CE52102-2 Client Server Systems

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CE52102-2Client Server Systems

• Lecture 1
• Introduction and Course Overview
• Introduction to module and Assessment
• CISCO 2
• Lecture CSS architectures
• Summary

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Introduction

• Module Staff
• Consolee Mbarushimana
• Email c.mbarushimana_at_staffs.ac.uk
• Tel [phone]
• Room - B178
• Learning Outcomes
• Demonstrate knowledge and understanding of
  current client server system technologies for
  application across internet/intranet
• Ability to compare and analyse different network
  models
• Ability to develop an appropriate client server
  solution
• Evaluate a client server solution using
  appropriate criteria
• So
• Designing networks
• Building servers

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How the module will work

• 1 lecture per week
• tutorial 2 hours per week
• First hour
• Tutorial and practical work
• Second Hour
• Continuing with work from first hour
• Individual feedback on assignment progress
• Working on assignment
• Working on CCNA 2 material
• Research on allocated topics

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Module Assessment.

• The assessment for this module is split.
• Assignment 50
• Working in Groups
• Staged assessment
• Stage 1 Presentation week 5
• Stage 2 Report detailing recommendations and
  design
• Stage 3 Practical set up of part of recommended
  network design.
• Exam 50
• Taken in summer assessment period April/May
• More details later in course

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CCNA-2 Routing Protocols and Concepts

• You can register for Cisco certification 2
  (CCNA2)
• Similar to work you did on CCNA1 in CE52014-2
  Networked Computer Systems i.e.
• you will need to do a weekly test via Cisco
  Academy website
• Also a separate practical end test.
• The weekly tests do not form part of the module
  assessment but will give you tremendous help on
  the assignment.

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Application Layer - Introduction
Application Layer
Applications (e.g., email, web, word processing)
Transport Layer
Network Layer

• Application architecture
• The way in which the functions of the application
  layer software are spread among the clients and
  servers on the network

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Logical Architecture

• P-A-D architecture
• Presentation user interface
• Application application logic or processing
• Presentation logic part of the application
  program responsible for interfacing to the user
  interface
• Business logic the actual program rules of the
  program responsible for controlling program
  execution and enforcing business rules
• Database logic part of the application
  responsible for interfacing to the database
  management system
• Data - data management or data manipulation

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Clients and Servers

• Servers
• - Mainframe
• - Microcomputer
• Cluster
• Virtual Server

• Clients
• - Microcomputer
• - Terminal
• - Network computer
• - Transaction terminal
• - Handheld

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Application Architectures

• Determined by how functions of application
  programs are spread among clients and servers
• Host-based Architectures
• Server performs almost all functions
• Client-based architectures
• Client performs most functions
• Client-server architectures
• Functions shared between client and server

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So what is a client/server?

• Information systems are constructed according to
  a distributed architecture paradigm, where the
  overall information systems duties are shared
  between client and server computers
• We can connect computers together in various
  ways.
• In a client server system one computer makes a
  request the other provides the response
• This development has revolutionized computer
  networks
• The Internet relies heavily upon the client
  server model

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Figure 1-21 Client/Server versus
Mainframe-Terminal Architectures
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Mainframe and Dumb Terminals

• Client captures key strokes then sends them to
  the mainframe
• Client displays information according to the
  servers instructions

• Not user friendly
• Host becoming a bottleneck
• Host upgrades typically expensive and lumpy
• Inflexible

• Easy to maintain
• Secure

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So what is a client/server?

• How is client/server different from other
  distributed computing?
• Heavy reliance on user-friendly applications
• Emphasis on centralizing databases and management
  functions
• Commitment to openness/modularity
• Networking fundamental to operation

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Generic Client/Server Architecture
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2-tier and 3-tier Architectures

• Two-tiered client/server architectures deliver
• the presentation logic on the client
• and the database logic on the server.
• The business logic may be distributed
• on the client (fat client)
• or the server (fat server)
• Three-tiered client/server architectures deliver
• the presentation logic on the client,
• the business logic on a dedicated server of its
  own, and
• the database logic on a super-server or mainframe

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Figure 1-24 Two-Tiered versus Three-Tiered
Client/Server Architecture
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Workstations and File Server

• Inefficient file access
• Network congestion
• Requires heavy duty client

• Ability to share data
• Ability to share programs

• File Server
• A high-capacity disk storage computer that each
  computer on a network can access and retrieve
  files from.
• Entire files are transferred from the server to
  the client for processing.

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Database Server Architecture
Database

• Less network traffic
• Distributed processing over clients
• Optimised database access

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Three-tier Architecture
Database
Application server
Database server

• Separates applications and databases for load
  balancing
• Prevents one resource from being overwhelmed
• Easy to upgrade and replace tier

• Cost
• Increased complexity

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Peer to Peer Architecture

• All computers can serve as a client and a server
• Increased popularity in the last decade due to
  the rise of P2P services such as Napster
• Advantages
• Data can be stored anywhere on the network
• Very resilient to failure
• Disadvantages
• Finding data
• Security

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Criteria for Choosing Architecture

• Infrastructure Cost
• Cost of servers, clients, and circuits
• Mainframes very expensive terminals, PCs
  inexpensive
• Development Cost
• Mainly cost of software development
• Software expensive to develop off-the-shelf
  software inexpensive
• Scalability
• Ability to increase (or decrease) in computing
  capacity as network demand changes
• Mainframes not scalable PCs highly scalable

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What is happening in business?

• A review of requirements
• Matching business needs to technical
  infrastructure

Figure 1-3 The Top-Down Model
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The top-down model

• The top-down model is a structured methodology
  followed in order to assure that the implemented
  network (solutions) meet the communication needs
  of the intended business, organization or
  individual (requirements)
• It is important to use the top-down approach to
  network analysis and design to assure that the
  network design implemented will meet the business
  needs and objectives which motivated the design
  in the first place

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Business Process Re-engineering

• BPR is when businesses re-examine their business
  processes
• The top-down model provides a structured
  methodology in which to complete this
  re-examination to ensure that the business level
  requirements are met by the lower layers of the
  top-down model

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Downsizing, Rightsizing, Upsizing, and
Smartsizing
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Transparency, scalability and portability

• Attributes of distributed processing
• Transparency refers to
• the ability of distributed processing systems to
  combine clients and servers of different
  operating systems, network operating systems, and
  protocols, into a cohesive system, processing
  distributed applications without regard to the
  aforementioned differences.
• Scalability refers to
• the ability of distributed processing systems to
  add clients without degrading the overall
  performance of the system.
• Portability refers to
• the ability for client/server applications to be
  developed in one computing environment and
  deployed in others

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Figure 1-15a Key Attributes of Distributed
Processing
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Figure 1-15b Key Attributes of Distributed
Processing
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Figure 1-17 Key Components of Database
Distribution
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Client/Server Architecture

• Cost-Benefit Issues
• Client/server systems enable the firm to scale
  the system in a rapidly changing environment
• Client/server computing also allows companies to
  transfer applications from expensive mainframes
  to less expensive client platforms
• Client/server systems reduce network load and
  improve response times

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Summary

• We have discussed the introduction of this module
• This has been an introduction to Client/Server
  Systems
• We have discussed the current thinking in this
  area