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 propos ed

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 Introduction Routing Protocol for MANET Table-Driven/ Proactive Hybrid Distance Vector Link- State ZRPDSR AODV TORA LANMAR CEDAR DSDVOLSR TBRPF FSR STAR MANET: Mobile Ad hoc Network (IETF working group) On-Demand- driven/Reactive Clusterbased/ Hierarchical 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 algorith m  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 Cluster Gateway Switch Routing (CGSR)  Table-driven for inter-cluster routing  Uses DSDV for intra-cluster routing M2 C3 C2 C1

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 enou gh ” route to destination) replies a route reply pack et (RREP)

18 AODV N2 N4 N1 N3 N5 N6 N7 N8 Source Destination N2 N4 N1 N3 N5 N6 N7 N8 Source Destination 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 ac tive 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 DSR N2 N4 N1 N3 N5 N6 N7 N8 N1 N1-N2 N1-N3-N4 N1-N3-N4-N7 N1-N3-N4-N6 N1-N3 N1-N3-N4 N1-N2-N5 N2 N4 N1 N3 N5 N6 N7 N8 N1-N2-N5-N 8 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 Radius = r Hops Zone of Node Y Node X Zone of Node X Node Z Zone of Node Z Border Node Bordercasting Zone Routing Protocol (ZRP)

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

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 assu mption  Route discovery is initiated when:  S doesn’t know a route to D  Previous route from S to D is broken 26

LAR - Definitions  Expected Zone  S knows the location L of D in t 0  Current time t 1  The location of D in t 1 is the expected zone  Request Zone  Flood with a modification  Node S defines a request zone for the route request 27

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

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

Restricted Directional Flooding  Distance Routing effect Algorithm for mobility (DREAM)  Sender will forward the packet to all one-hop neigh bors that lie in the direction of destination  Expected region is a circle around the position of d estination 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 timest amp of the position information source has about d estination, and Vmax is the maximum speed that a node may travel in the ad hoc network  The direction toward destination is defined by the l ine between source and destination and the angle  30 From ECE 5970 Class

DREAM 31

32 Power-Aware Routing (PAR) +–+– +–+– +–+– +–+– +–+– +–+– SRC N1 N2 DES T N4 N3

33 OLSR - Overview  OLSR  Inherits Stability of Link-state protocol  Selective Flooding  only MPR retransmit 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 OLSR – Multipoint relays (cont.) Figure 1. Diffusion of a broadcast message using multipoint relays 4 retransmission to diffuse a message up to 2 hops MPR(Retransmission node)

37 OLSR – Multipoint relays (cont.) Node 1 Hop Neighbors 2 Hop Neighbors MPR(s) B A,C,F,G D,E C A B C D E F G Figure 2. Network example for MPR selection

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

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.) Message typeVtimeMessage size Originator Address Time To LiveHop countMessage Sequence Number ReservedHtime Willingness Link codeReservedLink message size Neighbor Interface Address Neighbor interface Address … ReservedHtime Willingness Link codeReservedLink message size Neighbor interface address … Table 1. Hello Message Format in OLSR Link typeNeighbor type

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 …… MPRC UnidirectionalG BidirectionalB State of LinkNeighbor’s id Two-hop neighbors …… C D CE Access thoughNeighbor ’ s id 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.) Destination addressDestination’s MPRMPR Selector sequence number Holding time MPR Selector in the received TC message Last-hop node to the destination. Originator of TC message Table 3. Topology table

47 Protocol functioning – MPR information declaration (cont.) G F E D CB MS(C) = {B,D,E}MPR(B) = {A,C} Figure 4. TC message and Topology table Send TC message {B,D,E} build the 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 Protocol functioning – MPR information declaration (cont.) S B D M X Y Z P A Send TC message Dest’ address Dest’ MPR MPR Selector sequence XM1 YM1 ZM1.. S’ Topology table TC’ originator MPR selector MPR selector sequence MX2 MY2 MZ2 MR2 TC message ( M send to S) R Figure 5. Topology table update

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

51 Protocol functioning – Routing table calculation (cont.) Source Destination (last-hop, destination) Figure 5. Building a route from topology table

52 conclusion  OLSR protocol is proactive or table driven in nature  Advantages  Route immediately available  Minimize flooding by using MPR  OLSR protocol is suitable for large and dense networks

53 Current routing protocols  Many do not consider energy conservation  lead to partitions  shorten network life  fairness to intermediate nodes not incorporated  fail to work well in both sparse and dense networks

54 Interesting Research Topics  Energy Awareness Routing  Multipath Routing  more paths used to send information, more reliable the trans mission  Clustering (Hierarchical Routing)  dynamic management of subnetworks

55 More Research Topics  Topology Control  adjustment of transmission power to simplify routing  Internetworking  managing wired and wireless networks  Heterogeneous Networks  Different devices on the network have different capabilities  Content Aware Networks  Location of services within the network (Printers)

56 References  Ad Hoc Mobile Wireless Networks – Protocols and Syste m, C-K Toh, Prentice Hall, 2002, ISBN:  “Introduction to Ad Hoc Networking”, Prof. Yu-Chee Ts eng  “Optimized Link State Routing Protocol for Ad Hoc Networks, Jacquet”, p and park gi won  “Ad Hoc Network”, Wireless LANs, June – September 2009, Asso. Prof. Anan Phonphoem, Ph.D.