o c t o p u s scalable routing protocol for wireless ad hoc networks

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O C T O P U SO C T O P U S

Scalable Routing ProtocolScalable Routing Protocol For Wireless Ad Hoc For Wireless Ad Hoc

NetworksNetworks

- Lily Itkin - Evgeny Gurevich - Inna Vaisband -- Lily Itkin - Evgeny Gurevich - Inna Vaisband -

Lab Chief Engineer: Dr. Ilana DavidLab Chief Engineer: Dr. Ilana DavidInstructor: Roie MelamedInstructor: Roie Melamed

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Proactive protocolsProactive protocols continuously updates the “reachability” continuously updates the “reachability”

information at all the network nodesinformation at all the network nodes when a route is requested, it is immediately when a route is requested, it is immediately

availableavailable Problem:Problem: waste wireless resourceswaste wireless resources for handling frequent for handling frequent

updates, especially for large, highly mobile networksupdates, especially for large, highly mobile networks Reactive protocolsReactive protocols

discover routes discover routes onlyonly upon demand upon demand involve some sort of “global search” which can involve some sort of “global search” which can

causes a significant delaycauses a significant delay Problem:Problem: very slow, high overhead for each requestvery slow, high overhead for each request

Octopus - Hybrid protocol - Octopus - Hybrid protocol - combines the combines the advantages of both approachesadvantages of both approaches Cheap maintenance of the proactive part (Core Cheap maintenance of the proactive part (Core

module)module) Low-overhead location time - reactive part (FL Low-overhead location time - reactive part (FL

module)module) Simple protocolSimple protocol

Location Based Routing Location Based Routing ProtocolsProtocols

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Octopus’ GridOctopus’ Grid The space is divided to horizontal and vertical The space is divided to horizontal and vertical

stripsstripsThe division is related to a (0,0) point and not The division is related to a (0,0) point and not affected by the nodes’ locationsaffected by the nodes’ locations

100 200 300 400 500 600

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Each node knows its vertical and horizontal Each node knows its vertical and horizontal stripsstrips

a

i

f

ec

g h

db j

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Core Module: The Neighbor Core Module: The Neighbor ListList

(proactive part)(proactive part) Each node in a range of 250m receives this Each node in a range of 250m receives this

message and updates its one-hop neighbor list message and updates its one-hop neighbor list accordingly.accordingly.

a

i

100 200 300 400 500 600

100

200

300

400

f

ec

g h

db j

updates the list

updates the list

updates the list

updates the list

updates the list

updates the list

updates the list

updates the list

updatesthe list

updatesthe list

Every timeout, each node broadcasts its ID and Every timeout, each node broadcasts its ID and location. location.

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Core Module: The Strips DBCore Module: The Strips DB(proactive part)(proactive part)

a

i

f

ec

g h

db j

100 200 300 400 500 600

100

200

300

400

At the end, the east table of node a is {b, c, d, e, At the end, the east table of node a is {b, c, d, e, j}.j}.

j,e,dj,e,d,cj,e,d,c,bj,e,d,c,b,a

End Node j initiates the update of its strip.End Node j initiates the update of its strip.

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FL Module: Locating the FL Module: Locating the TargetTarget

(reactive part)(reactive part) Example: Node b wants to transmit data to node Example: Node b wants to transmit data to node

h, whose location node b doesn’t knowh, whose location node b doesn’t know

a

f

ec

g h

db j

100 200 300 400 500 600

100

200

300

400

h?

h?

h!h!

start communicating

source

access target

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Project WorkflowProject Workflow

Analyzing resultsAnalyzing results•building relevant building relevant tables/graphstables/graphs•extracting bottle-neck extracting bottle-neck parametersparameters

Start PointStart PointImplementatioImplementation of the basic n of the basic algorithmalgorithm

(Project I)(Project I)

SimulationsSimulations•writing scriptswriting scripts•executing scriptsexecuting scripts

Code UpdatesCode Updates•designdesign•implementationimplementation•testingtesting

Finding SolutionFinding Solution•functionality functionality updates/additionsupdates/additions•design optimizationsdesign optimizations•system/algorithm system/algorithm parametersparameters

