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Sungkyunkwan University

Copyright 2000-2016 Networking Laboratory

Networking Now

Hyunseung ChooNetworking Laboratory

Sungkyunkwan University

[email protected]://monet.skku.ac.kr

mailto:[email protected]

Networking Now 2016 Networking Laboratory 2/237

MANET / WSN

Overview page 4~

Flooding / Broadcasting page 17~

Routing: Ad Hoc Networks page 39~

Routing: Sensor Networks page 93~

Mobile Sinks page 120~

Localization page 130~

Geographic Routing page 146~

Coverage Problem page 196~

Data Aggregation and Collection page 209~

Scheduling page 214~

Developments page 227~

Contents


MANET / WSN

- Grand ICT 연구센터지원사업라이프컴패니온쉽경험을위한지능형인터랙션융합연구

- 무선포함접속방식에독립적인차세대네트워킹기술개발SDN/NFV기반의기업유무선통합네트워크를위한액세스기술독립적오픈소스컨트롤러개발

- 자율제어네트워킹및 자율관리핵심기술개발생체모방자율제어시스템및자율관리/통합플랫폼구축

- 스마트TV 2.0 소프트웨어플랫폼M2M을위한디바이스인터랙션기술개발

- 첨단인터랙션을위한기반 SW 융합기술연구인간과기기, 기기와기기간의첨단인터랙션을위한융합 SW중심의기반SW 개발


Overview


Computing Class Transition

year

log

(peop

le p

er

compu

ter)

streaming informationto/from physical world

Number CrunchingData Storage

productivityinteractive

Mainframe

Minicomputer

Workstation

PC

Laptop

PDA


MANETs & WSNs

Wireless Sensor Networks

The growth of laptops and 802.11/Wi-

Fi wireless networking have made

Mobile Ad-hoc Networks (MANETs) a

popular research topic since the mid- to

late 1990s

Based on the development of devices

and MANETs, Wireless Sensor

Networks (WSNs) are becoming a “hot”

research topic

Mobile Ad hoc Networks (MANETs)


A “mobile ad hoc network” (MANET) is an autonomous system of mobile routers

connected by wireless link--the union of which form an arbitrary graph

The routers are free to move randomly and organize themselves arbitrarily; thus,

the network’s wireless topology may change rapidly and un-predictably

MANETs

• Routing protocols

• QoS

• Medium access control

• Low power design

• Mobility management

• Security

Challenges

Evolution of Ad hoc Networks

The Early Influence of Military Applications

Ad hoc Networks and the Internet

The Internet of Things and SDN-based Ad hoc

networking


What is WSNs?

Network of thousands of extremely small, low power devices

Network of equipments which are programmable computing, multiple

sensing, communication capability

Motivation: robustness, scalability, energy efficiency

*Ref: Wireless Sensor Network Survey, Computer Networks Journal, I. Akilydiz , et al.


Preliminaries (1/2)

*Ref: Wireless Sensor Network Survey, Computer Networks Journal, I. Akilydiz , et al.

Transducer: converts a physical phenomenon into electrical signals

Sensor Node:

A device capable of physical sensing of environmental phenomena or events,

processing sensed data, and reporting the measurements


Actuator: action command generator based on data

Receives data from sensors and process it

Generates an action command based on the result

Action command is converted to an analog Signal

Preliminaries (2/2)

*Ref: Wireless Sensor Network Survey, Computer Networks Journal, I. Akilydiz, et al.

