Standard Organization In Data Communication And Networking Pdf

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Standards are necessary in almost every business and public service entity. For example, before , fire hose couplings in the United States were not standard, which meant a fire department in one community could not help in another community. The primary reason for standards is to ensure that hardware and software produced by different vendors can work together.

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What Is a Network Protocol, and How Does It Work?

Chapter 7. Telecommunications, the Internet, and Information System Architecture. The electronic transmission of information over distances, called telecommunications, has become virtually inseparable from computers: Computers and telecommunications create value together. Components of a Telecommunications Network. Telecommunications are the means of electronic transmission of information over distances.

The information may be in the form of voice telephone calls, data, text, images, or video. Today, telecommunications are used to organize more or less remote computer systems into telecommunications networks. These networks themselves are run by computers. A telecommunications network is an arrangement of computing and telecommunications resources for communication of information between distant locations. A telecommunications network includes the following components:.

Terminals for accessing the network. Computers that process information and are interconnected by the network.

Telecommunications links that form a channel through which information is transmitted from a sending device to a receiving device. Telecommunications equipment that facilitates the transmission of information. Telecommunications software that controls message transmission over the network.

Scope of Telecommunications Networks. Two principal types of telecommunications networks can be distinguished from the point of view of their geographical scope. They are:. Local area network LAN : is a privately owned network that interconnects processors, usually microcomputers, within a building or on a campus site that includes several buildings.

Characteristics of a LAN: [Figure 7. LANs are the principal tool of workgroup computing. LANs ensure high-speed communication within a limited area and enables the users to share facilities peripherals connected to it.

Usually include a large-capacity, secondary storage device, where database and applications software are maintained, managed by a microcomputer acting as a file server that delivers data or program files to other computers. Facilities peripherals may include jukebox optical memory and fast printers. Frequently, one of the facilities peripherals in a LAN is the gateway hardware and software that give the network users access to other networks.

More group members may connect to the network from remote sites using wireless telecommunications. LANs are generally composed of a network of microcomputers.

Wide area network WAN : is a telecommunications network that covers a large geographical area. Characteristics of a WAN: [Figure 7. The information system of an entire organization may be structured as a hierarchy.

The WANs system architecture looks very much like an organization chart. WANs connect all the divisional minicomputers to the headquarters mainframe with a variety of local microcomputers and terminals located at remote sites connected, in turn, to the minicomputers.

WANs provide the backbone through which all other nodes computers and terminals communicate. WANs often use telecommunication links and equipment provided by specialized vendors, called common carriers. WANs serve to interconnect multiple LANs and can make specific resources available to a large number of workstations.

Metropolitan Area Networks MAN - are telecommunications networks that interconnect various local area networks within a metropolitan area, that is, within approximately a mile range. Purpose of MANs is to interconnect various LANs within a metropolitan area, that is, within approximately a 50 - mile range.

Interorganizational Information Systems - are shared by two or more companies. Characteristics of Interorganizational Information Systems : [Figure 7. These systems help several firms share information in order to coordinate their work, collaborate on common projects, or sell and buy products and services. Internet has emerged as a global public network of networks. Some interorganizational systems are employed in knowledge work. Can be used to connect a firm's computers to the information systems of its customers, suppliers, and business partners, and are also used to execute business transactions.

Telecommunications links may be implemented with various communication media, with a corresponding variety of characteristics. The main feature of a medium is its potential transmission speed, also known as channel capacity , which for data transmission purposes is expressed in bits per second bps.

An alternative measure of transmission channel capacity is bandwidth - the range of signal frequencies that can be transmitted over the channel. Six potential media are employed to implement telecommunication links:. Terrestrial Microwave. Satellite Transmission. Three of the above transmission media are classified as guided media - in which the signal moves along an enclosed path. Guided media require wiring.

They include:. Three of the above transmission media are classified as wireless media - the signal is broadcast radiated in many directions over the air or space and received through an antenna. Characteristics of Communications Media:.

