Chapter 9 Designing a Network

1. Chapter 9Designing a Network 9.1 Network Models 9.2 Network Performance 9.3 Network Plan

2. Chapter 9Designing a Network 9.1 Network Models • There are two fundamental models of network • Peer-to-peer • client/server

3. Chapter 9Designing a Network 9.1.1Peer-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 security • accessing the network resources it needs • find out where the resources are, • what security is required • called workgroup in Windows environment

4. Chapter 9Designing a Network 9.1.1Peer-to-peer Model

5. Chapter 9Designing a Network 9.1.2 Client/Server Model • Client/server network • network resources are centrally managed by one or more servers.

6. Chapter 9Designing a Network A.Servers • Server • responsible for shared resources • making them available • managing them • enforcing the security • Dedicated servers are high performance computers with fault-tolerant features

7. Chapter 9Designing a Network A.Servers • Services includethe 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

8. Chapter 9Designing a Network A.Servers • Directory service • manage the scattered services on a network • enables users to browse all the resources easily • any changeswill update the directories on all servers • e.g. adding a new user, or removing a printer

9. Chapter 9Designing a Network A. Servers1.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

10. Chapter 9Designing a Network A. Servers2.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 edited • except for a multi-user database

11. Chapter 9Designing a Network A. Servers3.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

12. Chapter 9Designing a Network A. Servers4. Mail server • Mail server • provides e-mail services to users • each user has two mailboxes, storing • incoming mails, and copies of sent mails • SMTP server • for sending outgoing mails • POP3 (IMAP) server • for storing incoming mails

13. Chapter 9Designing a Network A. Servers5. 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

14. Chapter 9Designing a Network A. Servers6.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.

15. Chapter 9Designing a Network A. Servers7. Application server • Application server • provides remote computing for clients • Typical example: Database server • maintains multi-user databases • runs Database Management System (DBMS) • to handle data requests from the clients

16. Chapter 9Designing a Network 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

17. Chapter 9Designing a Network 9.1.3Pros/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.

18. Chapter 9Designing a Network 9.1.3Pros/Cons of Peer-to-peer Model • Disadvantages of Peer-to-peer 1.Insecure • desktop OSare not built to be secure • security 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

19. Chapter 9Designing a Network 9.1.3Pros/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 performance • Dedicated 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 management • a single database to keep user accounts • 6.Single user logon

20. Chapter 9Designing a Network 9.1.3Pros/Cons of Client/Server • Disadvantages of Client/Server • 1.Require professional administration • to set up and manage. • 2.More hardware-intensive • Dedicate server is expensive • 3.Expensive NOS • NOS is more expensive than desktop OS

21. Chapter 9Designing a Network 9.2Network 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 server • cable of low bandwidth • poor network design • adoption of a poor technology

22. Chapter 9Designing a Network 9.2.1Server 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

23. Chapter 9Designing a Network 9.2.2Network 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

24. Chapter 9Designing a Network 9.2.2Network Traffic and Backbone • 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 backbone • Fiber-optic cable is the best choice

25. Chapter 9Designing a Network 9.2.2Network Traffic and Backbone

26. Chapter 9Designing a Network 9.2.3Technology 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 packets • the bandwidth of connecting paths can be fully utilised

27. Chapter 9Designing a Network 9.2.3Technology 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

28. Chapter 9Designing a Network 9.3Network Plan • Need Analysis • finding out the features that justify setting up a network • improved communications • improved information sharing and delivery • improved sharing of data across multiple types of computers • improved security and access controls for sensitive data • easier sharing of job assignments • easier access to applications • improved system management • easier to perform backups • easier to expand

29. Chapter 9Designing a Network 9.3Network Plan • Design and Cost Assessment • What 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?

30. Chapter 9Designing a Network 9.3Network Plan –A. Smallest network

31. Chapter 9Designing a Network 9.3Network Plan –B. Home networking

32. Chapter 9Designing a Network 9.3Network Plan –C. A small office with 15 users

33. 9.3Network Plan –C. A small office with 15 users

34. Chapter 9Designing a Network 9.3Network Plan –D. A medium-sized office in 2 floors

35. 9.3Network Plan –D. A medium-sized office in 2 floors

36. Chapter 9Designing a Network 9.3.4Documentation • 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