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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
8
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
26
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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
31
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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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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(Retransmissionnode)
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OLSR Multipoint relays (cont.)
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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OLSR Multipoint relays (cont.)
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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Protocol functioning MPR information declaration (cont.)
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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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 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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Protocol functioning MPR information declaration (cont.)
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.