Ad Hoc Networks

1. Ad Hoc Networks Cholatip Yawut Faculty of Information Technology King Mongkut's University of Technology North Bangkok

2. IEFT MANET Working Group • Goals • standardize an interdomain unicast (IP) routing protocol • define modes of efficient operation • support both static and dynamic topologies • A dozen candidate routing protocols have been proposed

3. Routing ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Ants Searching for Food ? from Prof. Yu-Chee Tseng’s slides

4. Routing (Ants’ scenario)

5. Three Main Issues in Ants’ Life • Route Discovery: • searching for the places with food • Packet Forwarding: • delivering foods back home • Route Maintenance: • when foods move to new place

6. Routing Protocol for MANET Table-Driven/ Proactive Hybrid On-Demand-driven/Reactive Clusterbased/ Hierarchical Distance Vector Link- State ZRP DSR AODV TORA LANMAR CEDAR DSDV OLSR TBRPF FSR STAR MANET: Mobile Ad hoc Network (IETF working group) Introduction Ref: Optimized Link State Routing Protocol for Ad Hoc Networks Jacquet, p and park gi won

7. Reactive versus Proactive routing approach • Proactive Routing Protocols • Periodic exchange of control messages • + immediately provide the required routes when needed • - Larger signalling traffic and power consumption. • Reactive Routing Protocols • Attempts to discover routes only on-demand by flooding • + Smaller signalling traffic and power consumption. • - A long delay for application when no route to the destination available

8. Routing Protocols • Proactive (Global/Table Driven) • route determination at startup • maintain using periodic update • Reactive (On-demand) • route determination as needed • route discovery process • Hybrid • combination of proactive and reactive

9. Proactive • Destination-sequenced distance vector (DSDV) • Wireless routing protocol (WRP) • Global state routing (GSR) • Fisheye state routing (FSR) • Source-tree adaptive routing (STAR) • Distance routing algorithm for mobility (DREAM) • Cluster-head gateway switch routing (CGSR) • OLSR (Optimized Link State Routing)

10. Reactive • Associativity-base routing (ABR) • Dynamic source routing (DSR) • Ad hoc on-demand distance vector (AODV) • Temporally ordered routing algorithm (TORA) • Routing on-demand acyclic multi-path (ROAM) • Light-weight mobile routing (LMR) • Signal stability adaptive (SSA) • Cluster-based routing protocol (CBRP)

11. Hybrid • Zone routing protocol (ZRP) • Zone-based hierarchical link state (ZHLS) • Distributed spanning trees (DST) • Distributed dynamic routing (DDR) • Scalable location update routing pro. (SLURP)

12. Flooding • Simplest of all routing protocols • Send all info to everybody • If data not for you, send to all neighbors • Robust • destination is guaranteed to receive data • Resource Intensive • unnecessary traffic • load increases, network performance drops quickly

13. Routing Examples • Destination Sequenced Distance Vector (DSDV) • Cluster Gateway Switch Routing (CGSR) • Ad hoc On-demand Distance Vector (AODV) • Dynamic Source Routing (DSR) • Zone Routing Protocol (ZRP) • Location-Aided Routing (LAR) • Distance Routing effect Algorithm for mobility (DREAM) • Power-Aware Routing (PAR)

14. Destination Sequenced Distance Vector (DSDV) • Table-driven • Based on the distributed Bellman-Ford routing algorithm • Each node maintains a routing table • Routing hops to each destination • Sequence number

15. DSDV • Problem • a lot of control traffic in the network • Solution: two types of route update packets • full dump (All available routing info) • incremental (Only changed info)

16. C2 C1 C3 Cluster Gateway Switch Routing (CGSR) • Table-driven for inter-cluster routing • Uses DSDV for intra-cluster routing M2

17. Ad hoc On-demand Distance Vector (AODV) • On-demand driven • Nodes that are not on the selected path do not maintain routing information • Route discovery • source broadcasts a route request packet (RREQ) • destination (or intermediate node with “fresh enough” route to destination) replies a route reply packet (RREP)

