CIM6400 CTNW Lesson 7 – Introduction to PC Networking & Types of Networks

1. CIM6400 CTNWLesson 7 – Introduction to PC Networking & Types of Networks

2. Introduction to PC Networking

3. Defining a Computer Network • A computer network is defined as having two or more devices (such as workstations, printers, or servers) that are linked together for the purpose of sharing information, resources, or both. • A computer network allows users to communicate with other users on the same network by transmitting data on the cables used to connect them. • Network links are made using copper cables, fiber-optic cables or wireless connections. Wireless connections use radio signals, infrared technology, or satellite transmissions.

4. Defining a Computer Network • A network consists of many overlapping systems, such as cabling, addressing schemes, or applications. • The layers work together to transmit and receive data. • The Open Systems Interconnection (OSI) model divides the functions of the network into seven layers. • Viewing the layers from top to bottom, it presents a service model. • At each layer, the function provided depends on the services of the layer below it.

5. File, Print, and Application Services • Computer networks offer file and print services. • In networks, different computers take on specialized roles or functions. • Once connected, one or more computers in the network can function as network file servers. • The server is a repository for files that can be accessed and shared across the network by many users. • Network file services enable collaboration in the development of documents and projects • Network print services can make a high-speed printer accessible to many users.

6. File, Print, and Application Services • All network operating systems offer file and print services. • Sharing information, collaborating on projects, and providing access to input and output devices are common services of computer networks.

7. Mail Services • E-mail services work like the postal system, with one computer taking on the function of post office. • The user e-mail account operates like a post office box, where mail is held for the user until it is picked up over the network by an e-mail client program running in the user system. • The e-mail is sent from the client computer to the server, which acts as the post office. The server holds the e-mail until the destination client retrieves it. • An e-mail address consists of two parts. The first part is the recipient name and the second part is the domain name. • In addition to e-mail, instant messaging services allow network users to chat without delay (ICQ, AOL Instant Messaging)

8. Directory and Name Services • To enable users and systems on the network to find the services they require, computer networks make use of directories and name services. • The network assigns a name to users, services, and devices so that they can be identified and accessed. • Knowing the name of a service on the network enables users to contact that service without having to know its physical location.

9. Directory and Name Services • Directory and name services make a network easier to use. • After the initial setup of the directory or name service, this translation takes place transparently. • In addition to their ease of use, they also make the network more flexible.

10. The Internet • The Internet is a worldwide public network of networks, interconnecting thousands of smaller networks to form one large “web” of communication. • The Internet functions like a highway to facilitate exchange between geographically separated users, organizations, and branches of companies.

11. The Internet • The phrase “information superhighway” describes the benefit of the Internet to business and private communication. • The Internet breaks down barriers of time and space, enabling the sharing of information around the globe almost instantaneously. • Many private networks, some with thousands of users of their own, connect to the Internet by using the services of Internet Service Providers (ISPs). • These linkages enable long distance access to network services for information and device sharing.

12. Network Administration • The ongoing task of network administration is to maintain and adapt the network to changing conditions. • Network administrator responsibilities include: • Setting up new user accounts and services • Monitoring network performance • Repairing network failures • Enforcing Security

13. Simplex, Half-Duplex, and Full-Duplex Transmission • Simplex transmission is a single one-way baseband transmission. • It is also called unidirectional because the signal travels in only one direction. • An example of simplex transmission is the signal sent from the cable TV station to the home television.

14. Simplex, Half-Duplex, and Full-Duplex Transmission • This means that only one side can transmit at a time. • Two-way radios, such as Citizens Band (CB) and police/emergency communications mobile radios, work with half-duplex transmissions.

15. Simplex, Half-Duplex, and Full-Duplex Transmission • Traffic can travel in both directions at the same time. • A regular telephone conversation is an example of full-duplex communication. Both parties can talk at the same time, and the person talking on the other end can still be heard by the other party while they are talking. • Digital subscriber line (DSL), two-way cable modem, and other broadband technologies operate in full-duplex mode.

16. Types of Networks

17. By using local-area network (LAN) and wide-area network (WAN) technologies, many computers are interconnected to provide services to their users. In providing services, networked computers take on different roles or functions in relation to each other. Some types of applications require computers to function as equal partners. Other types of applications distribute work so that one computer functions to serve a number of others in an unequal relationship. Overview

18. Peer-to-Peer Networks • In a peer-to-peer network, the networked computers act as equal partners, or peers, to each other. • As peers, each computer can take on the client function or the server function alternately. • There is no central point of control or administration in the network. Individual users must back up their own systems to be able to recover from data loss in case of failures.

19. Client/Server Networks • In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients. • The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests. • For better control, the client must identify itself and be authorized (username and password) to use the server resources.

20. Local-Area Networks (LANs) • A local-area network (LAN) can connect many computers in a relatively small geographical area such as a home, an office, or a campus. • It allows users to access high bandwidth media like the Internet and allows users to share devices such as printers.

21. Local-Area Networks (LANs) • The general shape or layout of a LAN is called its topology. • Topology defines the structure of the network. This includes the physical topology which is the actual layout of the wire or media, and the logical topology which is how the media is accessed by the hosts. • The communications channel that they all share is called the medium, and it is typically a cable that carries electrical signals through copper or fiber. • On a LAN, the rules for coordinating the use of the medium are called Media Access Control (MAC).

22. Wide-Area Networks (WANs) • A WAN, as the name implies, is designed to work over a larger area than a LAN. • A WAN uses point-to-point or point to multipoint, serial communications lines. • Point-to-point lines connect only two locations, one on each side of the line. Point-to-multipoint lines connect one location on one side of the line to multiple locations on the other side. • They are called serial lines because the bits of information are transmitted one after another in a series. • Connections across WAN lines may be temporary or permanent.

23. The following are some of the more common WAN technologies: Modems Integrated Services Digital Network (ISDN) Digital subscriber line (DSL) Frame Relay Asynchronous Transfer Mode (ATM) The T (US) and E (Europe) Carrier series (T1, E1, T3, E3, and so on) Synchronous Optical Network (SONET) Wide-area connections make use of the communication facilities that are put in place by utility companies, called common carriers, such as the telephone company. Wide-Area Networks (WANs)

24. Wide-Area Networks (WANs) • Connections across WAN lines may be temporary or permanent. • Telephone or dialup lines, might make a temporary connection to a remote network from a computer in a home or small office. • In both temporary and permanent cases, computers that connect over wide area circuits must use a modem or channel service unit/data service unit (CSU/DSU) at each end of the connection.

25. Wide-Area Networks (WANs) • The public telephone system, sometimes referred to as plain old telephone service (POTS), is a circuit-switched communications network. • When a telephone call is placed in this type of network, only one physical path is used between the telephones for the duration of that call. • This pathway is maintained for the exclusive use of the call, until the connection is ended and the telephone is hung up.

26. Wide-Area Networks (WANs) • In a packet-switched network, each individual packet of data can take a different route and no dedicated pathway or circuit is established.