Final paper-kerala_modified (Autosaved)

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Using Publish-Subscribe Model for Applications

in Mobile Adhoc Network

Swaroop R. Chougule

Walchand College of Engineering ,

Sangli

[email protected]

Prof. Mrs. M.A. SHAH


Sangli

[email protected]

Prof. Dr SM.Deshpande


Sangli

[email protected]

Abstract MANET is becoming an emerging trend to

cope with radio communications capabilityandincreasing

access to data in wireless network. The publish /subscribe

messaging paradigm has a number of characteristics that

make it very attractive in this internet world. These

include scalability, efficiency, decoupling between

publishing and subscribing entities, and the ability to

integrate a wide variety of devices and systems. In this

paper, we explore the application of the publish/subscribe

messaging paradigm. We present application of MUSIC

Shoppe which makes use of content based routing inpublish-subscribe paradigm. A middleware (REDS) is

used for experimentation.

Index Terms----MANET, Publish-Subscribe, ContentBased Routing (CBR), REDS

I.INTRODUCTION

A "Mobile Ad Hoc Network" (MANET) is an

autonomous system of mobile routers (and nodes, associated

hosts) connected by wireless links[1].The mobile nodes that

are in range of each other can directly communicate, whereas

others needs the aid of intermediate nodes to route theirpackets.

MANETs have no central point of administration, nor are

they supported by any fixed infrastructure. Instead, due to the

routing capabilities of the nodes themselves, the network is

self-organizing. Nodes that are not in each others radio rangemay communicate by means of multi-hop routing, in which

nodes that interconnect the communication partners aid in the

forwarding of data. Networking technologies and products

now enable a high degree of connectivity across a large

number of computers, applications, and users. In these

environments, it is important to provide asynchronous

communications for the class of distributed systems that

operate in a loosely-coupled and autonomous fashion, and

which require operational immunity from network failures.

This requirement has been filled by various middleware

products that are characterized as messaging, message

oriented middleware (MOM), message queuing, or publish-

subscribe.

II. Need of Content Based Routing in MANET

With the steady growth of consumer products such as

Laptop, PDA which acts as wireless mobile routers,

MANETs are becoming increasingly common and resources

are shifting towards the edge of network For this purpose,

need for efficient multi-hop routing protocols rises. Due to its

volatile nature, communicating over a MANET is unreliable

and takes a relatively long time, forming a highly unattractive

networking environment.The problem occurred in MANETs is that traditional

protocols i.e. whether it is in the application layer, networklayer etc are address-based and require that all

communication partners know each other. All applications

related ,that are mainly interested in what they exchange; notwith whom, in fact place a burden on routing that can often

be avoided. Internet radio stations, peer-to-peer file sharing

and group conferences are all examples of applications that

are mainly interested in what they exchange; not with whom.

Such applications may benefit from content-based routing

(CBR).In conventional systems, the sender explicitly specifies the

intended message recipients using a unicast or multicast address.Instead, in CBR the sender simply injects the message in thenetwork, which determines how to route it according to thenodes interests. These identify the relevant classes of messages

based on their content, e.g., using key-value pairs or regularexpressions.

There are many approaches of CBR to route content botheffectively (everyone gets the content they want) and

efficiently (content only reaches those parts of a network

where it is wanted). Systems are often compared by the

percentage of subscribers that get what they want (called the

completeness ratio), the percentage of messages that are

received that are actually wanted (called the precision ratio)

and the overhead that the systems routing scheme places on

the network (this includes the forwarding of the content

itself).

III PUBLISH-SUBCRIBE SYSTEM

Publish/subscribe (or pub/sub) is a messaging pattern

where senders (publishers) of messages are not programmed

to send their messages to specific receivers (subscribers).

Rather, published messages are characterized into classes,

without knowledge of what, if any, subscribers there may be.

Subscribers express interest in one or more classes, and only


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receive messages that are of interest, without knowledge of

what, if any, publishers there are. This decoupling of

publishers and subscribers can allow for greater scalability

and a more dynamic network topology.

