an introduction to client/server architecture dr. farid farahmand
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An Introduction to Client/Server Architecture
Dr. Farid Farahmand
A Brief History: Open Platform
The good old days Octopus-like mainframes Only a few venders to choose from Farms of disks where required Applications were specific for each machine
Open platform New client/server architecture Open system allowed mix-and-match
Different application technologies could be purchased from different venders
Examples: server platform, client platform, network protocols, middleware software, etc.
What is Client/Server (C/S) Computing It started as PCs became more powerful
PCs were no longer dumb terminals Provided an open and flexible environment C/S is considered as a form of distributed
software
Distinct characteristics of C/S Client-server is a computing architecture which separates a client from a
server It is almost always implemented over a computer network The most basic type of client-server architecture employs only two
types of nodes: clients and servers. This type of architecture is sometimes referred to as two-tier. It allows devices to share files and resources.
Server provides the service Client is considered as the customer requesting the service The server service can be shared among a number of clients Clients must request or initiate the service The location of the server in the network is transparent to clients Transaction between C/S is message-passing based C/S architecture is scalable
horizontally (more clients can added) Vertically (more servers can be added)
The server is centrally maintained where as clients are independent of each other
Systems with C/S Architecture File servers
File sharing and file processing Data base servers
Passing file results Example: Query in DBMS server Typically one single request/reply
Transaction servers Transaction server includes DBMS and transaction monitoring Server has remote procedures run online by the client
web servers Super-fat servers and thin clients Uses HTTP protocol Java was first to introduce interactive C/S forms
Client
Client
Server
Server
Internet
Client JAVA
ClientHTML
Application
Client/Server Models Where to push the application to Fat clients
The bulk of the application is running on the client The client knows how the data is organized and where it is Different clients access the same applications different ways
Fat servers The server more complicated The clients are less complex More of the code runs on the server The network interaction is minimized
ServerClient
Application
Middleware Software It is the (/) between client and server which glues them together
Allowing the client request for a service and the server providing it
Middleware can also be between server/server Two broad classes
General LAN servers, TCP/IP, Communication stacks, Queuing services,
etc. Application specific
Used to accomplish a specific task Groupware specific: SMTP Internet specific: HTTP Database specific: SQL
Two-Tier vs. Three-Tier Architecture
Same basic idea as fat-client versus fat-server Depends on how the application is divided between the server
and the client Two-tier servers
Examples: file servers and database server In this case the process (application logic) is buried within
the client or server (or both) Three-tier servers
Examples: Web and distributed objects In this case the process is run on the middle-tier –
separated from the user and data interface They can integrate the data from multiple sources More robust and more scalable
Client/Server Building Blocks
Purpose How to divide the application
between the client and server What are different
functionalities of client and server
Basic client server model Fits various applications
Small office Small business Enterprise Global
Client
Server
Server
Client ServerMiddleware
Single Machine
Client Server
Middleware
Client Middleware
C/SMiddleware
C/S
C/S
C/S
Servers and Client Building Blocks
Web Browser GUI DSM OS
Service-Specific; DSM NOS (securit, peer-to-peer, directory, distributed files);
Transport stack (TCP/IP)
Web serverGroupware
DMBSEtc.
ClientMiddleware
Server
NOS=Network operating system
Server Scalability
PC Server
Asymmetric Multi-processing Superserver
symmetric Multi-processing Superserver
Multiservers
Server Scalability Superserver
A very powerful server Single-server or multiserver Each server can have a single processor or multiprocessor Multiprocessing can be Asymmetric or Symmetric
Multiprocessing Asymmetric: each processor is dedicated to a specific task Fully symmetric (SMP): applications are divided into threads and threads are sent to available
processors Examples: 32-bit NT, Unix, NetWare Requires 3 basic functionalities:
Global scheduling I/O sharing structure OS access sharing
Multiservers Pool of servers, providing more processing power (also called a cluster) They divide the task between different servers
Server lite As opposed to full blown servers Provides a background process on the client machine that can accept unsolicited networks
request (refreshing database, synchronizing time, etc.)
OS Wars General trends
More powerful PCs (fat PCs, Network PCs, Multimedia PCs) Operating system applications
Embedded devices (cell phones) Clients Super clients Servers SMP servers Clusters
OS players DOS and Windows 3.x/95 JAVA OS OS/2 Wrap NT/XP/2000/2003/VISTA NetWare (Novell’s, poor application server, fast file server) Unix Linux Specialized parallel OS for clusters
Client/Server Networking Model
Networking in Linux follows the client/server model Server provides the resource (web server) Client talks to the server (browser, e-mail program)
Server has a corresponding program that communicates with the client (runs in the background) In Windows the server program called service In Linux the server program called daemon in Linux
UNIX/Linux
UNIX was introduced in 1969 Linux is from the early 1990s
Based on MINIX Three basic components
Kernel – central portion of OS File system – provides input and output
mechanisms Shell – provides user interface
Linux Introduction
Source code is freely available Developers can make changes
Available from a number of organizations (called disro) Red Hat Mandrake SuSe
Linux Resource
List of Linux compatible hardware: http://www.linuxquestions.org/hcl/
List of hardware issues and forums for Linux http://www.linuxcompatible.org/
Third-party utilities allowing Windows to read the drives of a Linux installation on the same machine http://pro.mount-everything.com/ http://www.symantec.com/home_homeoffice/products/
overview.jsp?pcid=sp&pvid=pm80
Fedora Linux Two ways to obtain
Installation CD Download and burn your own CD – Read to see how to burn a DVD
http://fedoraproject.org/wiki/Distribution/Download Obtain a copy
http://download.fedora.redhat.com/pub/fedora/linux/core/6/i386/iso/ http://download.fedora.redhat.com/pub/fedora/linux/core/4/i386/iso/
Fedora core 6, i386 Intel x86 processor compatible, first CD – ISO image FC-6-i386-disc1.iso
When you have dowloaded the ISO images, you need to burn them on CD/DVD Popular Windows CD burning tools: http://iso.snoekonline.com/iso.htm You can also use CD BurnerXP Pro http://www.cdburnerxp.se/
Summary
Got it?
Homework 1 – LinuxMonday
Visit Fedora Core Web cite. What is the latest version of Fedora?
Burn a copy of Fedora Core 4 on CDs or DVD. You must have this in order to install Linux on your machine – You are not allowed to do the lab without your own CD.
Search for Linux Commands and obtain a one or two-page long list of some of Linux commands used with Fedora Core 4 version
In your own words, list 5-10 differences between Fedora Core 4 and Fedora Core 7 version. You must tabulate your answer.
Do a little research and briefly explain the sequence involved in installing Windows and Linux. What will you do if Windows is already installed?
NOTE: Submit a hardcopy only.
references
http://www.nakov.com/inetjava/lectures/part-1-sockets/InetJava-1.1-Networking-Basics.html
http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2011.htm on ISDN Learn about 2-Tier and 3-Tier systems:
http://www.sei.cmu.edu/str/descriptions/clientserver_body.html
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