1. THE DESIGN OF AN
INFORMATION SHARING
SYSTEM FOR
HUMAN NETWORKS
Presented by,
RESHMA FRANK
S7, CSE-β
RollNo:34
2. 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
3. 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
4. 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.
5. 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.
6. 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
7. THE ARCHITECTURE OF HUNET
• It’s a dynamic networks
composed of human-carried
wireless devices.
• Applications in HUMNETs
require content-based networking
services
9. 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
10. 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.
11. 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
12.
13. 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 )
15. 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)
16.
17. 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 .
18. 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.
19. 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
20. 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.
21. 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.
22. 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.
23. 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.
24. 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.
25. 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)
27. 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.
28. 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.
29. 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.
30. 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.
31. 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.
32.
33. 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.
34. 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.
35. 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.
36. 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.
37. 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.
Editor's Notes
because the information
source is unaware of the users who are interested in the
information;
3) which is prohibitive in HUNETs because they
consume excessive resources and the needed data are
usually impossible to get
. (style of communication that associates source and destination pairs based on actual content and interests, rather than letting source nodes specify the destination)
since we are unable to trace the associated keys of set bits.