Opportunistic Networking : Data Forwarding in Disconnected

8/14/2019 Opportunistic Networking : Data Forwarding in Disconnected

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Opportunistic Networking :Data Forwarding indisconnected mobile ad

hoc networks


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Abstract

Opportunistic networks are on of the mostinteresting evolution of MANETs

Opportunistic network mobile nodes areenabled to communication with each node

Routes are built dynamicallymessage are en route between sender a

destinationNode can opportunistically be used as next

hop This method is to bring message closer to the

final destination


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Introduction

Research on multihop ad hoc network has afocused on a number of applicationenvironment

Originally conceived for military application,and aimed at improving battlefieldcommunication

Two main evolutions of multihop ad hocnetwork are mesh network and

opportunistic networkOpportunistic network no assumption is

made with regard to the existence of complete path between two nodes wishing

to communicationConce t of o ortunistic network come from


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Taxonomy of routing/forwardingtechniques for Opportunistic Network


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Delay-tolerant network

Delay-tolerant network (DTN) architectureconsists of

DTN RegionDTN Gateway

Use protocol stack that best suit theparticular infrastructure

DTN node overlay protocol is added on top of the traditional transport layer


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6


Architecture

Region A - InternetRegion A - Internet

Region B Sensor networkRegion B Sensor network

data

data

data

data

UserHost{A, UserHost}

{A, R1}

{B, R2}

{B, R3}

{D, R4}

{A, R2}

{C, R3}

{C, R4}

DTN gatewaySource : http://www-net.cs.umass.edu/~shyang/presentation_slides/DTN.ppt


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Example of delay-tolerant network


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Opportunistic Network

Opportunistic networking


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Realistic Case Studies

PSNs in the Haggle ProjectWildlife Monitoring :

ZebranetSWIM

Opportunistic Network for Developing AreasDarkNetSaami Network Connectivity (SNC)


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Realistic Case Studies

Research on opportunistic network isdevoting particular attention to realisticcase study

On of the basic component realistic casestudies are mobility models

Design of efficient forwarding algorithm aswell as to perform realistic simulation

Researchers are also implementing a numberof real-application scenarios inopportunistic network

For example, with wildlife trackingapplication


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Haggle Project

It targets solutions for communication inopportunistic network

Funded by European Commission in theframework of the FET-SAC

Studying the properties on Pocket SwitchedNetworks (PSNs)

Pair-wise modeling contacts between devices


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Wildlife Monitoring : ZebraNet

Biologists want to track animalsLong-termOver long distances

Questions:Interactions within a species?Interactions between species?Impact of human development?

Source : http://www.princeton.edu/~mrm/zebranet.html


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Wildlife Monitoring : ZebraNet

Source : http://www.princeton.edu/~mrm/ZNetASPLOS.pdf


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ZebraNet Protocols

Two peer-to-peer protocols evaluated hereFlooding : Send to everyone found in peer

discovery.History-Based : After peer discovery, choose

at most one peer to send to per discoveryperiod: the one with best past history of delivering data to base.

Simulation results show that both protocolsoutperform the directly protocol

History-based protocol outperforms floodingin term of bandwidth and energyconsumption


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Wildlife Monitoring : SWIM

In the Shared Wireless Infostation Model(SWIM) whales are monitored.

Data is replicated and diffused (similar to theflooding protocol in ZebraNet)

Both whale-to-whale and whale-to-base-station communications are allowed

No experimental result are actually availablebut simulation results are quite realisticsince simulation parameter set accordingto studies conducted by biologist whalesreal habits


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Opportunistic Network for DevelopingAreas : Darknet

It aims to provide a low-cost InternetConnectivity to rural villages in India

Kiosks are built up and equipped digitalstorage and short-range wirelesscommunication

MAPs exchange data with the kioskswirelessly

MAPs can download/upload data to theInternet when passing by APs in a nearbytown

It supports Internet/Intranet messaging,distribution and collection information


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Opportunistic Network for DevelopingAreas : SNC

It aims to provide network connectivity to thenomadic Saami population of the reindeerherders

Providing network connectivity is a mean toprotect their habits, culture and tradition

In its initial stage, it focused on providingemail, file transfer, and cached webservices

It should finally be noted that the SNC projectfocuses on a pure DNT architecture


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Dissemination-Based Routing

Based on data dissemination performdelivery a message to destination bydiffusing it all over the network.

No knowledge of a possible path todestination and nor of appropriate of next-hop

Works well on mobile networkLimits message delay but is resource hungry.May lead to network congestion


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Dissemination-Based Routing

Such asEpidemic Routing ProtocolMV Routing ProtocolNetwork Coding-Based Routing Protocol


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Epidemic Routing protocol

Goal is to deliver messages with highprobability even when there is never a fullyconnected path.

