Adaptive Directory Services for Highly Dynamic Environments

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Adaptive Directory Services for Highly Dynamic
Environments

• Fabio Kon
• kon_at_ime.usp.br
• Department of Computer Science
• University of São Paulo, Brazil
• http//gsd.ime.usp.br
• Dilma M. Silva
• dilma_at_watson.ibm.com
• IBM T. J. Watson Research Center

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Directory Services

• Locate objects based on their name and/or
  attributes
• Analogous to phone directories
• White pages CORBA Name Service
• Yellow pages CORBA Trader
• Popular Directory Services
• LDAP / X.500
• CORBA Trading Object Service
• Jini Lookup Service

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Problems in Mobile and Highly Dynamic Environments

• Directory services help clients locate server
  objects
• But in dynamic environments
• Servers are dynamically added and removed
• Servers crash or become unreachable
• Servers may migrate from one node to the other
• Clients may move while they are looking for
  appropriate servers

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Motivation and Objective

• Existing Directory Services are not prepared to
  deal with such dynamic environments.
• With mobile and ubiquitous computing, dynamic
  environments will become more and more common.
• Objective investigate what facilities must be
  added to existing systems to support such
  dynamism.

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Target ApplicationThe Sidam Project Prototype

• Road Traffic Information System
• Motivation
• São Paulo is a city of 17M people.
• Road traffic is a complete chaos.
• Billions/year are lost in traffic jams.
• Goal
• Develop a prototype of a very-large-scale system
  to provide relevant information about traffic
  conditions in real-time to mobile users.

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Traffic Information System

• Highly replicated (millions of users)
• No Centralized Service
• Strict consistency not possible
• Some consistency is required data that is too
  old is useless
• Extremely distributed
• Production of data
• Consumption of data

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The Java Prototype

• Information Servers
• Hold traffic information for a few neighbourhoods
• Location Servers
• Used by clients to locate Information Servers
  based on the region of the city in which the
  client is interested
• A Directory Service of Information Servers

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Support for Dynamic Reconfiguration and Adaptation

• Consistency objects are responsible for
  implementing different consistency policies
• When Information Servers are killed, the system
  reconfigures itself dynamically to update the
  directory service

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Ongoing Work

• Trigger automatic reconfiguration when any
  component in the system fails.
• Creation and destruction of Information and
  Location Servers according to system load.
• Migration of components according to load and
  physical location of clients.
• Goal increase availability and response time of
  the system.

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For more information

• Fabio Kon kon_at_ime.usp.br
• SIDAM Web site
• http//www.ime.usp.br/sidam
• Distributed Systems Group Web site
• http//gsd.ime.usp.br