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Functionality Functionality Updates/Additions MotivationUpdates/Additions Motivation

Low success rates (on large grids):Low success rates (on large grids): entries found by Find Location module (found entries found by Find Location module (found

~ 85%)~ 85%) reply queries returned to the source node reply queries returned to the source node

(replied ~ 80%)(replied ~ 80%) targets reached from source (received ~ 65%)targets reached from source (received ~ 65%)

Functionality Functionality Updates/Additions MotivationUpdates/Additions Motivation

Low success rates (on large grids):Low success rates (on large grids): entries found by Find Location module (found entries found by Find Location module (found

~ 85%)~ 85%) reply queries returned to the source node reply queries returned to the source node

(replied ~ 80%)(replied ~ 80%) targets reached from source (received ~ 65%)targets reached from source (received ~ 65%)

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Functionality Updates/Additions Functionality Updates/Additions - contd- contd

Sending directionsSending directions [1 direction] x [4 sendings] (default) [1 direction] x [4 sendings] (default)

Four directions (North, South, West, East) are being Four directions (North, South, West, East) are being scanned one after another - one direction at a timescanned one after another - one direction at a time

[2 directions] x [2 sendings] (optimization)[2 directions] x [2 sendings] (optimization)Four directions are being scanned in pairs (North + Four directions are being scanned in pairs (North + South, West + East)South, West + East)

[4 directions] x [1 sending] (optimization) [4 directions] x [1 sending] (optimization) Four directions (North, South, West, East) are being Four directions (North, South, West, East) are being scanned simultaneouslyscanned simultaneously

[2 directions] x [4 sendings] (optimization) [2 directions] x [4 sendings] (optimization) Eight directions are being scanned in pairs (North + Eight directions are being scanned in pairs (North + South, North-East + South-West, West + East, South-South, North-East + South-West, West + East, South-East + North-West)East + North-West)

[4 directions] x [2 sendings] (optimization) [4 directions] x [2 sendings] (optimization) Eight directions are being scanned by quartets (North Eight directions are being scanned by quartets (North + South + West + East, North-East + South-West + + South + West + East, North-East + South-West + South-East + North-West)South-East + North-West)

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ConsiderationsConsiderations Scanning less directions each time (e.g. 1 x 4, 1 x Scanning less directions each time (e.g. 1 x 4, 1 x

8)8) increases the average search timeincreases the average search time decreases the found success rate, because of the decreases the found success rate, because of the

chance that the searched chance that the searched mobile mobile node will move to the node will move to the area that is not in the currently searched directionarea that is not in the currently searched direction

Scanning more directories each time (e.g. 4 x 1, Scanning more directories each time (e.g. 4 x 1, 8 x 1)8 x 1)

overhead in resources overhead in resources high success rateshigh success rates

ConclusionConclusion The total number of sending directions and The total number of sending directions and

number of directions sent simultaneously should number of directions sent simultaneously should be determined according to user’s request and be determined according to user’s request and resourcesresources

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Reply routing modesReply routing modesAs soon as the searched node is located, the source As soon as the searched node is located, the source should be informed. This can be done in 2 ways:should be informed. This can be done in 2 ways:

by GF algorithm (default)by GF algorithm (default) by FL_REPLY algorithm (optimization)by FL_REPLY algorithm (optimization)

ConsiderationsConsiderations Default: the natural way to implement the reply to Default: the natural way to implement the reply to

source is via Geographic Forwarding, because the source is via Geographic Forwarding, because the location of the source is known in the moment of location of the source is known in the moment of the replythe reply

Problem: the accessibility of the access node from Problem: the accessibility of the access node from the source via the source via FLFL ensures the accessibility of the ensures the accessibility of the source from the access node via source from the access node via FL FL (in static (in static mode), but does not necessary means the source mode), but does not necessary means the source will be reached from the access node using will be reached from the access node using GFGF

ConclusionsConclusions The empiric results determined that there is no The empiric results determined that there is no

significant difference between the methods, which significant difference between the methods, which means that the problem appears only in very means that the problem appears only in very specific configurationsspecific configurations

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Functionality Functionality Updates/Additions - contdUpdates/Additions - contd