Sensor node Integrated with actuator


General Purpose Sensors

Single-purpose network is the typical assumption, but not

the future

Sensors for evolving applications

Sensors that can adapt to changing objectives

More memory and CPU will allow more complex applications

Network Independent

Hardware interface

Network SpecificNetwork


Sensor Hardware Platform

MicaZ 2004250kbps

2.4GHz ISM802.15.4/Zigbee


Sensor Network Characteristics Task (application)-specific information gathering platform

High node density and highly limited resources such as battery, data processing

capability, memory, and communication bandwidth

Frequent topology changes due to node mobility and node failure (energy

depletion)

Collaborative task-fulfillment to gather specific information to help

users/applications to make more meaningful decisions

Broadcasting based Communication for Data Dissemination

M-to-one or one-to-M communications, push (interest is sensed, by sensors) and

pull (what has been sensed so far, by the user) concept

Immediate reporting (sensed results) on critical changes of monitoring target

Sensor nodes do have either global IDs like IP addresses or network-specific ID

Deployment is ad hoc in general

Embedded in and adapting to physical environment

In-network processing, not end-to-end, as in traditional TCP/IP applications


Sensor Network Applications

Civil structural monitoring

Habitat/ecosystem monitoring

Agricultural maintenance networks

Environmental monitoring

Traffic/Vehicle Monitoring

Military security/alerting networks

Chemical Detection

Target Detection/Tracking

Smart homes

Human Health Monitoring

Robotic sensor networks

Circulatory Net


Applications (cont’d)


Flooding / Broadcasting


Flooding Schemes

Flooding is an indispensable

operation for providing control or

routing functionalities

However, naive broadcasting

causes severe redundant

transmissions, congestion of the

wireless media and collisions in

networks

We need efficient flooding schemes Flooding and Routing


Efficient Flooding Scheme using 1-Hop

Information*

Assumptions:

All nodes in the network have the same transmission range R

Each node has a unique ID

The location information of each node can be obtained via GPS or

some distributed localization methods

A node needs to know the information of its direct neighbors,

including their IDs and their geographic locations.

[*] H. Liu, X. Jia, P. Wan, X. Liu and F. F. Yao, “A Distributed and Efficient Flooding Scheme Using 1-Hop Information in

Mobile Ad Hoc Networks,” IEEE Transactions on Parallel and Distributed System, vol. 18, no. 5, 2007



Information

Basic idea:

The source node computes a subset of its neighbors as forwarding

nodes and attaches the list to the message

Then, the source transmits the message

Every node receives the message checks if itself is in the

forwarding list:

If yes, it computes the next hop forwarding nodes and

transmits the message as the same way as the source

Otherwise, it drops the message



Information: Computing Forwarding Set

Only having 1-hop neighbor information, to achieve 100%

deliverability, the coverage area of s’s forwarding set F(s) must cover

the entire neighbor’s coverage area of s

vv

uuss ww

Task

Every node in F(s) must contribute to

the boundary of s’s neighbor

coverage area

For example, s is the flooding source

and s’s neighbor set N(s) = { u, v, w }

In this case, F(s) = { s, v, u } because

the coverage area of w is covered by

the coverage areas of s, v, and u

Coverage

Area of w

Coverage

Area of u

Coverage

Area of s

Coverage

Area of v



Information: Forwarding Node Optimization

When node u receives the message from s, the computing of F(u) can

be further optimized based on the information of F(s) = {s,u,v}

vv

uuss

Consider node u with the initial

forwarding set F(u) = {u,1,2,3,4,5,6}

Since nodes 1 and 2 are already

covered by s, u can remove them from

the forwarding set; F(u) = {u,3,4,5,6}

Because 3 is covered by v, u can safely

remove node 3 from its forwarding set.

Finally, F(u) = {u,4,5,6} Coverage

Area of u

Coverage

Area of s

Coverage

Area of v


Efficient Flooding Scheme Exploiting 2-Hop

Backward Information*: Forwarding Set Optimization (1/3)

Rule 1: The retransmission node removes from its forwarding set the nodes that

have already been covered by its sender node

Rule 1: The retransmission node removes from its forwarding set the nodes that

have already been covered by its sender node

After applying Rule 1; Fopt(4) = {6, 8}: remove node 7 because it has received the

flooding message from sender 3

After having the Forwarding Set,

intermediate nodes will further

optimize the Forwarding Set by

applying those rules. For

example, considering node 4

with the initial Forwarding Set,

F(4) = {3, 6, 7, 8}2

5

4

Rule #1

area

3

6

87

0source

1

Neighbors’ coverage

area of node 0

(node 4’s 2-hop

backward node)