In a content-basedsystem, messages are only delivered to

a subscriber, if the attributes or content of those messages

match constraints defined by the subscriber. The subscriber isresponsible for classifying the messages.

First we elaborate the terms related with this systema. Clients: They interact by publishing events and by

subscribing to the classes of events they are interested in.

b. Event dispatcher: It is a main component of the

middleware. It collects all the subscription ad forwards the

events to subscribe. It is responsible for collecting

subscriptions and forwarding events to subscribers.

Recently, many publish-subscribe middleware have

become available, which differ along several dimensions.

1. Subject-basedsystems, where subscriptions identify onlyclasses of events belonging to a given channel or subject.

2. Content-based systems, where subscriptions contain

expressions (called event patterns) that allow sophisticated

matching on the event content. In this the selection of a

message is determined entirely by the client, which usesexpressions (often called filters) that allow sophisticated

matching on the message content. Clearly, the message

format constraints the subscription language. For instance, if

the message is simply a string, then regular expressions are

the typical subscription language. Also, the expressive power

of the subscription language impacts the inner working of themiddleware. For instance, as described in [5], under some

conditions it is possible to detect that a filter is subsumed by

an already existing one, or even to fuse together two filters

into a more general one, thus reducing the matching space.

In this paper we assume a content-based subscription

language, as this represents the most general and challenging

case. The architecture of the event dispatcher can be either

centralized or distributed. In this paper, we uses distributedtype of architecture. In such middleware a set of dispatching

servers are interconnected in an overlay network &

cooperatively route subscription and event messages.

The systems exploiting a distributed dispatcher can befurther classified according to the interconnection topology of

dispatchers and the strategy exploited for message routing.

There are two Publish-subscribe routing strategies:

(a) Message forwarding

(b) Subscription forwarding

1. Message forwarding is a simplest approach in which

brokers are connected to form unrooted tree. Publishers send

messages to their associated broker, which forwards them to

all other brokers by following the tree topology. Moreover,

each broker keeps track of the subscriptions coming from thesoftware components directly attached to it into a local

subscription table, which is used to determine the

components, if any, that should receive incoming messages.

Requests to unsubscribe from a given event pattern are

handled and propagated analogously to subscriptions,

although at each hop entries in the subscription table are

removed rather than inserted. The main benefit of message

forwarding is that it does not require subscriptions to be

propagated.

But it has some disadvantages that highest overhead at

publishing time.

2. Subscription Forwarding is an alternative and more

widely used strategy which limits the overhead of messageforwarding by spreading knowledge about subscriptions

beyond the firstbroker, i.e. the broker where the publisher is

attached, along the un rooted tree connecting brokers.Specifically, when abroker receives a subscription from one

of the application components connected to it, not only it

stores the associatedpredicate into its subscription table as in

message forwarding,but also it forwards such a predicate to

the neighboringbrokers. During this propagation, each broker

message forwarding,but also it forwards such a predicate to

the neighboringbrokers. During this propagation, each broker

behaves as a subscriber with respect to its neighbors. This

process effectively sets up routes for messages through thereverse path followed by subscriptions. It has only one

drawback is that it fills the subscription tables of each broker.

But as compare to Message forwarding it is more

advantageous because it offers the best performance at

publishing time.To avoid confusion in the figure only brokers are shown,

without clients in Fig 1. A) and B) the above strategies are

compared by showing the same setting, characterized by a

distributed dispatcher composed of 16 brokers. Two of them,

namely S1 and S2, have components connected to them that

subscribed to the same predicate, represented as a blackcolor, while broker S3 received a gray subscription. Colored

arrows represent the content of subscription tables for the

corresponding filters. Broker P published a message matching

A) Message forwarding B) Subscription forwarding

Fig.1 A) and B) indicates that the Publish-subscribe routing strategies.

the black filter but not the gray one. The path followed by this

message is shown through thick, directed lines, while black

and gray arrows represent the content of subscription tables.