100 200 300 400 500 600

100

200

300

400

a

f e

cd

bFL

FL

FL

GF

Example: Example: Node a (source) wants to send data to node e Node a (source) wants to send data to node e

(target)(target) Node e (target) located by node d (access) via Node e (target) located by node d (access) via

FLFL The reply from node d (access) to node a The reply from node d (access) to node a

(source) via GF fails(source) via GF fails

source access

target

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Establishing connections modesEstablishing connections modes100 200 300 400

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300


a

g h

source

acce

ss

target

initiates communicating

a

g h

acce

ss

target

initiates communicating

source

source – access – targetsource – access – target(without reply)(without reply)request is sent directly request is sent directly from the access node to from the access node to the target node, which the target node, which initiates communication initiates communication with the sourcewith the source

source – access – source – source – access – source – target target (with reply) (with reply) the access node replies to the access node replies to the source node, which the source node, which initiates communication initiates communication with the targetwith the target

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ConclusionConclusion The empiric results determined that the rate of the The empiric results determined that the rate of the

received packets without reply is significantly higher than received packets without reply is significantly higher than the rate of the received packets with replythe rate of the received packets with reply

F O U N D A N D R E C E I V E D S U C C E S S R A T E SW I T H / W I T H O U T R E P L Y

70

80

90

100

1.0 1.5 2.0 2.5

grid space - side length [km]

succ

ess

ra

te [%

] found

received - without reply

received - with reply

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Absolute/Estimated LocationAbsolute/Estimated LocationThere are several options of treating the location to which There are several options of treating the location to which data should be sent, considering the mobility of the system data should be sent, considering the mobility of the system nodes:nodes: The specified location is the most reliable, although was The specified location is the most reliable, although was

supplied some time ago. Data is sent to the specified supplied some time ago. Data is sent to the specified location (default)location (default)

The specified location is not reliable enough. An The specified location is not reliable enough. An estimated location is calculated based on specified estimated location is calculated based on specified location, target’s velocity (a vector) and time since the location, target’s velocity (a vector) and time since the location was supplied. Data is sent to the estimated location was supplied. Data is sent to the estimated location (optimization)location (optimization)

Basic assumptions:Basic assumptions: The velocity of each node is constant during all time of the The velocity of each node is constant during all time of the

simulation.simulation. A node changes direction only when it reaches the A node changes direction only when it reaches the

randomly predefined destination.randomly predefined destination. The grid is large enough, so nodes rarely change direction.The grid is large enough, so nodes rarely change direction.

Estimation:Estimation: The location can estimated once – at the moment the The location can estimated once – at the moment the

sending is originatedsending is originated The location can be re-estimated after each hop on the The location can be re-estimated after each hop on the

route from sender to the target.route from sender to the target.

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ConclusionsConclusions The empiric results determined that sending data to the The empiric results determined that sending data to the

estimated location gives higher success rates than estimated location gives higher success rates than sending to the original locationsending to the original location

S O U R C E - A C C E S S - T A R G E T (WITHOUT REPLY)

92

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100

1.0 1.2 1.4 1.6 1.8 2.0


succ

ess

rate

[%]

found

received (estimated location)

received (absolute location)

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CacheCache The nodes that are located during reactive The nodes that are located during reactive

requests are stored in cache of the nodes in the requests are stored in cache of the nodes in the routeroute

During the reactive requests, FL/GF are initiated During the reactive requests, FL/GF are initiated only if the searched node is not found in cache only if the searched node is not found in cache

When cache is activated, the timeout parameter When cache is activated, the timeout parameter defines when the data stored in cache is valid and defines when the data stored in cache is valid and when it is notwhen it is not

ConclusionsConclusions Naturally the Naturally the found found success rates are higher and success rates are higher and

the the received received success rates decrease when cache success rates decrease when cache option is activatedoption is activated

Yet, the economy of the system resources Yet, the economy of the system resources (forwardings per packet) is significant(forwardings per packet) is significant

The final decision is a matter of users’ needs and The final decision is a matter of users’ needs and resourcesresources

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Functionality Functionality Updates/Additions - contdUpdates/Additions - contdN U M B E R O F F O R W A R D I N G S P E R P A C K E T