Nodes in the

forwarding set

Retransmission

nodes

Duty abandoning

nodes

Nodes are not in

forwarding sets

11

10

9

[*] T. D. Le and H. Choo, “Towards an Efficient Flooding Scheme Exploiting 2-Hop Backward Information in MANETs,” IEICE

Transaction on Communications, vol. E92-B, no. 4, pp. 1199-1209, 2009



Backward Information: Forwarding Set Optimization (2/3)

Rule 2: The retransmission node

that is closer to the sender removes

from its forwarding set the nodes

that are in the overlapping zones

Rule 2: The retransmission node

that is closer to the sender removes

from its forwarding set the nodes

that are in the overlapping zones

After applying Rule 2; Fopt(4) = {6}: remove node 8 because it is the neighbor of node 5

which is farther from sender node 3 than node 4

After applying Rule 1; Fopt(4) = {6, 8}

2

5

43

6

87

0source

1


area of node 0

(node 4’s 2-hop

backward node)

Nodes in the

forwarding set

Retransmission

nodes

Duty abandoning

nodes

Nodes are not in

forwarding sets

11

10

9

Rule #2

area



Backward Information: Forwarding Set Optimization (3/3)

Rule 3: Based on the forwarding set

information of its 2-hop backward

node, the retransmission node

removes from the forwarding set the

nodes that are in the neighbors’

coverage area of the 2-hop

backward node

Rule 3: Based on the forwarding set

information of its 2-hop backward

node, the retransmission node

removes from the forwarding set the

nodes that are in the neighbors’

coverage area of the 2-hop

backward node

After applying Rule 2; Fopt(4) = {6}

After applying Rule 3; Fopt(4) = {}: remove node 6 because it is 1-hop neighbor of node 2

or 2-hop neighbor of node 0

Node 4 does not need to rebroadcast flooding messages

2

5

43

6

87

0source

1


area of node 0

(node 4’s 2-hop

backward node)

Nodes in the

forwarding set

Retransmission

nodes

Duty abandoning

nodes

Nodes are not in

forwarding sets

11

10

9

Rule #3

area


Time To Live Sequence Based Expanding Rin

g Search (ERS)* (1/2)

Time To Live Sequence based Expanding Ring Search (ERS)

algorithm is a technique that can avoid network wide broadcasting by

searching a larger area around the source of broadcast

The source node send a query with a small

Time To Live (TTL) value (usually 1). Each

time the query is relayed by an intermediate

node, the TTL value is decreased by 1

If the TTL is greater than 0, the query will be

forwarded

Destination

S

D

RREQ: TTL = 1S

D

Source Node have route

to destination

[*] J. Hassan and S. Jha, “Optimising Expanding Ring Search for MultiHop Wireless Networks,” IEEE Global Telecommunications

Conference, Dallas, TX, 2004


If there is no reply within the time out period, the

source node increases the radius of the searching

ring by increasing the TTL

S

D

RREQ: TTL = 3

The searching process continues until

the information needed is found or the

TTL value reaches a threshold T

If the TTL reaches the threshold T, the

source starts a broadcast to the entire

network

S

D

Source

Destination

Node have route to

destination

Node in the 1st ring

Time To Live Sequence Based Expanding Rin

g Search (ERS) (2/2)


Energy Efficient Expanding Ring Search*

Motivation:

In pure flooding, if node receives a duplicate packet, it will drop the duplicate

packets

The duplicate packets can store neighbors’ information which can be used to

get the network topology for reducing the overhead of the next pure flooding

Approach:

When relaying a message, the node adds the predecessor address

(previous node address) into the message

Based on the predecessor address, nodes can know local network topology

A CBD E

After receiving messages from B and C, A knows

the predecessor of B is D and the predecessor of

C is E

[*] N. D. Pham and H. Choo, “Energy Efficient Expanding Ring Search for Route Discovery in MANETs,” In Proceeding of

IEEE International Conference on Communications, pp. 3002-3008, 2008


Energy Efficient Expanding Ring Search: Collecting local topology information (1/4)

O A

B

C

D

Relay: false

predAddr: A

Relay: false

predAddr: A

Relay: false

predAddr:

Relay: false

predAddr: A

Relay: false

predAddr:

Every node has a variable “Relay” which initial value is “False”

Node A want to send a message to an entire network, it broadcasts the

message to its neighbors (O,B,C)

Node A becomes the predecessor of node O,B, and C



Assume B firstly relays the message received from A.