More specifically, each broker has a colored arrow oriented


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towards another broker if it received the corresponding

subscription from that broker. Figure 1(a) shows how

message forwarding incurs in the highest overhead at

publishing time, while it does not require subscriptions to be

propagated. Subscription forwarding (Fig. 1(b)) fills the

subscription tables of each broker but offers the best

performance at publishing time.

IV REDS MIDDLEWARE

The basic requirements of todays' distributed systems are

high degrees of decoupling and flexibility. One of the

solution to tackle all these issues is to use publish-subscribe

middleware. In this paper we provide the brief introduction to

REDS (Reconfigurable Dispatching System) middleware

which is basically meant for reconfiguration.

REDS (REconfigurable Dispatching System) is a framework

of Java classes to build publish-subscribe applications for

large, dynamic networks. REDS provides the client API to

write publish-subscribe applications and defines a general

framework of components, with clearly defined interfaces, to

build a distributed dispatcher organized as a set ofbrokers

linked in an overlay dispatching network, which collaborateto route messages from publishers to subscribers. REDS is

the first publicly available and implemented system expressly

designed to tolerate arbitrary topological reconfigurations of

the message dispatching network independently from the

underlying networking scenario.

The first approach of reconfiguration concerns the very

configuration of the middleware architecture, and addresses

the problem of enabling the selection of different mechanisms

for different deployment scenarios. Thus, for instance, it is

possible to select the routing strategy (or network transport,

or matching semantics, and so on) that is most appropriate for

the application at hand. Moreover, proper extension

mechanisms are in place that enables programmers to definetheir own variants, if needed.

The second reconfiguration approach concerns instead thedynamic reconfiguration of the topology of the message

dispatching network, and therefore addresses the needs of

highly dynamic systems where the topology of the network

undergoes continuous change (e.g., mobile and peer-to-peer

systems). This second form of reconfiguration will be

embedded in some of the components we develop for

scenarios in wireless networks. Here, classes used in current

REDS middleware are briefly explored, dispatching service-It

provides methods to open a connection with a REDS broker,

close it, get the identifier associated with the connection,

subscribe to and unsubscribe from a set of messages, get

messages dispatched to the component, and publish newmessages.Filter interface- It defines a method matches that is

supposed to be redefined with the filtering logic specified by

the implementing class. In addition, the methods hash code

and equals are used internally by REDS brokers to store and

compare filters.

Fig.2. Present REDS middleware Architecture

Comparable interface -This represents filters that can be

covered by others according to some notion of partial

ordering. Transport- (Transport and neighbor) this layer

provides the mechanisms used to transport messages,

(un)subscriptions, and any other kind of broker specificcontrol message through the network. Moreover, it also hides

the mechanisms used to address and access brokers and

clients, and to setup the dispatching network in case the

dispatcher is distributed.Routing - (Core, Router, Neighbored

and ConnectionManager and SubscriptionTable) CORE-the

interface Core abstracts the central component of a REDS

broker mediating the communication among the other

components, which therefore do not have direct visibility of

each other CONNECTIONMANAGER - the

ConnectionManager interface describes the component in

charge of managing the overlay dispatching network.

SUBSCRIPTION TABLE-SubscriptionTable providesmethods for inserting and removing filters, as well as for

selectively retrieve the filters that are relevant to a given

neighbor or set of neighbors, or those matching a given

message. NEIGHBOURSET-A convenience class provided

as a way to simplify the task of accessing, from within the

routing components, information concerned with the brokers

neighbors represented by Neighbor instances. SimpleCore-

The class implements a basic core that delegates all its

operations to the other components, i.e., the Router and the

ConnectionManager, without any additional processing.

Generic Table -The class implements the SubscriptionTableinterface by maintaining a list of all the filters received for

each neighbor. DeferredUnSubCM -This class implements

the deferred unsubscription strategy described in [7], but does


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not provide any mechanism to attempt reconnection of the

overlay network in presence of link failures.

ManetDeferredUnSubCM - It adopts the same strategy for

reconciling subscription tables, but includes also a

mechanism [24] to repair the overlay network, inspired by the

MAODV multicast protocol [31] and geared towards mobile

ad hoc networks.

