THE DESIGN OF AN INFORMATION SHARING

SYSTEM FOR HUMAN NETWORKS

Presented by,RESHMA FRANKS7, CSE-βRollNo:34

INTRODUCTION• Existing mobile devices rely on the

wireless infrastructure to access Internet services provided by central application providers

• This architecture is inefficient in many situations

INTRODUCTION•Human network (HUNET) A network architecture that enables

information sharing between mobile devices through direct interdevice communication.

• Does not rely on the wireless infrastructure to access Internet services provided by central application providers

EXISTING SYSTEM

• DELAY TOLERANT NETWORKS [ DTNs]

“STORE-AND-FORWARD” approach ,where data is incrementally moved and stored throughout the network in “hopes” that it will eventually reach its destination.

LIMITATIONS OF THE EXISTING ARCHITECTURE

1)DTNsdo not support interest-driven communication.

2)DTN routing is based on the end-to-end model which is not applicable in HUNETs

3)DTN routing protocols require complex offline

processing to achieve optimal performance.

PROPOSED SYSTEM

• HUNET-a novel network architecture that facilitates efficient information sharing between portable mobile devices.

• B-SUB-an interest-driven information sharing system for HUNETs, a content-based publish/subscribe that achieves infrastructure-less communication between mobile devices.

• Temporal Counting Bloom filter (TCBF) -to facilitate efficient data dissemination

THE ARCHITECTURE OF HUNET

• It’s a dynamic networks composed of human-carried wireless devices.

• Applications in HUMNETs require content-based networking services

THE ARCHITECTURE OF HUNET

CONTENT-BASED NETWORKING

• The flow of messages through the network is driven by the content of the messages, rather than by explicit addresses

• receivers declare their interests to the network by means of predicates

• senders simply inject messages into the network• The network is responsible for delivering to each

receiver any and all messages matching the predicate declared by that receiver

CONTENT-BASED PUBLISH\SUBSCRIBE (CBPS)

• Content-based matching is the problem of finding all the subscriptions that match a given notification.

• CBPS represents a compromise between the extremes of publisher-side filtering of messages ( with event directly transmitted to interested subscribers ) and subscriber-side filtering of messages ( with events broadcasted to all subscribers ).

• Event delivery is the task of delivering the notification to the set of interested subscribers selected with content-based matching.

THE ARCHITECTURE OF HUNET[conti]

•A swarm of nodes form a mobile broker network.

•Multiple nodes serve as brokers to carry messages for users.

•Information sharing system for HUNETs-BLOOM-FILTER-BASED PUBLISH/SUBSCRIBE

HOW THE B-SUB

WORKS?????????

BLOOM FILTER-BASED PUB-SUB

[B-SUB]

• It’s a content-based publish-subscribe system.

• In B-SUB, messages are identified by using strings that summarize their contents. ( called keys )

B-SUB COMPONENTS

B-SUB COMPONENTS … cont,

1)Broker Allocation:• Group of socially active nodes are selected to be

brokers.

• Brokers are responsible for collecting interests and forwarding messages

• A Broker stores a TCBF for propagating other users’ interests. (which is called relay filters)

DESIGN OF

TEMPORAL

COUNTING BLOOM

FILTER[TCBF]…..

BLOOM FILTERS [BF]• A space-efficient probabilistic data

structure that is used to test whether an element is a member of a set or not.

• BF maps a key through multiple hash functions into a bit vector of a few bits being set.

• User’s interests are represented as keys .• Messages are identified by strings that

summarize their contents called as Keys .

BLOOM FILTER OPERATIONS

• The basic bloom filter supports two operations: test and add.

• Test -To check whether a given element is in the set or not.

• If it returns:

False, then the element is definitely not in the set.

True ,then the element is probably in the set.

• Add simply adds an element to the set.

BLOOM FILTERS (BF) … CONT,

• The locations of the set bits are determined by the hash functions.

• A query of a key to a BF checks if all the hashed bits of the key are set, which indicates if the key is contained in the BF

COUNTING BLOOM FILTERS [BF] … CONT,

• The basic BF doesn’t support deletions

• The counting bloom filter (CBF) is proposed to provide deletion.

• In a CBF each bit is associated with a counter, which will be set to an Initial counter value

• To delete a key from a CBF we decrement the counters of the key’s hashed bits. A bit will be reset once its counter reaches 0.

TEMPORAL COUNTING BLOOM FILTER (TCBF)

• Extension to BF, proposed to perform content-based networking tasks.

• It only supports temporal deletion.

• A filter constantly decrements the counter’s values of all its set bits, which is called Decaying

• B-SUB uses TCBF to encode user’s interest & embed information needed for brokers to make forwarding decisions.

DECAYING FACTOR (DF)

• The decay of a TCBF is to constantly decrement its counters’ values with a rate given by the decay factor (DF).

• If decaying is not used, the counters of the set bits don’t change after being set, then no interests will be removed.

• An obvious consequence is that a broker will end up with carrying the interests from the users that it meets rarely.

DECAYING FACTOR [DF]…CONT,

• Suppose that each message has a delay limit of time T, we should set the DF in such a way that an interest will get removed after T

• If the broker contains the interest, then the broker should meet a consumer that is interested in it within T.