D sets its “Predecessor Address” to B due to its first time receiving

A receives a duplicate message, and the predecessor address in the message

is A A sets “relay” to true

C receives a duplicate message, but the predecessor address in the message

is different from C C drops the message

O A

B

C

D

Relay: false

predAddr: A

Relay: false

predAddr: A

Relay: false

predAddr: B

Relay: false

predAddr: A

Relay: true

predAddr:



Likewise, O and C relay the message received from A

Each node receiving the messages from O and C completes the same

process as done in A and C above

O A

B

C

D

Relay: false

predAddr: A

Relay: false

predAddr: A

Relay: false

predAddr: B

Relay: false

predAddr: A

Relay: true

predAddr:



Finally, D relays the message received from B

B overhears the message, obtains the predecessor address and

compares to its address. They are the same B sets its “relay” to true

O A

B

C

D

Relay: false

predAddr: A

Relay: true

predAddr: A

Relay: false

predAddr: B

Relay: false

predAddr: A

Relay: true

predAddr:


Energy Efficient Expanding Ring Search: Reducing the overhead of pure flooding

After a pure flooding of A, assume that O wants to send a message to

the entire network

Only the nodes that have the variable “relay” set to true can relay the

message from O

O A

B

C

D

Relay: false

predAddr: A

Relay: true

predAddr: A

Relay: false

predAddr: B

Relay: false

predAddr: A

Relay: true

predAddr:


Duty Cycle Aware Broadcast* (1/5)

In WSNs, the lifetime of a sensor node is limited due to battery capacity

duty cycle (Sleep/Awake scheduling) is an effective strategy to save

energy

In duty cycle WSNs, due to intermittent connections between sensors,

a node needs to broadcast the message several times to cover all its

direct neighbors

sleepactive

S

B

C

D

B

C

D

Network topology

t2t0 t4 t6 t8

Working schedule

S has to broadcast 3 times

at t3, t5, t7

[*] F.Wang, J.Liu, “Duty-Cycle-Aware Broadcast in Wireless Sensor Networks,” INFOCOM, 2009


Duty Cycle Aware Broadcast (2/5)

For broadcasting in duty cycle WSNs, there is a trade off between the

number of broadcast messages and delay time

Based on the working schedule, the authors used the Time Coverage

graph to find a broadcast schedule that balances the number of

broadcast messages and delay time

We call a node is covered if it has received the message. The

coverage set S at time slot t contains all the nodes which have

received the message at t



Time-Coverage Graph

…

time

CovSet

…

…

…

… … …

…

… … … …

{s}

t0

{s}t0+1

{s}t0+2

{s}t0+j

{s,n1}

t0

{s,n1}

t0+1

{s,n1}

t0+2

{s,n1}

t0+j

{.,s,.}

t0

{.,s,.}

t0+1

{.,s,.}

t0+2

{.,s,.}

t0+j

{1,..,s,

..,n}

t0

{1,..,s,

..,n}

t0+1

{1,..,s,

..,n}

t0+2

{1,..,s,

..,n}

t0+j

Time edge

Forwarding edge

There are many paths toward

the last row



There are 2 types of edges in Time-Coverage graph:

Time edge: all nodes in the coverage set wait until the next time

slot

Forward edge: some nodes in the coverage set S broadcast the

message and leads to another coverage set S’.

a) Time edge b) Forward edge

w

w

w: weight of the edge

<S, t> <S, t +1>

<S, t >

<S’ ,t+1>


Practice Problems

Give some important characteristics of the wireless sensor

networks

What is the key idea in using 1-hop neighbor information to

achieve efficient flooding?