A N D F O U N D S U C C E S S R A T E SB Y F L M O D U L E U S I N G C A C H E

0

25

50

75

100


succ

ess

rate

s [%

]

total found

found by FL

found in cache

3.517.57 8.45 9.956.13

18.0514.01

8.93

1 1.414 1.732 2

forwardings per packet -cache enabled

forwardings per packet -cache disabled

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Core and FL Queues Core and FL Queues Each time a node sends a packet it is copied Each time a node sends a packet it is copied

to the relevant queueto the relevant queue When the node makes sure the next hop has When the node makes sure the next hop has

received the packet (by “hearing” next hop received the packet (by “hearing” next hop redirecting the packet), it is deleted from redirecting the packet), it is deleted from the queuethe queue

In case the packet was not deleted from the In case the packet was not deleted from the queue during timeout interval, it is being queue during timeout interval, it is being rescheduledrescheduled

MotivationMotivation The optimization prevents discontinuances The optimization prevents discontinuances

in packet transmissionin packet transmission

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Example: disconnection of transmissionExample: disconnection of transmission

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300

g

sender

rece

iver

packetlost

the expected receiver the expected receiver gets out of the gets out of the transmission range transmission range => the packet is lost => the packet is lost

there are no nodes in the there are no nodes in the transmission range of the transmission range of the receiverreceiver=> the packet is lost => the packet is lost

a g

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300

g

sender

a packetlost

h

rece

iver

rece

iver

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ConclusionsConclusions The empiric results determined that all success rates The empiric results determined that all success rates

were improvedwere improved No resource overheadNo resource overhead

F O U N D S U C C E S S R A T E SW I T H / W I T H O U T N E X T H O P Q U E U E S

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number of nodes

succ

ess

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te [%

]

Next HopQueues ON

Next HopQueues OFF

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Functionality Functionality Updates/Additions - contdUpdates/Additions - contd Bypass – Core and FL Bypass – Core and FL

The optimization is used when there are no available The optimization is used when there are no available nodes (receivers) in the sending directionnodes (receivers) in the sending direction

When the mode is activated, the sender chooses an When the mode is activated, the sender chooses an alternative route that exceeds the strip limit and alternative route that exceeds the strip limit and bypasses the dead areabypasses the dead area

The route returns to the original strip as soon as The route returns to the original strip as soon as possiblepossible

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400

a e

c

b d

FL B

PBP

FL

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ConclusionsConclusions The empiric results determined that using bypass The empiric results determined that using bypass

optimization improves the success rates. The optimization improves the success rates. The improvement is most significant in the medium grid improvement is most significant in the medium grid spacesspaces

F O U N D A N D R E P L I E D S U C C E S S R A T E SW I T H / W I T H O U T B Y P A S S

90

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100 200 300 400 500

number of nodes

su

cce

ss r

ate

[%

]

found - BP ON

found - BP OFF

replied - BP ON

replied - BP OFF

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Validate DBValidate DBThe entry is defined as not a valid The entry is defined as not a valid neighbor and being deleted from the neighbor and being deleted from the node’s DB lists (one-hop neighbors and node’s DB lists (one-hop neighbors and strips) strips) by Locationby Location

When estimated location exceeds the limits of the When estimated location exceeds the limits of the neighbors listsneighbors lists

Estimated location is being calculated based on the Estimated location is being calculated based on the DB current and previous locationsDB current and previous locations

by Timeby Time Timeout after the last updateTimeout after the last update

ConclusionsConclusions The empiric results determined that the The empiric results determined that the

reliability of the DB is higher when the reliability of the DB is higher when the neighbors lists are validated by Location and neighbors lists are validated by Location and by Timeby Time

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Two-hop neighbor tableTwo-hop neighbor tableAn extra table managed by Core module.An extra table managed by Core module. decreases the overhead of the reactive FL decreases the overhead of the reactive FL

modulemodule increases the overhead of the proactive Core increases the overhead of the proactive Core

modulemodule ResultsResults

Slightly higher success ratesSlightly higher success rates Significantly larger data-bases to maintainSignificantly larger data-bases to maintain Significantly higher overhead per packetSignificantly higher overhead per packet

ConclusionsConclusions The disadvantages supersede the advantagesThe disadvantages supersede the advantages

