Design of an information system for HUNETs

THE DESIGN OF AN
INFORMATION SHARING
SYSTEM FOR
HUMAN NETWORKS
Presented by,
RESHMA FRANK
S7, CSE-β
RollNo: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

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
PUBLISHSUBSCRIBE (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

Design of an information system for HUNETs

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
Broker Allocation
Pub – Sub
forwarding
Interests
propagation
Message
forwarding
TCBF

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)

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.

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 Challenged
Internets,” Proc. Conf. Applications, Technologies, Architectures, and
Protocols for Computer Comm., pp. 27-34, 2003.
[2] A. Carzaniga, D.S. Rosenblum, and A.L. Wolf, “Content-Based
Addressing and Routing: A General Model and its Application,”
2000.
[3] P.T. Eugster, P.A. Felber, R. Guerraoui, and A.M. Kermarrec, “The
Many 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 and
Evaluation of a Wide-Area Event Notification Service,” ACM
Trans. Computer Systems, vol. 19, pp. 332-383, Aug. 2001.
[5] B.H. Bloom, “Space/Time Trade-Offs in Hash Coding with
Allowable Errors,” Comm. ACM, vol. 13, no. 7, pp. 422-426, 1970.

Design of an information system for HUNETs

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