Routing

in Wireless Ad Hoc Networks


Reactive Routing Protocols: Introduction (1/2)

Also called "on-demand" routing protocols

Routing paths are searched only when needed

A route discovery operation invokes a route-determination

procedure

This procedure terminates either when a route has been

found or no route available after examination for all route

permutations

In a mobile ad hoc network, active routes may be

disconnected due to node mobility

Route maintenance is an important operation of reactive routing

protocols


Reactive Routing Protocols: Introduction (2/2)

Pros and Cons:

Less control overhead compared to proactive routing protocols

Source nodes may suffer from long delays for route searching

before they can forward data packets

Reactive routing schemes/protocols

Dynamic Source Routing (DSR)

Ad Hoc On-Demand Distance Vector Routing (AODV)

Temporally-Ordered Routing Algorithm (TORA)


Reactive Routing Protocols: References

[1] Dynamic Source Routing (DSR),

http://tools.ietf.org/html/rfc4728

[2] Ad Hoc On-Demand Distance Vector Routing (AODV),

https://tools.ietf.org/html/rfc3561

[3] V. D. Park and M. S. Corson, "A highly adaptive distributed

routing algorithm for mobile wireless networks," IEEE

INFOCOM, vol. 3, pp.1405-1413, 1997. (TORA)




Dynamic Source Routing (DSR)*

When node S wants to send a packet to node D, but does

not know a route to D, node S initiates a route discovery

Source node S floods Route Request (RREQ)

Each node appends its own identifier when forwarding

RREQ

[*] Dynamic Source Routing (DSR), http://tools.ietf.org/html/rfc4728



S

Dynamic Source Routing (DSR) : Route Discovery (1/2)

B

A

E

F

H

J

D

C

G

I

K

M

N

L

[S][S,E]

[S,E,F]

[S,E,F,J]

Represents transmission of RREQ

[X,Y] Represents list of identifiers appended to RREQ


Dynamic Source Routing (DSR) : Route Discovery (2/2)

Destination D on receiving the first RREQ, sends a Route

Reply (RREP)

RREP is sent on a route obtained by reversing the route

appended to received RREQ

RREP includes the route from S to D on which RREQ was

received by node D


S

Dynamic Source Routing (DSR) : Route Reply (1/2)

Represents RREP control message

B

A

E

F

H

J

D

C

G

I

K

M

N

L

RREP [S,E,F,J,D]


Dynamic Source Routing (DSR) : Route Reply (2/2)

Route Reply can be sent by reversing the route in Route

Request (RREQ) only if links are guaranteed to be bi-

directional

► To ensure this, RREQ should be forwarded only if it is received on

a bi-directional link

If unidirectional (asymmetric) links are allowed, then RREP

may need a route discovery for S from node D

► Unless node D already knows a route to node S

► If a route discovery is initiated by D for a route to S, then the Route

Reply is piggybacked on the Route Request from D

If IEEE 802.11 MAC is used to send data, then links have

to be bi-directional (since Ack is used)


Dynamic Source Routing (DSR) : Sending data

Node S on receiving RREP, caches the route included in

the RREP

When node S sends a data packet to D, the entire route is

included in the packet header

► Hence the name is source routing

Intermediate nodes use the source route included in a

packet to determine to whom a packet should be

forwarded


Ad Hoc On-Demand Distance Vector

Routing (AODV)*

DSR includes source routes in packet headers

Resulting large headers can sometimes degrade performance► Particularly when data contents of a packet are small

AODV attempts to improve DSR by maintaining routing tables at the

nodes, so that data packets do not have to contain routes

AODV retains the desirable feature of DSR that routes are maintained

only between nodes which need to communicate

[*] Ad Hoc On-Demand Distance Vector Routing (AODV), https://tools.ietf.org/html/rfc3561




Routing (AODV)

