Data Communication and Networks

Data Communication

• Data communication involves transmitting data and information between two or more computers.
• This is used for communication at the workplace (exchanging files and sending information), and accessing the internet.
• This is the process of transmitting data between computers through wired or wireless communication links.
• Uploading sends data from your computer to another, while downloading receives data from another computer to yours.
• Network: Computers connected via communication links to share hardware, data files, and programs.

Network Configurations

• Point-to-Point: A direct link between two computers in a network.
• Broadcast: One computer transmits to serve multiple terminals/computers in a network.

Network Types Based on Geographic Span

• LAN (Local Area Network): A network where computers share devices, information, and communicate within a small area like a building or school.
• MAN (Metropolitan Area Network): Larger than a LAN but smaller than a WAN, typically comprising networked interconnections within a city, offering internet access.
• WAN (Wide Area Network): A network covering a large geographic area like a city, state, or country, transmitting information via high-speed lines, microwave links, or satellites.
  • Internet is a wide area network

Wireless LAN (WLAN)

• A wireless computer network that links two or more devices using wireless communication to form a LAN in an area such as a home or office.
• WLANs enable users to move around within the area while staying connected to the network.

Connecting Computers to a LAN Requires

• Network cabling
• Network cards for each computer
• Hub
• File server
• System software

Hubs

• A hub is a networking device that connects multiple computers and devices.
• Hubs act as a core component, a repeater or concentrator in LANs.
• Devices linked to a hub are on the same subnet and receive all transferred data, which is suitable for smaller networks.
• File Server: A high-performance computer with large capacity hard disk drives available to all network users that contains all applications and data to be shared between network users and is responsible for managing shared files.

Network Topology Types

• Network topology describes how devices are connected in a network.
• Star Network: All devices are connected to a central hub using cables.
  • A cable break won't affect the functioning of the network.
  • However, if the hub breaks, all connected computers are affected
• Bus/Line Network: Every computer is connected to a single cable.
  • If the backbone cable breaks, the network fails.
• Ring Network: Computers are connected to each other in a ring shape with no end.
  • Failure of a single node can cause the entire network to fail.

Modem

• Modem: Allows a stand-alone computer to connect to a WAN via a normal telephone line using dial-up.
• Modems convert digital signals from computers to analog signals for phone lines and vice versa.
• It connects devices connected to a network to the internet
• Acts as signal translator by modulating and demodulating.

Key Differences

• Modem connects a computer or network to the Internet.
• Switch Connects computers within an internal network.
• Router Organizes and routes data on and between networks, connecting a home network to the internet (via a modem) whilst connecting many computers to the same network (via a switch).

Transmission Media and Types

• Transmission media sends data from one device to another with computer cables, telephone lines and microwave signals being examples
• Transmission media fall under two categories: wired and wireless.

Wired Transmission

• Twisted Pair Cables: Wires twisted to reduce interference, suitable for short distances are easy to handle and cheap
• Coaxial Cables: Thickly insulated copper wire capable of transmitting data at high speed that are used for television and video cable.
• Fibre-Optic Cables: Transfers data as light pulses through clear glass. it is used by telecommunication companies, video conferencing and interactive services.

Wireless Technologies

• Microwave Used by telecoms providers for radio transmissions and operates over distances up to 70 km.
• Bluetooth For short-range communication between devices. has a limited range of approximately 10 meters
• Infrared For short-range communication, communications links in urban areas, whilst providing very high bandwidth.
• Satellite - For long-distance communication, satellite television and radio, and GPS, has a very long range: 160–2,000 km

Bandwidth

• Bandwidth determines the volume of data transmitted in a given time, measured in bits per second (bps) and is grouped into three channels:

Bandwidth Channels

• Narrowband: Limited-capacity channel for audible signals(less than 12.5 kHz, mainly used in marine activities, aviation, telecommunications and broadcasting.
• Voiceband: Used for transmitting speech(300 Hz to 3,400 Hz, with limited frequency range and used in telephone service.
• Broadband: Wide bandwidth that can transmit multiple signals simultaneously(256 kbits/s, widely used for internet connectivity for residential homes and businesses.

Transmission Mode Types

• Simplex: Data travels in One direction(Uni-directional) with car stereos and pagers as examples
• Half-duplex: Data travels in both directios and onle one direction at a time whilst transmitting.(Bi-directional) with walkie-talkies and fax machines as examples
• Full duplex: Data travels in both directios simultaneously (Bi-directional)with mobile phones as examples

Intranet, Extranet and Internet

• Internet: A global public network using TCP/IP protocol, where computers are assigned unique IP addresses.
• Intranet: A private network for a single organization, using Internet (TCP/IP) technology, not open to external users.
• Extranet: An intranet selectively opened to specific external entities like customers or suppliers

Intranets and Firewalls

• Intranet consists of LANs and WANs.
• Firewalls prevent external access to an organization's intranet.
• Proxy servers filter information between the internet and the intranet.

Internet

• The modem, router or switch should be connected to telephone line.
• The network interface card (NIC) is to be installed your computer
• Use web browser and email package
• A network service subscription
• A modem (modulator/demodulator) which is provided by the ISP, to convert digital signals to analogue signals between your landline and the Internet.- Router to connect more than one computer to the modem.

Internet Connection Types

• Dial-up: Requires a landline and modem, is the slowest connection and does not allow phone use while online.
• Broadband: Uses ADSL, allows phone use while online, sends more data than is received
• Cable TV: Uses a cable TV modem, sends high data volumes via fibre optic systems
• Wireless (2G, 3G, 4G): slower than Broadband and Cable which is restricted and charged by monthly rates for data used.

Web Technologies

• Protocol: Access the services on the network and the internet.
• TCP/IP: Rules for sending and receiving data over the Internet.
• Function of TCP/IP is, to send the data to other computers on the Internet, ensuring that the data is in the right form.
• Server Computer (Host): The services such as email, news or data to the other computers.
• IP address: The unique address to identify any computer on the internet.
• URL: The address of a site on the Internet, that is know as Uniform Resource Locator

IP addresses

• An IP address can be used to track your Internet Usage
• They have four sets of numbers seperated by a full stop "194. 238. 196. 100"
• To access a site on the internet, you must use its URL

Web Browser

• A program allows users to view and explore the world wide web

Parts of an URL

• http:// tells the web browser that this source can be accessed using the hypertext transfer protocol.
• 'www' tells the browser that this is a web page.
• macmillan-caribbean.com tells the web browser to contact the Macmillan Caribbean web server to obtain this resource. A domain name is label that identifies a network.
• /Products/ describes the directory structure(where the document is stored)
• CAPE-Maths-Unit-1 is the document's name.
• .html indicates that the document was created using the Hypertext Mark-up language.

Websites

• A web-server transmits web pages over the Internet
• Search -engine is a software application that finds websites using
• Software application can then find websites

Internet Usage

• Internet cache is when the web browser stores your browsing data on the hard disk which speeds up the display of websites/pages

Podcasts, Blogs, Vlogs

• Podcast: A file over the internet.(Method of distributing audio files). where podcasting lets you create your own online talk show or radio program with the content of your choice which can be used for trainings, story telling, music or talk shows
• Blog :when the internet users frequently post items such as description of events, pictures of what they are interested in at frequent intervals on their personal website.
• Vlog: when the internet users frequently post video or audio on any subject of interest on their personal website.

Methods of Communication

• Email: Method sending and receiving a message electronically between a sender and receiver that both have an email address that uses the ability to attach Text, Pictures and Videos.

VoIP

• VoIP: Voice over Internet Protocol used to convert the sound of voice into digital form and transmit it over the internet.