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Unstable NodesUnstable Nodes the basic assumption that all nodes are the basic assumption that all nodes are

available at all times is not accurateavailable at all times is not accurate in fact, nodes may turn on and off from time to in fact, nodes may turn on and off from time to

time due to numerous reasons (low battery, no time due to numerous reasons (low battery, no reception etc)reception etc)

to analyze real-life connectivity, portions of to analyze real-life connectivity, portions of nodes were defined as not reachable in nodes were defined as not reachable in random intervals of timerandom intervals of time

ResultsResults as it was expected the success rates are as it was expected the success rates are

inversely proportional to the number of the inversely proportional to the number of the non-stable nodes.non-stable nodes.

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S U C C E S S R A T E S V S N O D E S ' S T A B I L I T Y

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unstable nodes [%]

succ

ess

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te [%

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found

replied

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Porting to LinuxPorting to Linux

Motivation:Motivation: Failure to run simulations on large grid-spacesFailure to run simulations on large grid-spaces Enabling simulation control from remote locationEnabling simulation control from remote location Testing the results in different environmentsTesting the results in different environments

Overhead:Overhead: Reinstallation of NS2 under Linux environmentReinstallation of NS2 under Linux environment Porting of Octopus modules into NS2 under Porting of Octopus modules into NS2 under

Linux environmentLinux environment Adjustment of simulations’ scripts to Linux Adjustment of simulations’ scripts to Linux

environmentenvironment ConclusionsConclusions

The problem of simulations on large grid-spaces The problem of simulations on large grid-spaces was solvedwas solved

Simulation results found to be similar in both Simulation results found to be similar in both environmentsenvironments

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Development EnvironmentDevelopment Environment

PlatformPlatform The protocol is implemented in NS2, discrete event The protocol is implemented in NS2, discrete event

simulator targeted at networking researchsimulator targeted at networking research The protocol is written in C++ and OTclThe protocol is written in C++ and OTcl The test environment written in CShell and TclThe test environment written in CShell and Tcl The protocol and tests are supported in Cygwin and The protocol and tests are supported in Cygwin and

Linux environmentsLinux environments

System ParametersSystem Parameters Numerous system parameters were expected to impact Numerous system parameters were expected to impact

simulation results and needed fine-tuning based on simulation results and needed fine-tuning based on empirical experimentsempirical experiments

These parameters were defined so that they can be These parameters were defined so that they can be easily changedeasily changed

Among others, these parameters include Strip Among others, these parameters include Strip Resolution, Queues’ Timeouts, Number of Resolution, Queues’ Timeouts, Number of Retransmissions, Proactive Updates Intervals etc.Retransmissions, Proactive Updates Intervals etc.

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System ParametersSystem ParametersAs an example, the Strip Resolution was found to As an example, the Strip Resolution was found to be one of the most important parameters to be one of the most important parameters to influence on success ratesinfluence on success rates

S U C C E S S R A T E S V S S T R I P W I D T H

0.96

0.97

0.98

0.99

200 225 250 275 300

strip resuolution [m]

succ

ess

rate

[%

] static

mobile

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SimulationsSimulations

The following scripts were written in The following scripts were written in order to automate the process of running order to automate the process of running experimentsexperiments single_test.csh <parameter lists> - single_test.csh <parameter lists> -

responsible for setting the desired responsible for setting the desired configuration, running the experiment several configuration, running the experiment several times (for better accuracy), collecting and times (for better accuracy), collecting and processing the relevant statistical dataprocessing the relevant statistical data

test_all.csh <output file> - contains a list of test_all.csh <output file> - contains a list of single_test executions with different single_test executions with different parametersparameters

file.tcl file.tcl the actual input parameter to the NS2 applicationthe actual input parameter to the NS2 application responsible for randomly defining each node’s route responsible for randomly defining each node’s route

on the grid during simulationon the grid during simulation dynamically updated by single_test on each dynamically updated by single_test on each

executionexecution

o c t o p u s scalable routing protocol for wireless ad hoc networks

Documents

directions north

source node

node h

east table of node

northwest4 directions

simultaneously2 directions

time2 directions x

west east4 directions