Route Requests (RREQ) are forwarded in a manner similar to DSR

When a node re-broadcasts a Route Request, it sets up a reverse path

pointing towards the source► AODV assumes symmetric (bi-directional) links

When the intended destination receives a Route Request, it replies by

sending a Route Reply

Route Reply travels along the reverse path set-up when Route

Request is forwarded



Routing (AODV): Reverse Path Setup

S

B

A

E

F

H

J

D

C

G

I

K

M

N

L

Represents transmission of RREQ

Represents links on Reverse Path



Routing (AODV): Route Reply (1/2)

S

B

A

E

F

H

J

D

C

G

I

K

M

N

L

Represents links on path taken by RREP



Routing (AODV): Route Reply (2/2)

An intermediate node (not the destination) may also send a Route

Reply (RREP) provided that it knows a more recent path than the one

previously known to sender S

To determine whether the path known to an intermediate node is more

recent, destination sequence numbers are used

The likelihood that an intermediate node will send a Route Reply when

using AODV not as high as DSR► A new Route Request by node S for a destination is assigned a higher destination sequence

number. An intermediate node which knows a route, but with a smaller sequence number,

cannot send Route Reply



Routing (AODV): Forward Path Setup

S

B

A

E

F

H

J

D

C

G

I

K

M

N

L

Forward links are setup when RREP travels along

the reverse path

Represents a link on the forward path


Partial Reversal Method (1/6)

A FB

C E G

D

Maintain a directed acyclic

graph (DAG) for each

destination, with the destination

being the only sink

This DAG is for destination

node D

Links are bi-directional

But algorithm imposes

logical directions on them



Link (G,D) broke

A FB

C E G

D

Node G has no outgoing links

How to update routing

tables of nodes when links

are broken?



A FB

C E G

D

Now nodes E and F have no outgoing links

Represents a

link that was

reversed recently

Represents a

node that has

reversed links



A FB

C E G

D

Represents a

link that was

reversed recently



A FB

C E G

D

Now node A has no outgoing links

Represents a

link that was

reversed recently



A FB

C E G

D

Now all nodes (except destination D) have outgoing links

Thus, DAG has been restored with only the destination as a sink

Represents a

link that was

reversed recently


Temporally-Ordered Routing

Algorithm (TORA) (1/9)

If network is partitioned, link reversals continue

indefinitely

TORA modifies the partial link reversal method to be

able to detect partitions

When a partition is detected, all nodes in the partition

are informed, and link reversals in that partition cease

[*] V. D. Park and M. S. Corson, "A highly adaptive distributed routing algorithm for mobile wireless networks," IEEE INFOCOM,

vol. 3, pp.1405-1413, 1997.


A

B

E

D

F

C

DAG for

destination D




A

B

E

D

F

C

TORA uses a

modified partial

reversal method

Node A has no outgoing links




A

B

E

D

F

C

TORA uses a

modified partial

reversal method

Node B has no outgoing links




A

B

E

D

F

C

Node B has no outgoing links




A

B

E

D

F

C

Node C has no outgoing links -- all its neighbors have

reversed links previously.




A

B

E

D

F

C




A

B

E

D

F

C

Node A has received the reflection from all its neighbors.

Node A determines that it is partitioned from destination D.

Node B propagates

the reflection to node A




A

B

E

D

F

COn detecting a partition,

node A sends a clear (CLR)

message that purges all

directed links in that

partition




Proactive Routing Protocols : Introduction (1/2)

Routes are calculated and stored in routing table in each

node before a node needs to find a path to destination

Routing information in all nodes is updated every time

There are two ways of updating the routing tables:

Event-driven: update messages are sent only when the network

topology changes

Cycle: update messages are sent throughout the network

periodically


Proactive Routing Protocols : Introduction (2/2)

Advantages

Slow latency

Suitable for real-time traffic

Disadvantages

Bandwidth may get wasted due to periodic updates

Slow reaction on restructuring and failures

Proactive routing schemes

Wireless Routing Protocol (WRP)

Distance Routing Effect Algorithm for Mobility (DREAM)

Destination Sequence Distance Vector (DSDV)

Fisheye State Routing (FSR)


Proactive Routing Protocols: References

[1] S. Murthy, J. J. Garcia-Luna-Aceves, "An efficient routing protocol

for wireless networks," Mobile Networks and Applications,

vol. 1(2), pp. 183–197, 1996. (WRP)

[2] S. Basagni, I. Chlamtac, V. Syrotiuk and B. WoodWard, “A

Distance Routing Effect Algorithm for Mobility (DREAM),”

MOBICOM, 1998.