V. EVALUATION

1. Experimentation Setup:We have performed the experiments using seven

desktop PCs connected in wired network. Different

scenarios have been developed, that uses five number of

brokers, single publisher and varying number of

subscribers. Results are analyzed depending on No. of

messages received and time of arraival.

The Music shopee application we developed is

analysed for subscription forwarding behaviour. Here

message published is list of artists and their hindi songs.Subscribers have selected artists according to their choice. As

a result of content based routing mechanism Songs of given

choice have been reached to individual subscribers. A

publication is allowed to traverse the system only if there are

data sinks, or subscribers, who are interested in the data.Subscribers indicate their interest using subscription

messages which are detailed below. If there are no interested

subscribers, the publication is dropped. A publication may

also contain an optional payload, which is a blob of binary

data. The payload is delivered to subscribers, but cannot be

referenced in a subscription constraintBefore a publisher can issue publications, it must supply

a template that specifies constraints on the publications it will

produce. These templates are expressed via advertisement

messages. In a sense, an advertisement is analogous to a

database schema or a programming language type.

The language model is based on the traditional [attribute,

operator, value] predicates used in several other content-

based publish/subscribes systems. In this,each messageconsists of a message header and a message body. The header

includes a unique message identifier, the mes-sage type

(publication, advertisement, subscription, or notification).The

content and for-mats of each message type are detailed below.Data producers, or publishers, encapsulate their data in

publication messages which consist of a comma separated set

of [attribute, value] pairs. Each publication message includes

a mandatory tuple describing the class of the message.

The class attribute provides a guaranteed selective

predicate for matching, similar to the topic in topic-based

publish/subscribe systems.

A publication that conveys

information about a music shopee listing may look as

follows:

Before a publisher can issue publications, it must supplya template that specifies constraints on the publications it will

produce. These templates are expressed via advertisement

messages. In a sense, an advertisement is analogous to a

database schema or a programming language type, and can

specify the type and ranges for each attribute as shown in the

following example:

A:[class:HINDI][ARTIST:@string][PAYLOAD:@string][

RATING:1-5] [YEAR: YYYY] [BITRATE: int]

The above advertisement indicates that the publisher will publish data related to HINDI songs with its artist, year,

rating and bitrates available. An advertisement is said to

induce publications: the attribute set of an inducedpublication is a subset of attributes defined in the associated

advertisement, and the values of each attribute in an induced

publication must satisfy the predicate constraint defined in the

advertisement. Note that a publisher may only issue

publications that are induced by an advertisement it has sent.

Two possible publications P1 and P2 induced by the above

advertisement are listed below, while P3 is not induced by the

advertisement due to the extra attribute film.

P1: class: HINDI][ARTIST:A][PAYLOAD:AB]P2: [class: HINDI]

[ARTIST:A][PAYLOAD:AB][YEAR:1989]

P3: [class: HINDI][ARTIST:A],[FILM:xx]

Subscribers express their interests in receiving publication

messages by issuing subscriptions which specify predicateconstraints on matching publications.

S: [class: HINDI][ARTIST:YHOO][PAYLOAD: @string]

Similar to publications, each subscription message has a

mandatory predicate specifying the class of the message, with

the remaining predicates specifying constraints on other

attributes [8].A publication is said to match a subscription, if all

predicates in the subscription are satisfied by some [attribute,

value] pair in the publication. For instance, the above

subscription is matched by publications of all songs by artist

A. A subscription is said to cover another subscription, if

and only if any publication that matches the latter also

matches the former. That is, the set of publications matching

the covering subscription is a superset of those matching thecovered subscription.

The Following graphs indcates results for different

scenarios. In the first scenario we considered single

publisher, no. of brokers and single subscriber. The publisher has published 100 messages. The graph (3.a)

shows time delay for messages to reach to the desired

subscriber.

In second scenario, we considered single subscriber and

publisher performing the same operations using the

previous parameters but with increased number of hops in

between. The results have been compared with previous one

and plotted as shown in the fig. 3 (b). The graph shows that

that the delay occured in forwarding messages in second

scenario was more than first one.Finally, running the third scenario by considering many

brokers,many clients and publisher attracts the same

explanation about routing strategy.Its results are also shown

in the fig 5(c).