18. Destination N2 N8 Destination N5 N2 N8 N5 Source N1 N7 N4 Source N1 N7 N4 N3 N6 N3 N6 AODV RREQ RREP

19. AODV • Problem • a node along the route moves • Solution • upstream neighbor notices the move • propagates a link failure notification message to each of its active upstream neighbors • source receives the message and re-initiate route discovery

20. Dynamic Source Routing (DSR) • On-demand driven • Based on the concept of source routing • Required to maintain route caches • Two major phases • Route discovery (flooding) • Route maintenance • A route error packet

21. N1-N2 N1-N2-N5 N8 N2 N5 N1 N1-N3-N4 N1-N3-N4-N7 N1-N2-N5-N8 N1-N2-N5-N8 N2 N8 N1 N7 N5 N4 N1-N2-N5-N8 N1-N3-N4 N1 N1-N3 N1 N7 N1-N3-N4-N6 N4 N3 N1-N3-N4 N6 N3 N6 DSR Route Discovery Route Reply

22. Modified DSR • Route information determined by the current network conditions • number of hops • congestion • node energy • Other considerations • fairness • number of route requests

23. Zone Routing Protocol (ZRP) • Hybrid protocol • On-demand • Proactive • ZRP has three sub-protocols • Intrazone Routing Protocol (IARP) • Interzone Routing Protocol (IERP) • Bordercast Resolution Protocol (BRP)

24. Zone Routing Protocol (ZRP) Zone of Node Y Border Node Zone Radius = r Hops Border Node Node X Zone of Node Z Node Z Zone of Node X Bordercasting

25. Location-Aided Routing (LAR) • Location information via GPS • Shortcoming (maybe not anymore 2005) • GPS availability is not yet worldwide • Position information come with deviation

26. Location-Aided Routing (LAR) • Each node knows its location in every moment • Using location information for route discovery • Routing is done using the last known location + an assumption • Route discovery is initiated when: • S doesn’t know a route to D • Previous route from S to D is broken

27. LAR - Definitions • Expected Zone • S knows the location L of D in t0 • Current time t1 • The location of D in t1 is the expected zone • Request Zone • Flood with a modification • Node S defines a request zone for the route request

28. Expected Zone (Xd+R, Yd+R) Request Zone LAR Destination (Xd,Yd) R source(Xs,Ys)

29. Distance Routing effect Algorithm for mobility (DREAM) • Position-based • Each node • maintains a position database • regularly floods packets to update the position • Temporal resolution • Spatial resolution

30. Restricted Directional Flooding • Distance Routing effect Algorithm for mobility (DREAM) • Sender will forward the packet to all one-hop neighbors that lie in the direction of destination • Expected region is a circle around the position of destination as it is known to source • The radius r of the expected region is set to (t1-t0)*Vmax, where t1 is the current time, t0 is the timestamp of the position information source has about destination, and Vmax is the maximum speed that a node may travel in the ad hoc network • The direction toward destination is defined by the line between source and destination and the angle  From ECE 5970 Class

31. DREAM

32. N2 N1 SRC DEST + – + – + – + – + – + – N3 N4 Power-Aware Routing (PAR)

33. OLSR - Overview • OLSR • Inherits Stability of Link-state protocol • Selective Flooding • only MPRretransmit control messages: • Minimize flooding • Suitable for large and dense networks

34. OLSR – Multipoint relays (MPRs) • MPRs = Set of selected neighbor nodes • Minimize the flooding of broadcast packets • Each node selects its MPRs among its on hop neighbors • The set covers all the nodes that are two hops away • MPR Selector = a node which has selected node as MPR • The information required to calculate the multipoint relays : • The set of one-hop neighbors and the two-hop neighbors • Set of MPRs is able to transmit to all two-hop neighbors • Link between node and it’s MPR is bidirectional.