[3] C. E. Perkins and P. Bhagwat, “Highly dynamic Destination-

Sequenced Distance-Vector Routing (DSDV) for mobile

computers,” SIGCOMM, 1994.

[4] G. Pei, M. Gerla and T.-W. Chen, “Fisheye State Routing in

Mobile Ad Hoc Networks,” ICDCS Workshops, 2000.


Wireless Routing Protocol*

Problem: Wireless Routing Protocol (WRP) is a proactive

unicast routing protocol for mobile ad-hoc networks

(MANET)

Goal: WRP is a table-based protocol with the goal of

maintaining routing information among all nodes in the

network

Motivation: WRP used an enhanced version of the

distance-vector routing protocol, which used the Bellman-

Ford algorithm to calculate paths

[*] S. Murthy, J. J. Garcia-Luna-Aceves, "An efficient routing protocol for wireless networks," Mobile

Networks and Applications, vol. 1(2), pp. 183–197, 1996.


Wireless Routing Protocol : Operation of WRP (1/4)

1

1

1

10

10

5(2,K)

(2,K)

(1,K)

(0,J)

K

I

J

B

Source node

Destination node

Normal node

Example:

Given the network of 4 nodes, node I is

the source, and node J is the destination

Each communication link is assigned

a cost (link-cost)

The arrow links show the shortest path

to destination J from nodes I, B, and K

The label in parentheses (distance

table) gives the distance and the

penultimate node (the node next to

destination) to destination J


1

1

10

10

5(2,K)

(2,K)

(infinity, -)

(0,J)

K

I

J

B

Source node

Destination node

Normal node

Situation: Link KJ fails

Operation:

The distance table of node J does not

change, while the distance table of node

K is changed to (infinity, -)

Node K sends the update messages

to its neighbors (nodes B and I) to report

the infinity distance to destination J

Update message



1

1

10

10

5(10,B)

(10,I)

(infinity, -)

(0,J)

K

I

J

B

Source node

Destination node

Normal node

Operation: (cont.)

Because nodes B and I know that node

K is the penultimate node to destination

J. They update their distance tables

Node B processes node K’s update and

select link BJ to destination J. Then, it

sends update message to its neighbors

When I gets node K’s update message, it

updates its distance table through node

K and checks for the possible path to

destination J through any other

neighboring nodes. This results in the

selection of link IJ to destination J. Then,

it sends update message to its neighborsUpdate message



1

1

10

10

5(10,B)

(10,I)

(11, B)

(0,J)

K

I

J

B

Source node

Destination node

Normal node

Operation: (cont.)

Node K processes update messages

from nodes B and I and update its

distance table to (11, B). Then, it sends

update messages to its neighbors

The update messages from node K do

not affect the path information of nodes

B and I

Update message



Advantages

The novelty of WRP is in the way in which it achieves loop freedom

WRP involves fewer table updates than DSDV

Disadvantages

The complexity of maintenance of multiple tables demands a larger

memory, and greater processing power from nodes

Due to the control overhead, the protocol is not suitable for highly

dynamic and also for a large ad hoc wireless network

Wireless Routing Protocol : Properties


Distance Routing Effect Algorithm for

Mobility (DREAM)* (1/4)

Uses location and speed information of mobile nodes for

data packet routing

DREAM uses flooding of data packets as the routing

mechanism

► DREAM uses location information to limit the flood of data packets

to a small region

[*] S. Basagni, I. Chlamtac, V. Syrotiuk and B. WoodWard, “A Distance Routing Effect Algorithm for Mobility (DREAM),”

MOBICOM, 1998.