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Fig. 3.a) One Subscriber and One publisher

Fig. 3. b) Two subscriber and One publisher

Fig. 3. c) Many subscriber and Many Brokers

The above graph showa result of operation. The

masseges published by publisher are first broadcasted to all

the brokers in wired nework.After publishing, the subscriber

subscribes to only those masseges he/she is interested in.

And based on connection topology betweeen them the

contents are routed to subscriber.

The encouraging results presented above in wired networkhave prompted us to develop the similar scenario in wireless

network. In our experiments, eight users participated by

carrying a laptop equipped with an 802.11g wireless card

configured in ad hoc mode and without any encryption. The

measured communication range was about 35 m. Users

moved in a 60 _ 150 m area in a park behind our department.

Therefore, the resulting network scenario was rather sparse.

Each user was instructed to move according to the Random

Waypoint mobility pattern, randomly choosing a target point

within the test area and walking toward it along a straight line

and with constant speed. Upon reaching the target, the userstopped for a random time between20 seconds and 60

seconds and then repeated the process. Traffic was generated

by a client installed on each laptop, publishing between 1 and24 msg/s.Subscriptions were allowed to change dynamically.The work is in progress and the preliminary results are encourage

ing.

CONCLUSION

From the above results it, can be seen that the delivery

time depends on the number of hops or the hop distance

between publisher and subscriber. Additional time is required

due to lookup in the subscription table to match the data

received from neighbour against the appropriate filter.The

message format for the data sent by the publisher gives theefficient way to handle the issue of subscription matching. It

also facilitates the subscriber to subscribe to particular fields

in the messages being received.The REDS system providesmechanism for reconfiguration in case of link or node failure

so this will be useful in case of wireless network where the

nodes are mobile.

VI.ACKNOWLEDGMENT

REDS is part of larger research collaboration with Paolo

Costa, Davide Frey, Matteo Migliavacca, Luca Mottola, and

Amy L. Murphy. Moreover, REDS developers include

Fabrizio Buzzi, Sandro Calzoni, Kubilai Hernandez, andAlessandro Monguzzi. The authors are deeply obliged with

all of the aforementioned people, especially to Prof.

Gianpaolo Cugola for his valuable discussion and guidance

about the topic of paper.

This work is supported by the AICTE under Research

Promotion Scheme (RPC) in 2008-09.

VII.REFERENCES

[1] C.-K. Toh. Ad hoc Mobile Wireless Networks . Prentice Hall PTR,Upper Saddle River, 2002.

[2] Roberto Baldoni, Roberto Beraldi, Leonardo Querzoni, GianpaoloCugola, Matteo Migliavacca. Content -Based Routing in Highly

Dynamic Mobile Ad Hoc Networks, October 24 2005

[3] Gianpaolo Cugola and Gian Pietro Picco .REDS: A ReconfigurableDispatching System. Dipartimento di Elettronica e Informazione,

Politecnico di Milano, Italy.

[4] Gian Pietro Picco ,Gianpaolo Cugola ,Amy L. Murphy. EfficientContent- Based Event Dispatching in the Presence of Topological

Reconfiguration. [5] Gianpaolo Cugola ,Gian Pietro Picco . REDS: A Reconfigurable

Dispatching System

[6] Luca Mottola, Gianpaolo Cugola, and Gian Pietro Picco.A Self

Repairing Tree Topology Enabling Content -Based Routing in MobileAd Hoc Networks.

[7] Laurea thesis of:Luca Mottola ,id. 644048, Advisor: Prof. G.P.

Picco,Co-advisor: Prof. G. Cugola .Overlay Management for Publish-

Subscribe in Mobile Environments. Academic year 2003-2004

[8] Hans-Arno Jacobsen, Alex Cheung, Guoli Li, Balasubramaneyam

Maniymaran, Vinod Muthusamy, Reza Sherafat Kazemzadeh The

PADRES Publish/Subscribe System


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