Network Technology Notes PDF

NETWORK TECHNOLOGY Data communication is the transmission of data from one location to another for direct use or further processing. It can also be simply defined as the transmission of data and information between two or more computers. A data communication system is made up of hardware, software...

NETWORK TECHNOLOGY Data communication is the transmission of data from one location to another for direct use or further processing. It can also be simply defined as the transmission of data and information between two or more computers. A data communication system is made up of hardware, software and other communication services. Communication can be set up to serve a small area of persons (locally) or a wide area of persons (globally). In order to transmit data, communication channels are used to carry the data from one location to another across a network. The channels are categorised based on their bandwidth. Bandwidth determines the volume/amount of data that can be transmitted in a given time. Therefore, the wider the bandwidth the more data can be transmitted in a given time. A network is a group/set of computers linked to share resources such as data, information, software and hardware (peripheral devices). It enables easy communication among users. Some terms to note:  Communication channel – is the method used for transmitting data across a network  Transmission rate – the speed at which how fast data is transferred  Bandwidth – the amount of data that the channel can handle at any one given time  Upload – sending information from your computer to another in a network  Download – receiving information on your computer from another in a network  Network Topology – is the arrangement of the elements within the structure of a communication network  Telecommunications link – this is one type of information transmission path to connect two points on earth Categories of networks  Local Area Networks (LANs) – consists of a collection of computers (usually within an office building, department or school) that can share devices, files and programs and communicate with each other on the network. A LAN is a network linking computers across a small geographical area. Examples of this would be a hospital, school or small community  Metropolitan Area Network (MANs) – falls between a WAN and LAN, it is large enough to cover an area like a city or campus and may be owned by and operated by a single organisation. (e.g. a college or university)  Wide Area Networks (WANs) – this type of network connects mainframes, LAN’s and Personal Computers (PCs) across a large geographical area (e.g. city, country, state). A WAN is a network linking computers across a large geographical area. An example of this would be the internet. Network devices  Modem (modulator/demodulator) – device used to convert analogue signals to digital and vice versa  Router – controlling the travelling paths of packets from the source to its destination and providing alternate paths when necessary  Switch – a hardware device that filters and forwards packets through the network. It connects devices on a computer network to receive and forward data to the destination.  Hub – hardware device that enables interconnection of multiple devices on a network.  Network interface card (NIC) - handles the translation of digital information into electrical signals for outgoing network communications and translates incoming signals into their digital equivalent for delivery to the machine where it is installed. N.B. – Access Point is a device attached to the LAN and contains a radio transmitter/receiver that translates computer signals into wireless signals and broadcast to NICs Transmission media can be divided into two (2) main categories: 1) Wired/Cabled 2) Wireless Wired/Cabled Media Wired/Cabled media use three (3) types of cables to connect computers which are as follows:  Twisted Pair – A type of cable that consists of two independently insulated copper wires twisted around one another.   Coaxial – A type of wire that consists of a center wire surrounded by insulation and then a grounded shield of braided wire. The shield minimizes electrical and radio frequency interference.  Fibre-Optics – A type of cabling that consists of a center glass core surrounded by several layers of protective materials. It uses pulses of light sent along a light conducting fibre to transfer information from sender to receiver. Advantages Disadvantages Relatively inexpensive Limited bandwidth Twisted Pair Susceptible to electromagnetic interference Easy to work with (to add computers/devices) and cross-talk Easily tapped/ susceptible to eavesdropping Durable Relatively low bandwidth Coaxial Cable Relatively immune to electromagnetic interference (EMI) Transmits voice and data Cost more than twisted pair Inexpensive and easy to install Carry signals over long distances Is immune to electrical interference Optical fibers are expensive Fibre-Optic Is not affected by weather Can transmit over very long distances Installation/maintenance ― any crack in the core will degrade the signal, and Transmits information at great speeds all connections must be perfectly Is more secure than other channels aligned Used for many video Wireless Media Wireless media are not physically connected to each other and some of these are as follows:  Radio waves is a wireless transmission medium that carries data via radio frequency signals. E.g. FM, AM, Cordless phones and televisions  Microwaves are high-frequency radio waves and infrared frequencies to provide broadband connections that can send and receive voice, video and data information over the airwaves.  Satellites are microwave relay stations suspended in space. Satellites use microwave signals to transmit data to and from earth-based microwave relay stations. These are used in weather reports and Satellite-based Global Position System (GPS) which is used to guide vehicles to various destinations and to keep track/monitor just about anything  Infrared is a wireless transmission medium that carries data via light beams. Transmitter and receiver must be in line of sight. The remote controls used on televisions, VCRs, and stereos are examples of infrared. Network Configurations These configurations include nodes which are devices or points on a large network. Nodes can be devices such a PC, phone, or printer that are connected on a network There are three (3) main types of network configuration which are:  Bus / Line Networks – All nodes are connected to a single central cable.  Star Networks – Devices connected to a central server or hub  Ring Network – Each node is exactly connected to two other nodes, forward and backward, thus forming a single continuous path for signal transmission (token ring) Bus/Line Topology Advantages of Bus/Line Topology  Inexpensive and easy to install  Add/remove devices at any point without affecting rest of the network  Simple and reliable  Failure of one device usually does not affect the rest of the network  Cabling Easy to expand/extend Disadvantages of Bus/Line Topology  A break in main cable or lack of terminator will affect the network  Terminators required at both ends  Difficult to identify problems  Heavy transmission slows down the network Star Topology Advantages of Star Topology  Easy to add/remove devices without disrupting network  Easy to administer and manage the network  Failure of one device (other than the central hub) does not affect the rest of the network  Easy to detect faults Disadvantages of Star Topology  If the central server (hub) fails, the entire network is affected  Uses more cable compared to other topologies  More expensive than Bus topology because of connecting devices Ring Topology Advantages of Star Topology  Token passing makes ring topology perform better under heavy traffic  Equal access to the resources  Reduced chances of data collision Disadvantages of Star Topology  Failure of one computer can affect the network  Data packet must pass through all the nodes  Security may be an issue since data must pass through all nodes Transmission Protocols Protocols are rules which govern the transmission of data across a channel or network  In a simplex channel, information can only travel in one direction. It is a send-only or receive-only line. Radio/Television  In a half-duplex channel, information can travel in both directions, but only one at a time. Data can be either sent or received at any given time. Walkie-Talkie, CB Radio  In a full duplex channel, information can travel in both directions, at the same time. data can be both sent and received at the same time. Telephone