Download Peer-to-Peer VS Client/Server

Peer-to-Peer VS
Client/Server
Peer-to-Peer
• An alternative to the client/server model of distributed
computing is the peer-to-peer model.
• Client/server is inherently hierarchical, with resources
centralized on a limited number of servers.
• In peer-to-peer networks, both resources and control are
widely distributed among nodes that are theoretically
equals. (A node with more information, better
information, or more power may be “more equal,” but
that is a function of the node, not the network
controllers.)
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Decentralization
• A key feature of peer-to-peer networks is
decentralization.
This has many implications.
Robustness, availability of information and faulttolerance tends to come from redundancy and shared
responsibility instead of planning, organization and the
investment of a controlling authority.
• On the Web both content providers and gateways try to
profit by controlling information access. Access control is
more difficult in peer-to-peer, although Napster
depended on a central index.
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Technology Transition
The Client/Server Model
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The Peer-to-Peer Model
Classification
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Pure P2P vs. Hybrid (servers keep info)
Centralized  Napster
Decentralized  KaZaA
Structured  CAN
Unstructured  Gnutella
Hybrid  JXTA
Applications outside Computer
Science
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Bioinformatics
Education and academic
Military
Business
Television
Telecommunication
Why Peer-to-Peer Networking?
• The Internet has three valuable fundamental assetsinformation, bandwidth, and computing resources - all of
which are vastly under utilized, partly due to the
traditional client-server computing model.
• Information - Hard to find, impossible to catalog and
index
• Bandwidth - Hot links get hotter, cold ones stay cold
• Computing resources - Heavily loaded nodes get
overloaded, idle nodes remain idle
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Benefits from P2P
• Theory
• Dynamic discovery of information
• Better utilization of bandwidth, processor, storage, and other
resources
• Each user contributes resources to network
• Practice examples
• Sharing browser cache over 100Mbps lines
• Disk mirroring using spare capacity
• Deep search beyond the web
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CLIENT / SERVER SYSTEM
CLIENT / SERVER SYSTEM
What Is a Client/Server system?
• A system that links a client and server through networks.
• It describes a computing model for the development of
computerized systems.
• This model is based on the distribution of functions
between two types of independent and autonomous
processes; servers and clients.
Client / Server System
Network
Server process
Services: File, print, fax, multimedia,
communications
Client process
Clients request services from different
server processes.
Clients can request services from several servers and servers
can provide services for more than one clients.
Forces that drive the trend to
Client/Server Systems
• The changing business environment.
• The growing need for enterprise data access.
• The demand for end user productivity gains based on the
efficient use of data resources.
• Technological advances that have made clients/server
computing practical.
• Growing cost/performance advantages of PC-based
platforms.
• Cost / Performance advantages of the PC-based platform
Driving forces
• Technological Advances
-Microprocessor Technology: New microprocessors are capable
to, or even better than, that of many mainframes and
minicomputer systems. Such processing power makes it possible
to dedicate PCs to tasks that used to be delegated to
mainframes and minicomputers.
- Data Communications and Internet: Advances in data
communication and the Internet have allowed the integration of
PCs with the existing networks of minicomputers and
mainframes.
Driving forces -cont.
• Operating Systems and Graphical User Interfaces (GUI)
• The GUI made it possible for end users to put this power to
work, thus making the GUI a major contributing factor to the
PC’s success in the workplace.The GUI has made it possible for
end users to create many of their own applications, thus
making them more autonomous.
• Ex) Microsoft Windows, Apple’s Macintosh, IBM’s OS/2
Client/Server Architecture
• The client/Server architecture is based upon hardware and
software components that interact to form a system.
• Front-end application(Client): Any computer process that
requests services from the server.
• Back-end application(Server): Any computer processing
providing services to the clients.
• Communications middleware(Middleware): Any computer
process through which clients and servers communicate.
How components interact?
SQL
SQL
Client
process
Data
Clients process sends SQL
request through
communications
middleware.
Communications
middleware
network
Database
server
Data
Middleware routes SQL request
to database server process.
Database server
process receives
request, validates it,
and executes it.
Server components
• Database services: When server receives the SQL codes, it
validates it, executes it, and sends only the results to the
client.
• The computer that houses the server process should be a
more powerful computer than the average client computer
because it must be able to handle multiple requests from
multiple clients.
• Minimum requirements
-Fast CPU (RISC, Pentium, PowerPC)
-Fault-tolerant capability
-Expendability of CPU
-Multiple communications options