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3 Existing Middleware Technologies Hardware Domain-Specific Services Common Middleware Services Distribution Middleware Host Infrastructure Middleware Operating Systems & Protocols Applications Middleware TypeExamples Message PassingMessage Passing using TCP/UDP Remote InvocationJava RMI, CORBA Asynchronous Notifications CORBA AMI Shared SpacesLinda, Java Spaces Message QueuingIBM MQ-Series Goal is to provide identity, time, and synchronization decoupling Above mentioned middleware technologies do not provide all three simultaneously.
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State-of-the-art in Publish/Subscribe Middleware for Supporting Mobility
Sumant Tambe
EECS Preliminary ExaminationDecember 11, 2007
Vanderbilt University, Nashville, TN, USAContact : sutambe@dre.vanderbilt.edu
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Information Dissemination Systems Examples of Information Dissemination
Systems Online traffic information Stock price tracker News feeds Airline schedule display Pervasive computing
Characteristics of Information Dissemination systems Information publishers Large number of information subscribers Inherently one-to-many Anonymous publishers and subscribers Asynchronous communication
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Existing Middleware Technologies
Hardware
Domain-SpecificServicesCommon
Middleware ServicesDistribution
MiddlewareHost Infrastructure
MiddlewareOperating Systems
& Protocols
ApplicationsMiddleware Type Examples
Message Passing Message Passing using TCP/UDP
Remote Invocation Java RMI, CORBA
Asynchronous Notifications
CORBA AMI
Shared Spaces Linda, Java Spaces
Message Queuing IBM MQ-Series
Goal is to provide identity, time, and synchronization decouplingAbove mentioned middleware technologies do not provide all three
simultaneously.
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Publish/Subscribe Middleware Characteristics of
Publish/subscribe middleware Inherently multicasting (one-to-
many) Asynchronous communication
Time decoupling Identity decoupling Synchronization decoupling
Anonymous publishers Anonymous subscribers Implicit addressing
Types of Publish/Subscribe Channel-based Topic-based (subject based) Content-based Content-based with patterns Context-based (local state)
\Stocks\GroupA\MSFT
Company “MSFT”
Price >= $10
Volume >= 5000
My Account Balance >= $10,000
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Challenges in Information Dissemination Systems Supporting Mobility
Physical mobility of application components While online/offline
Potentially large number of publishers and subscribers
Frequent connections and disconnections To conserve power, bandwidth
Changes in underlying network topology Ad-hoc networks, (e.g., disaster
recovery) Support location-based services
Approximate location/range Limited time validity (e.g., roads
to downtown closed till 3 a.m.)
YOU ARE SOMEWHERE
HERE
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Solution Domain Challenges in Supporting Mobility (1/2)
Location transparency Many applications are location
independent (e.g., stock tracker) Completeness of events
Events should not be lost due to mobility or connection/disconnections
Retransmission should be avoided Ordering of events
Events should be delivered in the order of the sender
No duplicate delivery Due to rapid mobility
Responsiveness No QoS degradation No indirection (e.g., Mobile IP)
Publisher
Subscriber
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Solution Domain Challenges in Supporting Mobility (2/2)
Location-awareness E.g., Parking place notifications “Location” is the local context
(variable) Continuous change in location
Propagation of location dependent subscriptions Minimization of propagation
delay Approximate matching of
events Approximate subscriptions Approximate events
Existing Publish/Subscribe middleware although useful, but is
not adequate
S: (close to downtown Toronto) AND (about 75 square meters in size) AND (no more than $1000) AND (close to major grocery shopping)
E: (location, close to downtown) (size, big) (price, expensive) (shopping, close-by)
e3 should have been received
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Publish/Subscribe Middleware Solutions (1/2)
Creating overlay network of event brokers in dynamic environment Dynamic dispatching tree in JEDI
Selecting subscriber group leader Adapt to changing topology
SHOPPARENT algorithm Considers locality of subscribers Greedy, local optimizations only Heuristic-based overhead calculation
Location transparency Subscription handoff protocol in
REBECA Completeness guarantee Source FIFO order No duplicates
Brokers 3 & 4Share subscriptions
Brokers 4 & 5don’t share subscriptions
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