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Ad Hoc Networks

Cholatip YawutFaculty of Information Technology

King Mongkut's University of Technology North Bangkok

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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

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Routing

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Ants Searching for Food

from Prof. Yu-Chee Tsengs slides

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Routing (Antsscenario)

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Three Main Issues in AntsLife

Route Discovery: searching for the places with food

Packet Forwarding:

delivering foods back home

Route Maintenance: when foods move to new place

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Introduction

Routing Protocol for

MANET

Table-Driven/

Proactive

Hybrid

Distance

Vector

Link-

State

ZRP DSR

AODV

TORA

LANMAR

CEDAR

DSDV OLSR

TBRPFFSR

STAR

MANET: Mobile Ad hoc Network

(IETF working group)

On-Demand-driven/Reactive

Clusterbased/Hierarchical

Ref: Optimized Link State Routing Protocol for Ad Hoc NetworksJacquet, p and park gi won

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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-demandby flooding

+ Smaller signalling traffic and power consumption.

- A long delay for application when no route to the destinationavailable

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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

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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)

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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)

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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)

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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

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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)

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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

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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)

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Cluster Gateway Switch Routing (CGSR)

Table-driven for inter-cluster routing Uses DSDV for intra-cluster routing

M2

C3

C2

C1

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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

ghroute to destination) replies a route reply pack

et (RREP)

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AODV

N2

N4

N1

N3

N5

N6

N7

N8

Source

Destination

N2

N4N1

N3

N5

N6

N7

N8

Source

Destination

RREQ

RREP

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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

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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

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DSR

N2

N4N1

N3

N5

N6

N7

N8

N1

N1

N1-N2

N1-N3-N4

N1-N3-N4

N1-N3-N4-N7

N1-N3-N4-N6N1-N3

N1-N3-N4

N1-N2-N5

N2

N4N1

N3

N5

N6

N7

N8N1-N2-N5-N

8

N1-N2-N5-N

8

N1-N2-N5-N

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Route Discovery

Route Reply

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Modified DSR

Route information determined by the current networkconditions

number of hops

congestion

node energy

Other considerations

fairness

number of route requests

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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)

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Zone Radius = r Hops

Zone of Node Y

Node X

Zone of Node XNode ZZone of Node Z

Border Node

Border Node

Bordercasting

Zone Routing Protocol (ZRP)

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Location-Aided Routing (LAR)

Location information via GPS

Shortcoming (maybe not anymore 2005)

GPS availability is not yet worldwide

Position information come with deviation

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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 doesnt know a route to D Previous route from S to D is broken

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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

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LAR

source(Xs,Ys)

Request ZoneExpected Zone (Xd+R, Yd+R)

R

Destination (Xd,Yd)

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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

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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 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 timest

amp of the position information source has about destination, and Vmax is the maximum speed that anode may travel in the ad hoc network

The direction toward destination is defined by the line between source and destination and the angle

30From ECE 5970 Class

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DREAM

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Power-Aware Routing (PAR)

+

+

+

+

+

+

SRC

N1 N2

DES

T

N4N3

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OLSR - Overview

OLSR Inherits Stability of Link-state protocol

Selective Flooding

only MPRretransmit control messages:

Minimize flooding

Suitable for large and dense networks

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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 its MPR is bidirectional.

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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

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Figure 1. Diffusion of a broadcast message using multipoint relays

4 retransmission to diffuse a

message up to 2 hops

MPR(Retransmissionnode)

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Node 1 Hop Neighbors 2 Hop Neighbors MPR(s)B A,C,F,G D,E C

A

B

C

DE

F

G

Figure 2. Network example for MPR selection

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MS(A) = {B,H,I}

A

G

F HE

ID C B

MS(C) = {B,D,E} MPR(B) = {A,C}

Figure 3. MPR MPR Selector Set

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Protocol functioning Neighbor sensing

Each node periodically broadcasts its HELLO messages: Containing the information about its neighborsand 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

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Protocol functioning Neighbor sensing (cont.)

Message type Vtime Message size

Originator Address

Time To Live Hop count Message Sequence Number

Reserved Htime Willingness

Link code Reserved Link message size

Neighbor Interface Address

Neighbor interface Address

Reserved Htime Willingness

Link code Reserved Link message size

Neighbor interface address

Neighbor interface address

Table 1. Hello Message Format in OLSR

Link type Neighbor type

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Protocol functioning Neighbor sensing (cont.)

HELLO messages : ServesLink 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

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Protocol functioning Neighbor sensing

Example of neighbor tableOne-hop neighbors

MPRC

UnidirectionalG

BidirectionalB

State of LinkNeighbors id

Two-hop neighbors

CD

CE

Access thoughNeighbors id

Table 2. Example of neighbor table

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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 newneighbor )

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

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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 maintainsa Topology Tablebased on TCmessages

Routing Tablesare calculated based on Topology tables

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Protocol functioning MPR information declaration (cont.)

Destination address Destinations MPR MPR 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

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G

FE

D C B

MS(C) = {B,D,E} MPR(B) = {A,C}

Figure 4. TC message and Topology table

Send TC message

{B,D,E} build thetopology table

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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 thenew one is recorded

If the entry is the sameas in TC message, the holding time of

this entry is refreshed

If there are nocorresponding entry the new entry is

recorded

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S

B

D

M

X Y Z

P

A

Send TC message

Dest

addressDest MPR

MPR

Selector

sequence

X M 1

Y M 1

Z M 1

.. .. ..

STopology table

TC

originatorMPR selector

MPR selector

sequence

M X 2

M Y 2

M Z 2

M R 2

TC message M send to S)

R

Figure 5. Topology table update

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Protocol functioning Routing table calculation

Each node maintains a routing table to all knowndestinations in the network

After each node TC message receives, store connected pairsof

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 neighbortable or in topology table

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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

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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

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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

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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)

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References

Ad Hoc Mobile Wireless Networks Protocols and System, C-K Toh, Prentice Hall, 2002, ISBN: 0-13-007817-4 Introduction to Ad Hoc Networking, Prof. Yu-Chee Ts

eng

Optimized Link State Routing Protocolfor Ad Hoc Networks, Jacquet, p and park gi won

Ad Hoc Network, Wireless LANs, June September

2009, Asso. Prof. Anan Phonphoem, Ph.D.

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