• If a message is forwarded by the broker it’s likely that the message will be delivered within T.

HOW BLOOM FILTERS WORK?“Message Forwarding”

• B-SUB makes forwarding decisions through querying the TCBFs

• When a broker meets a consumer, the broker requests a TCBF containing the consumer’s interests, then forwards the matched messages to the consumer.

• The operations performed are only hashing and table lookup.

• Message are removed from brokers’ memory after being forwarded to prevent excessive copies in the network.

BLOOM FILTER-BASED PUB-SUB [B-SUB] …Cont,

• Advantages:

1- Frees users from addressing & routing tasks. (reduces the overall overhead in the system)

2- Message producers & consumers are separated.

3- Messages are forwarded only by brokers (Perform content matching for the users)

B-SUB COMPONENTS … Cont,

2)pub-sub forwarding

INTEREST PROPAGATION

• A user stores its own interests in a TCBF, which is called the genuine filter.

• A broker stores the interests collected from

other users in another TCBF called the relay filter.

• TCBFs serve as a “compressed” matching hint for delivery.

INTEREST PROPAGATION

• Exchange of TCBFs that contain their genuine interests and relay interests.

• A then merges Bs genuine interests and relay interests with its own relay interests.

• All operations are performed on the TCBFs instead of the raw strings that are corresponding to the interests.

MESSAGE FORWARDING

• When two nodes meet, they exchange their relay interests and genuine interests encoded in TCBFs.

• Let A and B to denote the two nodes.

• At first, node A queries all of its buffered messages against the genuine filter of B, and then forward all the messages that match the filter to B.

• A then examines Bs relay filter to determine which other messages should be forwarded to B.

MESSAGE FORWARDING

• The query that checks if a key is in a TCBF is called the existential query (E-query).

• the preferential query (P-query).• For a key k and two TCBFs, Fi and Fj, we get

the values of the counters associated with k in Fi and Fj, which are two sets, Ci and Cj.

• We obtain the minimum values of Ci and Cj, which is denoted as ci and cj.

MESSAGE FORWARDING

• A maintains a table of the preference values of all of the buffered messages, which is called a preference table.

• For each of the messages that have not been forwarded to B, A performs a preferential query of the message’s tag to the relay filter of B, and then compares the obtained preference value to the one associated with the message in the preference table.

• If Bs preference value is larger, the message is forwarded to B, and the preference value of the message in the preference table is updated to Bs preference value.

• Otherwise, the message will not be forwarded.

WHAT HAPPENS IF A

HACKER ATTACK

OCCURS??????????

PRIVACY GUARANTEE IN HUNET

• The basic privacy guarantee provided by the original B-SUB is called NON-DIRECT LINKAGE.

• the attacker cannot obtain direct linkage between a user’s identity and his/her interests.

• The attacker cannot reverse back the hashed bit-vector to the real interests.

• Interests gathered by an attacker are encoded.

B-SUB WITH PRIVACY GUARANTEE[B-SUB-P]

• An extension of B-SUB that provides stronger privacy guarantee.

• B-SUB-P mixes the user’s own interests and relayed interests when two encountered nodes exchange interests.

• When two nodes meet, say node A and B, B sends a single TCBF to A instead of two as the original B-SUB does.

• This filter is obtained by merging Bs genuine interests and relay interests which is called the MIXED RELAY INTERESTS.

B-SUB WITH PRIVACY GUARANTEE[B-SUB-P]

• The mixed relay interests do not disclose the linkage between node Bs identity and its interests, because A cannot distinguish between Bs own interests and its relayed interests.

• That is, A cannot guess Bs interests.

• A then performs a preferential query to determine what messages should be forwarded to B, which is the same as what the original B-SUB does.

CONCLUSION• B-SUB is an interest-driven information sharing

system for HUNETs.• It employs content-based networking to achieve

infrastructure-less communication between mobile devices.

• BSUB employs a tag-based content description model.• The TCBF, is invented to compress user interests and

guide content routing. • The use of TCBF reduces the memory and bandwidth

consumption of B-SUB.

REFERENCES

[1] K. Fall, “A Delay-Tolerant Network Architecture for ChallengedInternets,” Proc. Conf. Applications, Technologies, Architectures, andProtocols for Computer Comm., pp. 27-34, 2003.

[2] A. Carzaniga, D.S. Rosenblum, and A.L. Wolf, “Content-BasedAddressing and Routing: A General Model and its Application,”2000.

[3] P.T. Eugster, P.A. Felber, R. Guerraoui, and A.M. Kermarrec, “TheMany Faces of Publish/Subscribe,” ACM Computing Surveys,vol. 35, no. 2, pp. 114-131, 2003.

[4] A. Carzaniga, D.S. Rosenblum, and A.L. Wolf, “Design andEvaluation of a Wide-Area Event Notification Service,” ACMTrans. Computer Systems, vol. 19, pp. 332-383, Aug. 2001.

[5] B.H. Bloom, “Space/Time Trade-Offs in Hash Coding withAllowable Errors,” Comm. ACM, vol. 13, no. 7, pp. 422-426, 1970.

THANK

YOU…..

QUERIES?????