Data Communication and Networking Basics Tutorial -A Beginner's Guide to Network-Tele-commmunications Engineering FAQs
Tutorial on Network
Sharing information is the purpose of communication engineering and the sharing is done through signals. This sharing can be local or remote. When two person, in the same place or room, try to communicate, each of them can hear the sound signals because their signals need to pass only a small distance. as signals starts traveling far away from its source, it starts to lose its energy, which make signals weak and the receiver can not detect the signal properly. In case of remote communications such as city to city, country to country , or any inter-planetary communications, the signals need to be carried in such a way so that it does not lost its strength and it need to remain detectable and intelligible to the receivers. No matter how you are communicating with each other, every communication need to generate signals in order to carry the information which can be human voice, computer data, video call, videos etc. The basic components necessary to design a communication system is the same regardless of if you are in a space shuttle or in your home. The main components are transmitter, receiver & antenna and every communication device must have all these three components. When you say something or voice need to be converted into signals or more specifically radio signal which is done by the transmitter and is passes through the media and at the end reaches at the receiver end of the person you are trying to communicate. In case of mobile communication the media can be air (wireless) and in case of Public phone it can be a cables. While your voice or data signal pass through the media(wire, air) with the speed of light(300,000 kilometers per second) get corrupted due to the resistance of the media or path. Most common resistance known are interference, noise, fading.
It's just a natural phenomena that the speed of electromagnetic radiation moving through empty space always has the same value.
The frequency, "f," is the number of completed periods in one second. If the period is 1/2 second, the frequency will be two wavelengths per second (1/2 second for one wavelength, so two wavelengths in one second). In general,
The speed of the wave is equal to the wavelength times the frequency.
What is analogue signals
A variety of signals and wavelengths that can be transmitted over communications lines such as the sound of a voice over the phone line. These signals are in contrast with digital signals.
A continuously varying signal or entity.
A continuous wave form that changes smoothly over the time.
Data that are continuous and smooth and not restricted to a specific values like digital data.
A signal that does not exhibit the same pattern after a specific interval of time or period.
When a signal travel through a medium like wire(copper ,optical fiber) or wireless(air) it losses energy due to the resistance of the medium.
What is Bandwidth?
The difference between the highest and the lowest frequencies of a composite signal.It also used as a means of measuring the information carrying capacity of a line or a network.
What is Backbone?
The major or the main transmission path in a communication network. In fact users at first access the access link (modem,wireless access point,LAN cable for Internet) of a network.In the second stage users data enter the distribution network(can be high performance LAN switch) and at last the backbone link which is connected to the main Internet Router.
A browser is an application program which displays a www document on computer screen. Example : Internet explorer, Mozilla Firefox.
What is baud rate?
A term used to measure the speed of an analogue transmission from one point to another. Although not technically accurate, baud rate is commonly used to mean bit rate.
This refers to the number of binary digits, or bits, transmitted per second (bps). It is also referred to as transmission rate. Communications channels using telephone channel modems are established at set bit rates, commonly 2400, 4800, 9600, 14,400, 28,800 and higher, e.g. when using the Public Switched Telephone Network (PSTN).
bits per second (BPS)
This is the bits (binary digits) per second rate. Thousands of bits per second are expressed as kilobits per second or kbps.
binary digit (bit)
A 0 or 1, which reflects the use of the binary numbering system. It is used because the computer recognises either of two states, OFF or ON. The shortened form of binary digit is bit.
It’s a technology where a signal can share the bandwidth of a medium like LAN connection.
A group of binary digits stored and operated upon as a unit. In user documentation, the term usually refers to 8-bit units or characters. One kilobyte (KB) is equal to 1,024 bytes or characters; 640 KB indicates 655,360 bytes or characters
In this technology, TV cables can be used for both the Internet and cable access.
A tone signifying a connection the modem can alter to communicate data across telephone lines.
What is a composite signal?
