Lesson for students of IT: "Network and Communications"

1. Network Topologies

1.1. Ring Topology

1.1.1. On a ring network, a cable forms a closed loop (ring) with all computers and devices arranged along the ring

1.1.2. Data transmitted on a ring in ONE DIRECTION

1.1.3. When a computer send or receive data, it travels to each computer on the ring until it reaches its destination

1.1.4. ADVANTAGES: 1. Require less cable 2. No data collision exist between node

1.1.5. DISADVANTAGES: 1. If one computer or device (node) in the network fails, the entire network stop working 2. There will be a limit on distance between nodes

1.2. Bus Topology

1.2.1. Consists of a single central cable

1.2.2. The network transmits data in BOTH DIRECTIONS and the address of the receiving device is included with the transmission so that the data is routed to the appropriate receiving device

1.2.3. Popular on LANs because it is inexpensive and easy to install

1.2.4. Computers and other devices can be attached and detached at any point on the bus without disturbing the rest of the computer as the transmission simply bypasses the failed device

1.2.5. ADVANTAGES: 1. Network can be extended, by adding new node to the backbone 2. If one node fail, it will not affect the other node 3. No disruptions of network when connecting and removing nodes 4. Require less cable

1.2.6. DISADVANTAGES: 1. If the backbone cable fail, the entire network stop working 2. Terminators are required at both ends of the backbone cables 3. Network speed decrease when number of nodes increase

1.3. Star Topology

1.3.1. All the node connects to a central device, thus forming a star

1.3.2. Hub is a central device that provides common connection point for nodes on the network

1.3.3. Data transmitted in BOTH DIRECTIONS

1.3.4. Easy to install and mantain

1.3.5. Nodes can be added and removed from network

1.3.6. If one node fail, it will not affect the other node

1.3.7. If hub fail, the network will be inoperable. Keep backup hubs in case primary hubs fail.

1.3.8. ADVANTAGES: 1. Easy to expand the network. You only need to add node to the hub 2. If one node fail, it will not affect the entire network 3. Do disruptions to the network when connecting and removing nodes 4. Easy to install and wire

1.3.9. DISADVANTAGES: 1. If the hub fail, the entire network stop working 2. Require more cables 3. Network speed decrease when number of nodes increase

2. Network Communications Technologies

2.1. Internet

2.1.1. A public network

2.1.2. Collection of networks in that links millions of businesses, government agencies, educational institutions and individuals

2.1.3. Used to provide information for public

2.1.4. Loose

2.2. Intranet

2.2.1. A private network within an organisation

2.2.2. Provides information to employees

2.2.2.1. Typical applications include electronic telephone directories, e-mail addresses, employee information, internal job openings etc.

2.2.2.2. Employees find surfing their organisational intranets to be as easy and as intuitive as surfing the internet

2.2.3. Like the public internet, intranet uses browsers, websites and webpages.

2.2.4. Provides e-mail, mailing lists, newsgroup and FTP services accessible only to those within the organisation

2.2.5. High

2.3. Intranet

2.3.1. A private network that connects more than one organisations

2.3.2. Provides information to suppliers, customers and business partner

2.3.3. Purpose: To increase efficiency and reduce costs

2.3.4. Used to access data, check status, place orders and send e-mails

2.3.5. Uses Virtual Private Network (VPN) technology to communicate over the internet more secure

3. Importance and Advantages

3.1. Sharing of devices eg. printer and scanner

3.2. Sharing of program / software

3.3. Sharing of files

3.4. Sharing of data

3.5. Sharing of information

3.6. Sharing of high-speed internet connection

3.7. To access server-centered database

3.8. Better communication using internet services such as e-mail, mailing list and Internet Relay Chat (IRC)

4. Types of Networks

4.1. Local Area Network (LAN)

4.1.1. Connects computers and devices at a limited geographical area such as home and office

4.1.2. Cost of data transmission is less because the transmission medium is owned by a single organisation

4.1.3. Speed of data transmission is fast

4.2. Metropolitan Area Network (MAN)

4.2.1. Connects computers and devices in a metropolitan area such as city or town

4.2.2. A MAN typically includes one or more LAN but covers a smaller geographic area than a WAN

4.2.3. Speed of data transmission is moderate / medium

4.3. Wide Area Network (WAN)

4.3.1. Connects computers and devices in a large geographical area such as a country or world

4.3.2. A WAN can be only one large network or can consist of two or more LANs connected together

4.3.3. The Internet is the world's largest WAN

4.3.4. The cost of data transmission is very high because the transmission mediums used are hired either telephone lines or satellite links

4.3.5. Speed of data transmission is slower than LAN and MAN

5. Network Architecture

5.1. Client / Server

5.1.1. One computer act as a server that provides services and the other computers (client) on the network requests services from the server

5.1.2. CLIENT is a computer that 1. Request services from server computer

5.1.3. SERVER is a computer that 1. Provides services to clients 2. Controls access to resources (hardware, software, data and files) on the network 3. Provides a centralized storage for programs

5.2. Peer-to-Peer

5.2.1. Simple and inexpensive

5.2.2. Typically connects fewer than 10 computers

5.2.3. All computers in the network have equal capabilities to use the resources available on the network

5.2.4. With peer-to-peer networks there is NO SERVER

6. TCP / IP

6.1. Definition

6.1.1. A protocol to facilitate communication over computer network

6.2. Protocol

6.2.1. Set of rules for the exchange of data between a terminal and computer or between two computers.

6.2.2. Think of protocol as a sort of pre-communication agreement about the form in which a message or data is to be sent and receive is to be acknowledged

6.3. Is a short for Transmission Control Protocol / Internet Protocol

6.4. TCP / IP is the network standard, specifically a protocol that defines how messages are routed from one end of a network to the other, ensures the data arrives correctly

7. Definition of COMMUNICATION

7.1. A process in which two or more computer or devices transfer data, instructions and information

8. Definition of COMPUTER NETWORKS

8.1. A collection of computers and devices connected together via communication devices and transmission media

8.1.1. Devices: Printer, etc.

8.1.2. Communication Devices: NIC, HUB, Router

8.1.3. Transmission Media (Physical): Twisted pair cable, Co-axial cable, Fibre optic Transmission Media (Wireless): Infrared, Radio wave, satellite