Twisted Pair a communications medium consisting of a pair of wires. Coaxial Cable a communications medium that consists of a relatively thick central conductor shielded by several layers of insulation and the second conductor just under the cable's shell. Fiber Optics high-capacity communications medium that consists of many strands of pure glass with a data carrying core in the middle, surrounded by a reflective coating and a protective sheath.

Terrestrial Microwave long-distance telecommunications by means of microwave signals travelling on the surface of the earth. Satellite Transmission form of microwave transmission in which the signal is transmitted by an earth station to a satellite which rebroadcasts the signal to the receiving station.

Radio Transmission wireless communications technology that transmits voice or data over the air using a lower frequency band than microwaves. Note: Transmission speeds keep on rising, particularly in the fiber optics area. We are now moving toward a global infrastructure of gigabit-speed fiber optic links relying on digital transmission.

In this multimedia environment, data, text, voice, images, and video will travel at speeds of billions of bits per second. Analog and Digital Communications [Figure 7. Most of the lines in the telephone systems of the world at present are analog.

Signals are transmitted as continuous waves. This is a satisfactory way to transmit voice, but digital data sent by computers sequences of pulses representing 0s and 1s must be converted into an analog signal for transmission over an analog line. The analog data must then be converted back into digital before entering the memory of the receiving computer.

The conversion of data from digital form into analog for transmission and then back into digital at the receiving end is done by a pair of interface devices called modems mo dulator- dem odulator. Modem-based telecommunications have created a significant bottleneck in an environment where computer and peripheral speeds have increased dramatically. Digital lines are capable of much faster communication and digital circuitry is now cheaper than analog.

All the new equipment now installed in telephone networks is indeed digital. Trend: There is a shift toward digital telecommunications is taking place throughout the world. A digital system for telecommunications, called TI carrier , is in wide use in parts of the telephone network. With the geographical distribution of information systems, increased volumes of transmission, and the move to multimedia, the costs of telecommunications are a significant business concern. Two principal methods of reducing these costs are:.

Multiplexing - the sharing of a high-capacity link by a number of transmissions. Signal Compression - using the link more efficiently by removing redundancies from the signal. Characteristics of multiplexing:. There are economies of scale in telecommunications systems: the higher the system capacity, the lower the unit cost of transmissions.

Many individual transmissions can share a physical channel through a variety of techniques collectively called multiplexing. Multiplexing combines several lower-capacity transmissions into a single transmission, which is split at the receiving end.

Signal Compression. Characteristics of signal compression:. Signal compression is the reduction of the need for channel capacity by removing redundancies from the signal. To reduce the transmission needs, we can remove the redundancies at the sender site, transmit the compressed signal, and then restore the signal at the receiving end. Compression has an impressive effect on multimedia transmission needs.

Computer networks differ in scope from relatively slow wide area networks, employed to transmit messages across vast geographic distances, to very fast local area networks that may connect computers located in the same building. System designers may select one of several arrangements for interconnecting network nodes, depending on an organization's requirement.

There are several ways to establish a connection between the sender and the receiver of a message. Computers, switches, and terminals interconnected by network links are collectively called nodes. The purpose of network control is to provide a connection between nodes that need to communicate. The arrangement of nodes and links in a network is called a topology.

A variety of arrangements are possible, each with its own advantages and drawbacks. Network topology has to fit the structure of the organizational unit that will use the network, and this topology should also be adapted to the unit's communication traffic patterns and to the way the databases will be stored in order to facilitate access to them.

The following topologies are the most widely used:. Hierarchical Network. Hierarchical Network: [Figure 7. A corporate host computer often a mainframe , divisional minicomputers or powerful workstations, and workgroup support via micros.

Communication protocol

Data means information in digital format and communication means to exchange information between two or many users in anyways like speaking, texting, or any other modes of the medium. So, data communication is simply the exchange of data between two or many users through the transmission media like twisted pair cable, coaxial cable, optical fibers, radio wave, satellite microwave, etc. The user or device that sends the data is the source and the user that receives the data is a receiver. For data interchange to take place, the communicating devices must be a part of a system comprising of a combination of hardware and software. Its efficiency depends on four fundamental characteristics. Data channel means the flow of data or to carry the data from one device to another. In other words, we can say the data channel is a computer path or medium used to transfer the data from sender to receiver.