Any periodic signal can be decomposed in a collection of a sine waves, each having a measurable amplitude, frequency and phase. A composite signal can be decomposed by Fourier analysis. If you generate any sound using any synthesizer then that sound can be decomposed into its component signals which are basically sine waves. So, we can call any signal is a combination of a number of sine waves each having its different frequencies. In reality we can generate any man’s voice using Fourier analysis.
When a network faces excessive traffic or transfer of data causing a degradation of the network service like lower bandwidth per user.
What is crosstalk?
Usually noise on a line caused by signals traveling along another line.
A cycle is a repetitive unit of a period signal.
Data communications definition
A type of communications in which computers are able to exchange data over an electronic medium.
what is digital signal?
Signals that are discrete and uniform. In this manual, the term refers to the binary digits 0 and 1.These signals are in contrast with analogue signals.
DHCP(dynamic host configuration protocol)
It’s a protocol which assigns dynamic IP to every computer when it joins a network.
Duplex indicates a communications channel capable of carrying signals in both directions.
Domain name system(DNS)
A TCP/IP application service that converts user friendly name( for example www.yahoo.com)
into a IP address(for example 220.127.116.11)
DSL(digital subscriber line)
It’s a technology which uses existing telephone network (landphone) to offer the service of delivering data, voice, video, and multimedia.
Any noise in the transmission line(LAN Cables, copper wires) can corrupt the data.It can be created by electric motors, generators, transmitters, and so on.
These signals will flow in both directions at the same time. In microcomputer communications, may refer to the suppression of the on-line local echo. Telephonic conversion is an example of full duplex communication.
These signals will flow in both directions, but only one way at a time. In microcomputer communications, may refer to activation of the online local echo, which causes the modem to send a copy of the transmitted data to the screen of the sending computer.Exaple-walkie-talkie.
HTML(Hyper Text Markup Language)
The computer language for specifying the contents and format of a web page. It allows the web designer to include codes that define the fonts, layouts, embedded graphics, and hypertext links to a web page.
HTTP(Hyper Text Transfer Protocol)
An application program for retrieving a web document. When we type www.yahoo.com , http:// bring the yahoo main page from yahoo server.
Hertz is a frequency measurement unit used internationally to indicate one cycle per second.
A device that transmits/receives computer data through a communications channel such as radio or telephone lines. It also changes signals received from the phone line back to digital signals before passing them to the receiving computer.
A method of signaling in which both control and user data share the same communication channel.
Electromagnetic waves with frequencies just below the visible spectrum.
ISDN(Integrated services digital networks)
An ITU-T standard for an end-to-end global digital communication system providing fully integrated digital services.
International Telecommunication Union-Telecommunication Standardization Sector.
internet (small i )
A collection of networks connected by interconnecting devices such as routers or gateways.
It is mainly related to an organization’s own networks.
Internet (Capital I)
A global internet that uses the TCP/IP protocol suite for global access of all the computers
connected to the Internet.
Internet address(IP address)
A 32 bit (IPv4) or 128 bit(IPv6) network layer address used to uniquely define a host computer or any networking device such as routers on an internet using TCP/IP protocol.
ICMP(internet control message protocol)
A protocol in the TCP/IP protocol suite that handles error and control messages. Example-ping command is used to test the connectivity of a link. The command is : ping www.yahoo.com.
IGMP( internet group message protocol)
A Protocol in the TCP/IP protocol suite that handles multicasting of messages among internetworking devices or nodes.
Connecting several networks together using internetworking devices such as routers and gateways.
LAN(Local area network)
A network connecting devices inside a single building or inside buildings close to each other.
An acronym for Light Amplification by Stimulated Emission of Radiation. A pure and narrow light beam that can be used as the light source in fiber optic transmission.
The physical communication pathways that transfers data from one device to another.
MAN(Metropolitan area network)
A network which can span a geographical area the size of a city.
It’s a device having the function of both a modulator and a demodulator. It converts a digital signal(which is from computer) into an analog signal. This conversion is known as modulation
which enables the digital to become an analog signal so as it can pass through an analog line(PSTN line).When the analog signal reaches the other end of the receiver’s side then another modem converts the analog signal into digital signal and sends it to the computer-this process is known as demodulation.
