR

50. Routing in Ad-hoc Networks509 th CEENet Workshop Budapest, 2004  Proactive (table driven)  Require each node to maintain one or more tables to store routing information  Each node responds to changes in network topology by propagating updates throughout the network in order to maintain a consistent network view  DSDV, OLSR (Optimized Link State Protocol)  Reactive protocols (source initiated)  Creates routes only when desired by the source node  Once a route has been established, it is maintained by a route maintenance procedure until either the destination becomes inaccessible along every path from the source or until the route is no longer desired  DSR, AODV (Ad-hoc On-demand Distance Vector) Classification of the Routing Protocols

51. Routing in Ad-hoc Networks519 th CEENet Workshop Budapest, 2004 Proactive ApproachReactive Approach Route Latency Lower  A route is kept at all times Higher  A route is never kept when not used Routing Overhead Higher  A frequent dissemination of topology information is required Lower  Fewer control packets in general  Various simulation studies have shown that reactive protocols perform better in mobile ad hoc networks than proactive ones.  However, no single protocol works well in all environments.  Which approach achieves a better trade-off depends on the traffic and mobility patterns. Classification of the Routing Protocols

52. Routing in Ad-hoc Networks529 th CEENet Workshop Budapest, 2004  Other classification  Pro active protocols  DSDV, STAR, WRP,...  Reactive protocols  AODV, DSR, TORA,...  Hierarchical/Clustering protocols  CGSR, ZRP, CBR, FSR, LANMAR,...  Position aware protocols  GPSR, LAR, GRA, ABR,... Classification of the Routing Protocols

53. Routing in Ad-hoc Networks539 th CEENet Workshop Budapest, 2004  Standardization effort led by IETF Mobile Ad-hoc Networks (MANET) task group  http://www.ietf.org/html.charters/manet-charter.html http://www.ietf.org/html.charters/manet-charter.html  Other protocols being researched  utilize geographic, nodes provided with GPS info.  Hybrid schemes that combine reactive and pro active type of protocols Standardization and Future Work

54. Routing in Ad-hoc Networks549 th CEENet Workshop Budapest, 2004 Standardization and Future Work  Leading protocols chosen by MANET  DSR: Dynamic Source Routing  AODV: Ad-hoc On-demand Distance Vector Routing  Both are “ on demand ” protocols: route information discovered only as needed