A network protocol is an established set of rules that determine how data is transmitted between different devices in the same network. Essentially, it allows connected devices to communicate with each other, regardless of any differences in their internal processes, structure or design. Network protocols are the reason you can easily communicate with people all over the world, and thus play a critical role in modern digital communications. Neither local area networks LAN nor wide area networks WAN could function the way they do today without the use of network protocols. Network protocols take large-scale processes and break them down into small, specific tasks or functions. This occurs at every level of the network, and each function must cooperate at each level to complete the larger task at hand.

The Open Systems Interconnection model OSI model is a conceptual model that characterises and standardises the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard communication protocols. The model partitions the flow of data in a communication system into seven abstraction layers , from the physical implementation of transmitting bits across a communications medium to the highest-level representation of data of a distributed application. Each intermediate layer serves a class of functionality to the layer above it and is served by the layer below it. Classes of functionality are realized in software by standardized communication protocols.


The major components of a network are end stations, applications and a network that will support traffic between the end stations. Computer networks all share.


Network Standards (Data Communications and Networking)

A communication protocol is a system of rules that allow two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax , semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware , software , or a combination of both. Communicating systems use well-defined formats for exchanging various messages.

Мидж покачала головой. - В Космополитене пишут, что две трети просьб потереть спинку кончаются сексом. Бринкерхофф возмутился. - У нас ничего такого не случалось. - Вот .

How Network Protocols Work

Как только получит денежки, так и улетит. Беккер почувствовал тошноту. Это какая-то глупая шутка. Он не находил слов. - Ты знаешь ее фамилию.

В Севилье есть больницы получше. - Этот полицейский… - Клушар рассердился.  - Он уронил меня с мотоцикла, бросил на улице, залитого кровью, как зарезанную свинью. Я еле добрел. - Он не предложил вам больницы поприличнее. - На этой его чертовой тарантайке. Нет уж, увольте.

ГЛАВА 87 Веспа выехала в тихий переулок Каретерра-де-Хуелва. Еще только начинало светать, но движение уже было довольно оживленным: молодые жители Севильи возвращались после ночных пляжных развлечений. Резко просигналив, пронесся мимо мини-автобус, до отказа забитый подростками.

Сьюзан словно отключилась от Хейла и всего окружающего ее хаоса. Энсей Танкадо - это Северная Дакота… Сьюзан попыталась расставить все фрагменты имеющейся у нее информации по своим местам. Если Танкадо - Северная Дакота, выходит, он посылал электронную почту самому себе… а это значит, что никакой Северной Дакоты не существует.

Его копчик больно вдавливался в низ ее живота через тонкую ткань юбки. Кровь из ноздрей капала прямо на нее, и она вся была перепачкана. Она чувствовала, как к ее горлу подступает тошнота. Его руки двигались по ее груди. Сьюзан ничего не чувствовала.

Он понимал, что мы могли решиться на это только в одном случае - если нашли Северную Дакоту. По спине Сьюзан пробежал холодок.

Он попробовал встать, но настолько выбился из сил, что не смог ступить ни шагу и долго сидел, изможденный вконец, на каменных ступеньках, рассеянно разглядывая распростертое у его ног тело. Глаза Халохота закатились, глядя в пустоту. Странно, но его очки ничуть не пострадали.

5 Comments

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  3. Kowshotalboa 09.01.2021 at 18:28

    To reduce the design complexity, most of the data communication networks are organized as a series of layers or levels, each one build upon one below it (​Divide.

  4. Leon H. 11.01.2021 at 03:03

    Chapter 7.

  5. Shamara M. 13.01.2021 at 21:45

    Data Communication is defined as exchange of data between two devices via some form of transmission media such as a cable, wire or it can be air or vacuum also.