The process of combining signals from multiple sources(users) for transmission across a single data link.
An addressable communication device ( for example a computer, a router) on a network can be called a node. Addressable means it has a address which is its IP address.
A theorem which states that the number of samples needed to adequately represent an analog signal is equal to twice the highest frequency present in the original signal.
An eight bit unit.8 bits can be called an octet.
Synonym for data unit: most used in network layer of the TCP/IP model.
A system of rules and procedures governing communications between two or more devices.Protocols vary, but communicating devices must follow the same protocol in order to exchange data. The format of the data, readiness to receive or send, error detection and error correction are some of the operations that may be defined in protocols.
A device that extends the distance a signal can travel by regenerating the signal.
An interconnecting device operating at the first three layers of the OSI models or TCP/IP model. A router is attached to two or more networks and forwards packets from one network to another.Usually a router works with IP address, it forwards packets to its destination based of its IP address.
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The consecutive flow of data in a single channel. Compare to parallel transmissions where data flows simultaneously in multiple channels.
The theoretical highest data rate for a channel.
Electromagnetic wave propagated along a transmission line.
SDH(Synchronous digital hierarchy)
The ITU-T equivalent of SONET.
SMTP(simple mail transfer protocol)
The TCP/IP protocol which defines electronic mail service on the internet. When someone writes
an email it is transferred to the sender by SMTP protocol.
SNMP(Simple network management protocol)
The TCP/IP protocol that specifies the process of management in the Internet.
SONET(Synchronous optical network)
A standard developed by ANSI for fiber optic technology that can transmit high speed data.It can be used to deliver text, audio, and video.
A type of electromagnetic signal propagation that can penetrate the ionosphere. Its happens
when space shuttle in space communicate with planet earth.
The range of frequencies found in a signal.
The further division of a network into smaller networks.
A device multiple communication line or networks together.
A 1.544 Mbps digital transmission line which have 24 communication channel each having
64 Kbps bandwidth.
TCP/IP( Transmission control protocol/Internetworking Protocol)
A five layer protocol suite that defines the exchange of transmission of data across the Internet. All communications in the Internet are controlled by TCP/IP protocol.
A company (formerly Bellcore) involved in the research and development of telecommunication technology.
The amount of actual user data transmitted per second without the overhead of protocol
information such as start/stop bits or frame headers and trailers. Compare it with characters per second.
Transmission from an earth station to a satellite.
Sending a local file or data to a remote site.
ITU-T standards that define data transmission over telephone lines.
What is VPN (Virtual Private Network)
A private network can provide privacy to an organization when sending information among different cities or countries offices of that organization. But establishing a dedicated link between different office among the cities or even countries involve lots of cost. This link cost can be minimized if we use the virtual private network technology where we do not need any private link among offices but Internet. VPN creates a network that is private but virtual since it uses the global Internet. It is private because it guarantees privacy inside the organization. It is virtual because it does not use real private WANs; the network is physically public but virtually private due use of security features. Usually VPN technology uses two simultaneous techniques to establish privacy and those two are: encryption/authentication of the data to be sent and creating the tunnel between the receiver and sender.
A DSL based technology for short distances.
Very High Frequency(VHF)
Radio waves in the 30 MHz range using line-of-sight propagation.
Very Low Frequency(VLF)
Radio waves in the 3 KHz to 30 KHz range using surface propagation computer. The connection is made after both the computers do handshaking. After the connection, all packets follow the same route and arrive in sequence.
It’s a logical circuit made between the sending and receiving
The propagation speed of a signal divided by its frequency is wavelength.
Synonym for world wide web(WWW)
It’s a unit of hypertext or hypermedia available on the web.
Wide Area Network
A network that uses a technology that allows users to span their network a large geographical distance. A WAN may consists of a network widespread in many countries. For example, Microsoft has their office in UK,USA, China and many to name. All the Microsoft offices are connected to each other by WAN.
WWW(world wide web)
It’s a multimedia internet service which allows users to search internet by moving from one document to another via links that connect them together.
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