Chapter 9 Designing a Network 9.1 Network Models Network ModelsNetwork Models 9.2Network Performance Network PerformanceNetwork Performance 9.3Network

Chapter 9 Designing a Chapter 9 Designing a NetworkNetwork

9.1 9.1 Network ModelsNetwork Models

9.29.2 Network PerformanceNetwork Performance

9.39.3 Network PlanNetwork Plan

Chapter 9 Designing a Network

9.1 Network Models

There are two fundamental models of network Peer-to-peer client/server


9.1.1 Peer-to-peer Model

Peer-to-peer network computers communicate with each other as equals Each computer is responsible for

sharing its own resources to others• files, application programs, or devices

– printers, modems …setting up and maintaining its own securityaccessing the network resources it needs

• find out where the resources are,

• what security is required

called workgroup in Windows environment


9.1.1 Peer-to-peer Model


9.1.2 Client/Server Model

Client/server network network resources are

centrally managed by one or more servers.


A. Servers

Server responsible for shared resources

making them availablemanaging themenforcing the security

Dedicated servers are high performance computers with fault-tolerant features


A. Servers

Services include the following: Authentication and security File storage and sharing Printer sharing E-mail services Web hosting Proxy services Application services FTP services Telnet services Dial-in and dial-out services Fax services DHCP services VPN services Video streaming services


A. Servers

Directory service manage the scattered services on a network enables users to browse all the resources easily any changes will update the directories on all servers

e.g. adding a new user, or removing a printer

Chapter 9 Designing a NetworkA. Servers

1. Authentication server

Authentication server also called directory server or domain controller maintains a security database

to keep all the users’ accounts to controls their access level

authenticates users when they log in Member servers

servers other than the authentication server host a service or resource

but do not participate in maintaining the security


2. File server

File server provides a centralised location for storing files with a shared directory or disk drive Security control includes

who can make access to each directory what kinds of access.

locks a shared file which is being editedexcept for a multi-user database


3. Print server

Print server manages one or more printers allows a shared printer to be accessed by authorised users

A shared printer may be connected to a dedicated printer server

a small box with a fixed IP address computer

this requires the computer to be turned on hub

this requires the printer to have a built-in NIC


4. Mail server

Mail server provides e-mail services to users each user has two mailboxes, storing

incoming mails, and copies of sent mails

SMTP serverfor sending outgoing mails

POP3 (IMAP) serverfor storing incoming mails


5. Web server

Web server stores the contents of Web pages

of authorised users

entertains requests from other users on the Internet by delivering the Web pages

The IP address and the URL of a Web server should be made known to DNS servers


6. Proxy server

Proxy server improves the efficiency of Internet access by caching

visited Web pages filters Web pages contents

to prevent users from accessing certain sites.


7. Application server

Application server provides remote computing for clients Typical example: Database server

maintains multi-user databasesruns Database Management System (DBMS)

• to handle data requests from the clients


B. Clients

Client also called workstation in client/server environment a computer that requests services from a server uses a desktop OS with appropriate networking software


9.1.3 Pros/Cons of Peer-to-peer Model

Advantages of Peer-to-peer

1. Less expensive hardware can be used Dedicated servers not required

2. Easy to set up No need to set up servers

3. Expensive OS is not required NOS is more expensive than a desktop OS

4. Smaller chance of failure of the entire network If a server fails, the entire network would fail.


9.1.3 Pros/Cons of Peer-to-peer Model

Disadvantages of Peer-to-peer1. Insecure

desktop OS are not built to be securesecurity is done using password instead of user rights workstations are administered by users

2. Difficult to backup Not easy to backup data in many workstations

3. Difficult to maintain version control Users tend to store documents on a number of different

machines.

4. Difficult to manage users each workstation his its own set of user accounts


9.1.3 Pros/Cons of Client/Server

Advantages of Client/Server 1. Very secure

NOS are designed to be secure servers can be locked physically centrally placed data are easier to manage and track

2. Better workstation performanceDedicated servers handle all the resource sharing tasks

3. Centralised backup Backing up data in a centralised location is easier

4. More reliable servers have fault-tolerant features

5. Easier user managementa single database to keep user accounts

6. Single user logon


9.1.3 Pros/Cons of Client/Server

Disadvantages of Client/Server 1. Require professional administration

to set up and manage.

2. More hardware-intensiveDedicate server is expensive

3. Expensive NOSNOS is more expensive than desktop OS


9.2 Network Performance

The performance of a network refers to efficiency in data transmission the amount of tasks it can handle

Bottleneck reduces network performance part of a network where the capacity cannot meet the

required data flow. caused by

slow servercable of low bandwidthpoor network designadoption of a poor technology


9.2.1 Server performance

A. Efficiency of Hardware number of CPUs and their clock speeds memory size and speed disk drive capacity and speed bus width cache memory size

B. Amount of Services do not overload a server, otherwise bottleneck will occur


9.2.2 Network Traffic and Backbone

Bandwidth maximum rate of data transfer of a network channel To improve the bandwidth, use

full-duplex devices better cable

Network traffic the amount of data flow in each second may also be caused by a hub



Network throughput the amount of actual data flow in each second

a high network traffic may not mean high throughput• e.g. hub-based network.

Backbone of a network the circuit (including a switch and cables) that links up

smaller network segments traffic most busy

Backbone’s bandwidth should be 10 times the segments connected to it

Switches should be used in backboneFiber-optic cable is the best choice




9.2.3 Technology adopted

A. Protocols The protocols not only affect how a network

communicates, but also its performance. should conform with popular standards, like OSI and

IEEE. TCP/IP

breaks message into packetsthe bandwidth of connecting paths can be fully utilised


9.2.3 Technology adopted

B. Topology and hardware Hub-based star topology works well for small networks

only Switched-based star topology is currently the best choice.

C. Network Operating System newer versions are more efficient

always update the NOS patch


9.3 Network Plan

Need Analysis finding out the features that justify setting up a network

improved communicationsimproved information sharing and delivery improved sharing of data across multiple types of computersimproved security and access controls for sensitive dataeasier sharing of job assignmentseasier access to applicationsimproved system managementeasier to perform backups easier to expand


9.3 Network Plan

Design and Cost AssessmentWhat application programs do the system run?How many users are there on the network?How much storage space is required?How much bandwidth is required?What network services are required?What is the budget?Will the plan cater for future expansion?


9.3 Network Plan – A. Smallest network


9.3 Network Plan – B. Home networking


9.3 Network Plan – C. A small office with 15 users

9.3 Network Plan – C. A small office with 15 users


9.3 Network Plan – D. A medium-sized office in 2 floors

9.3 Network Plan – D. A medium-sized office in 2 floors


9.3.4 Documentation

Address List Cable Map Contact List Equipment List Network History Network Map Policies and procedures Server Configuration Software configuration Software Licensing User administration Password List

Documents

Chapter 9 Designing a Network 9.1 Network Models Network ModelsNetwork Models 9.2Network Performance Network PerformanceNetwork Performance 9.3Network