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CTIS 490 DISTRIBUTED SYSTEMS

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Title: CTIS 490 DISTRIBUTED SYSTEMS


1
CTIS 490DISTRIBUTED SYSTEMS
  • WEEK 2
  • DISTRIBUTED SYSTEMS
  • ARCHITECTURES

2
INTRODUCTION
  • Distributed systems are complex pieces of
    software where components are dispersed across
    multiple machines.
  • It is crucial that these systems are properly
    organized.
  • There has to be a distinction between the logical
    organization of the collection of software
    components and the actual physical realization.

3
SOFTWARE ARCHITECTURES
  • A component is defined as a modular unit with
    well defined interfaces that is replaceable
    within its environment.
  • A connector is described as a mechanism that
    mediates communication, coordination, or
    cooperation among components.
  • Using components and connectors, we can classify
    various distributed architectural styles.

4
SYSTEM ARCHITECTURES
  • Basically, software architectures can be realized
    in two ways
  • Centralized Architectures
  • Decentralized Architectures

5
CENTRALIZED SYSTEM ARCHITECTURES
  • A server is a process implementing a specific
    service, for example a file system service or a
    database service.
  • A client is a process that requests a service
    from a server by sending it a request and
    subsequently waiting for the servers reply.

6
APPLICATION LAYERING
  • In general, a client-server architecture has
    three logical layers
  • The user-interface level
  • The business/processing level
  • The data level

7
EXAMPLE INTERNET SEARCH ENGINE APPLICATION
LAYERING
8
MULTITIERED ARCHITECTURES
  • How do we distribute a three level client-server
    application on the physical machines?
  • The simplest organization is to have only two
    types of machines
  • A client machine containing only the programs
    implementing the user-interface level.
  • A server machine containing the rest, that is the
    programs implementing the processing and data
    level.

9
CLIENT-SERVER ORGANIZATIONS
  • Thin clients-----------------------------------Fat
    clients

10
DECENTRALIZED SYSTEM ARCHITECTURES
  • A decentralized architecture is a peer-to-peer
    (P2P) system which use the computing power and
    bandwidth of the participants in the network.
  • This model differs from the client-server model
    where communication is usually to and from a
    central server.
  • P2P systems represent a paradigm for construction
    of distributed systems and applications in which
    data and computational resources are contributed
    by many hosts on the network (Intranet or
    Internet).
  • P2P refers to a class of systems and applications
    that employ distributed resources to perform a
    function in a decentralized manner.

11
APPLICATIONS OF PEER-TO-PEER SYSTEMS
  • File sharing (music, video, etc.)
  • Examples Napster, Gnutella, Freenet, and KaZaA
  • Process sharing (data analysis, scientific
    computing, etc.)
  • Examples SETI_at_Home
  • Collaborative environments (instant messaging,
    teleconferencing, etc.)
  • Examples Microsoft Meeting and Yahoo Messenger

12
CLASSIFICATION OF PEER-TO-PEER SYSTEMS
  • Hybrid Peer-to-Peer Systems
  • Has a central server that keeps information on
    peers and responds to requests for that
    information.
  • Pure Peer-to-Peer Systems
  • A pure P2P network does not have the notion of
    clients or servers, but only equal peer nodes
    that simultaneously function as both clients and
    servers to the other nodes on the network.
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