35. OLSR – Multipoint relays (cont.) • To obtain the information about one-hop neighbors : • Use HELLO message (received by all one-hop neighbors) • To obtain the information about two-hop neighbors : • Each node attaches the list of its own neighbors • Once a node has its one and two-hop neighbor sets : • Can select a MPRs which covers all its two-hop neighbors

36. MPR(Retransmission node) OLSR – Multipoint relays (cont.) 4 retransmission to diffuse a message up to 2 hops Figure 1. Diffusion of a broadcast message using multipoint relays

37. Node1 Hop Neighbors2 Hop NeighborsMPR(s) BA,C,F,GD,E C OLSR – Multipoint relays (cont.) E D F A C G B Figure 2. Network example for MPR selection

38. E F H MS(A) = {B,H,I} A C B D I MS(C) = {B,D,E} MPR(B) = {A,C} G Figure 3. MPR과 MPR Selector Set OLSR – Multipoint relays (cont.)

39. Protocol functioning – Neighbor sensing • Each node periodically broadcasts its HELLO messages: • Containing the information about its neighbors and their link status • Hello messages are received by all one-hop neighbors • HELLO message contains: • List of addresses of the neighbors to which there exists a valid bi-directional link • List of addresses of the neighbors which are heard by node( a HELLO has been received ) • But link is not yet validated as bi-directional

40. Protocol functioning – Neighbor sensing (cont.) Table 1. Hello Message Format in OLSR

41. Protocol functioning – Neighbor sensing (cont.) • HELLO messages : • Serves Link sensing • Permit each node to learn the knowledge of its neighbors up to two-hops (neighbor detection) • On the basis of this information, each node performs the selection of its multipoint relays (MPR selection signaling) • Indicate selected multipoint relays • On the reception of HELLO message: • Each node constructs its MPR Selector table

42. Protocol functioning – Neighbor sensing ( cont.) • In the neighbor table: • Each node records the information about its on hop neighbor and a list of two hop neighbors • Entry in the neighbor table has an holding time • Upon expiry of holding time, removed • Contains a sequence number value which specifies the most recent MPR set • Every time updates its MPR set, this sequence number is incremented

43. Protocol functioning – Neighbor sensing • Example of neighbor table One-hop neighbors Two-hop neighbors Neighbor’s id State of Link Neighbor’s id Access though B Bidirectional E C G Unidirectional D C C MPR … … … … Table 2. Example of neighbor table

44. Protocol functioning – Multipoint relay selection • Each node selects own set of multipoint relays • Multipoint relays are declared in the transmitted HELLO messages • Multipoint relay set is re-calculated when: • A change in the neighborhood( neighbor is failed or add new neighbor ) • A change in the two-hop neighbor set • Each node also construct its MPR Selector table with information obtained from the HELLO message • A node updates its MPR Selector set with information in the received HELLO messages

45. Protocol functioning – MPR information declaration • TC – Topology control message: • In order to build intra-forwarding database • Only MPR nodes forward periodically to declare its MPR Selector set • Message might not be sent if there are no updates • Contains: • MPR Selector • Sequence number • Each node maintains a Topology Table based on TC messages • Routing Tables are calculated based on Topology tables

46. Protocol functioning – MPR information declaration (cont.) Last-hop node to the destination. Originator of TC message MPR Selector in the received TC message Table 3. Topology table

47. E F C B Send TC message D {B,D,E} build the topology table MS(C) = {B,D,E} MPR(B) = {A,C} G Protocol functioning – MPR information declaration (cont.) Figure 4. TC message and Topology table

48. Protocol functioning – MPR information declaration (cont.) • Upon receipt of TC message: • 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

49. S P M Z X Y R B A Send TC message D Protocol functioning – MPR information declaration (cont.) S’ Topology table Figure 5. Topology table update TC message ( M send to S)

50. Protocol functioning – Routing table calculation • Each node maintains a routing table to all known destinations in the network • After each node TC message receives, store connected pairs of form ( last-hop, node) • Routing table is based on the information contained in the neighbor table and the topology table • Routing table: • Destination address • Next Hop address • Distance • Routing Table is recalculated after every change in neighbor table or in topology table