S

D

Expected zone

A

Node A, on receiving the

data packet, forwards it to

its neighbors within the

cone rooted at node A

S sends data packet to all

neighbors in the cone rooted

at node S


Mobility (DREAM) (2/4)


X

Y

r

X = last known location of node

D, at time t0

Y = location of node D at current

time t1, unknown to node S

r = (t1 - t0) * estimate of D’s speed

Expected Zone




Nodes periodically broadcast their physical location

Nearby nodes are updated more frequently, far away

nodes less frequently

Distance effect: Far away nodes seem to move at a lower

angular speed as compared to nearby nodes

Location update’s time-to-live field used to control how far

the information is propagated




Destination Sequence Distance Vector

(DSDV)* (1/5)

DSDV is based on the traditional Bellman-Ford algorithm

Each node maintains routing information for all known

destinations

Routing information must be updated periodically

Traffic overhead occurs even if there is no change in

network topology

[*] C. E. Perkins and P. Bhagwat, “Highly dynamic Destination-Sequenced Distance-Vector Routing (DSDV) for mobile computers,”

SIGCOMM, vol. 24, no.4, pp. 234–244, 1994.


Maintains routes which are never used

Keeps the simplicity of Distance Vector

Guarantees Loop Freeness by using Destination Sequence

Number

Allows fast reaction to topology changes

Making immediate route advertisement on significant changes in

routing table

But, waiting with advertising of unstable routes (damping

fluctuations)


(DSDV) (2/5)


Table entries

Metric: delay, number of hops, signal strength, etc.

Sequence number: originated from destination; ensures

loop freeness

Install Time: when entry was made (used to delete stale entries

from table)

Destination Next Metric Seq. Nr Install Time

A A 0 A-550 001000

B B 1 B-102 001200

C B 3 C-588 001200

D B 4 D-312 001200

Table Entries


(DSDV) (3/5)


Route Advertisements

Each node advertises its own routing information to its neighbors

Destination Address

Metric = Number of Hops to Destination

Destination Sequence Number

Rules for setting sequence number information are provided

On each advertisement, each node increases its own destination

sequence number (use only even numbers)

If a node is no longer reachable (timeout), its sequence number is

increased by 1 (odd sequence number) and the metric is set to infinite


(DSDV) (4/5)


Route Selection

Update information is compared to the current routing table

Selecting routes with higher destination sequence number (This ensure

s to use newest information from destination always)

Selecting routes with better metric when sequence numbers are equal


(DSDV) (5/5)


Fisheye State Routing (FSR)* (1/5)

FSR is similar to link state (LS) routing in that each node

maintains a view of the network topology with a cost for

each link

In LS routing, link state packets are flooded into the network

whenever a node detects a topology change

In FSR, nodes maintain a topology table (TT) based on the

up-to-date information received from neighboring nodes

and periodically exchange it with their local neighbors

[*] G. Pei, M. Gerla and T.-W. Chen, “Fisheye State Routing in Mobile Ad Hoc Networks,” ICDCS Workshops, 2000.


For large networks, in order to reduce the size of the routing

update messages the FSR technique uses different

exchange periods for different entries in the routing table

The network is divided in different scopes

Fisheye State Routing (FSR) (2/5)


“Fish-Eye”

Captures pixels near the focal point with more details

The detail decreases as the distance from the focal point increases

Maintains accurate information in immediate neighbors



Central node (red dot) has the most

accurate information about nodes in

white area and so on.

Parameters: Scope level/radius size



0

5

1

2

4

3

0:{1}

1:{0,2,3}

2:{5,1,4}

3:{1,4}

4:{5,2,3}

5:{2,4}

1

0

1

1

2

2

TT HOP

0:{1}

1:{0,2,3}

2:{5,1,4}

3:{1,4}

4:{5,2,3}

5:{2,4}

2

1

2

0

1

2

TT HOP

0:{1}

1:{0,2,3}

2:{5,1,4}

3:{1,4}

4:{5,2,3}

5:{2,4}

2

2

1

1

0

1

TT HOPEntries in black

are exchanged

more frequently

Message Reduction in FSR


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