Give a message copy to every nodeencountered

essentially: flooding in a disconnectedcontext

Source : http://www.cise.ufl.edu/~helmy/cis6930-09/Epidemic-and-Ferry.ppt


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Mv routing protocol

A further step beyond epidemic routingMessages exchanged during pair-wise

contacts as in epidemic routing but usemore sophisticated method to selectmessages to forward to a

Deliver probability is relied on recent-pastobservation of both meeting betweennodes and the visits of nodes to

geographical locationA similar approach is followed in PROPHET

routing protocol


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Network coding-based protocol

Takes an original approach to limit messageflooding

Outperform flooding as it is able to deliverthe same information with a fewer numberof messages infected into the network

See example on next slide


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Example of network-coding efficiency


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Context-based routing

Exploits more information about the contextso as to identify suitable next hops towardsthe destinations (e.g., the home address of a user)

Reduce messages duplication Tend to increase the delay that each

message experience during deliveryDue to errors and inaccuracies in selecting

the best relays


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Context-based routing (contd.)

Nodes maintain a state in order to keep trackof the utility values

Need storage capacity for both state andmessages

Cost to hold and update the state at eachnode (overhead)


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Context-aware routing (CAR) Protocol

Each node is in charge of producing deliveryprobabilities towards each destination host

Delivery probabilities are exchanged so thatnode compute the best carrier fordestination node based on the nodescontext

When the best carrier receives a message, itstores it in a buffer and forwards it to the

destination node when metCAR provides a framework for computing

next hop based on the multiattribute utilitytheory


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Mobyspace : mobility pattern spacerouting protocol

The nodes mobility pattern is the contextinformation used for routing

The protocol builds up a high dimensionalEuclidean space

Each axis represents a possible contactbetween a couple of nodes

The distance along an axis measures theprobability of that contact to occur


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Example scenario

Source : http://jeremie.leguay.free.fr/lip6/files/poster_sigcomm05.pdf


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Node mobility pattern

Source : http://jeremie.leguay.free.fr/lip6/files/poster_sigcomm05.pdf


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Routing with infrastructure

Routing based on fixed infrastructureRouting based on mobile infrastructure

(carrier-based routing)


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Routing based on fixed infrastructure

A source node delivery a message keeps ituntil it reach a base station belonging tothe infrastructure

Then forwards the message to itBase station are gateways towards less

challenged networks (e.g. connected to aLAN)

The goal of an opportunistic routingalgorithm is to delivery messages to thegateways, which are able to find thedestination more easily


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Two variations of the protocol

1. First, only node-to-base-stationcommunications

Work as described abovemessages experience high delays

The example of this approach is theInfostation model


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Routing based on mobile infrastructure(carrier-based routing)

Nodes of the infrastructure are mobile datacollectors

They move around in the network area andgather messages from the nodes they passby

These special nodes are referred to ascarriers, supports, forwarders, MULEs, oreven ferries

They are entities responsible for messagesdelivery


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Routing based on mobile infrastructure(carrier-based routing) contd.

Node-to-carrier communicationshelp increasing connectivity in sparse

network and guaranteeing that isolatednodes be reached

delivery of messages is accomplishedBoth by carriers and ordinary nodesBoth node-to-node and node-to-carrier


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The data-mule system

Focus on data retrieval from sparse wirelesssensor networks

Consist of a three-tire architecture:The lower level : sensor nodes periodically

perform data sampling from the surroundingenvironment

The middle level : mobile agents (MULEs)move around in the area to gather theirdata

The upper level : a set of wired Aps and datarepositiories which receive information fromthe MULEs and connected to a central datawarehouse


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The message-ferrying approach

Extra mobile nodes (message ferries) areexploited to offer a message relayingservice

Nodes move around in the network They collect messages from source nodes


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Message collection happen intwo ways:

Node-initiated message ferrying :the ferry node moves around a predefined and

known pathEach node has knowledge of the path by

ferriesnode moves to meet ferries when it has data

to deliver

Ferry-initiated message ferrying :source node sends a ServiceRequest and

current position to the ferrythe ferry changes trajectory to meet the

source node


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Conclusion

Taxonomy of routing/forwarding techniquesfor opportunistic networks : without andwith infrastructure

Interesting is how to design multitieropportunistic networks

The data MULEs and message-ferryingarchitectures are the most promisingapproach

In the data MULEs approach, lower levelnodes exploit the higher level and mobiledevice(the MULEs)


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Future trends

Each level of the infrastructure is anopportunistic network in which nodes mayexploit routing algorithms to communicate

and may rely on the upper levels of theinfrastructure to reach nodes are too faraway


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Future trends (contd.)

For example, lower level : devices (e.g. PDA,smart phone)

An opportunistic routing algorithm makedevices to communicate with each other

Higher level : city-bus network might be used, bus act as MULEs

City-bus network might exploit further levelsuch as mesh network

Opportunistic network might representa fundamental building block for the next-generation internet

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Opportunistic Networking : Data Forwarding in Disconnected