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Introduction to Data Communications and

Networking

Ranil Montaril, ECE

Data Communications

Communications- a two way process of exchanging intelligent information from one point to another.

Components:1. Source2. Transmitter3. Transmission System/ Medium4. Receiver5. Destination

Simplified Communication Model

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Components of Communications System

n Source– generates data to be transmitted

n Transmitter– Converts data into transmittable signals

n Transmission System– Carries data

n Receiver– Converts received signal into data

n Destination– Takes incoming data

Data

Data- Information or intelligence that has been processed and organized into its digital form.

Form of Data:1. Voice2. Video3. Picture4. Texts 5. Microprocessor Op codes6. ASCII

Data Communications

n Data Communications

– The process of communicating information in a binary form between two points in such as way that data must be translated into a special code for transmission.

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Data Communications Model

Data Communications Circuit

Data Communications Circuit

n Data Terminal Equipment (DTE)– Includes all data processing equipments (i.e.

Computers, I/O units, displays, remote access or read only devices)

n Data Communications (DCE)– A device capable of establishing, maintaining,

terminating a connection. The DCE may have signal conversation and coding.

n Communication Link (Medium)– May consists of Physical circuit (wire, cables, optical

wires) and serve as a highway of data.

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DTE-DCE/ DCE-DCE Interfacingn DTE-DCE or DCE-DTE Interfacing

– Connected in Parallel Interfacing.

n DCE-DCE Interfacing– Connected in Serial Interfacing.

Interfacing

n Parallel Interface– Each bit has its own transmission line, and bits are transmitted

and received simultaneously during the time.

Ex: Data is in the format of

A3 A2 A1 A0 = 1001

MSB

A3

A2

A1

A0

LSB

MSB

A3

A2

A1

A0

LSB

1

0

0

1

Interfacing

n Serial Interface– A single transmission line, thus only one bit at a time

can be transmitted and received as well.

A3 A2 A1 A0

1 0 0 1

Ex: Data is in the format of

A3 A2 A1 A0 = 1001

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Historical Backgroundn Telegraphy

– Communications at a distance by code signals the consists of correct pulses present over wires or radio.

§ In 1837, Samuel Morse exhibited a working telegraphy system (first electronic data communication system).

§ In 1844, the first telegraph was established between Baltimore &Washington DC.

§ In 1849, the first slow telegraph printer was invented but it wa s not until 1860, that the high speed printer (15 bps) printer was ava ilable.

§ In 1850, Western Union Telegraphy company was formed in Rocheste r, NY for the purpose of carrying coded messages from one person toanother.

§ In 1887, Emile Baudot invented a telegraph multiplexer, w/c allowed signals from up to six different telegraph machines to be transmitted simultaneously over a single wire.

Historical Background

n Telephony– Transmission of speech & sounds to distant point for

communication purposes.

§ In 1876, Alexander Graham Bell invented the first telephone capable for practical use.

§ In 1879, the first manual telephone switch board was installed (PBX-Private Branch Exchange).

§ In 1880, the first pay phone was available for use.

Historical Background

n Telecommunications Company– Any transmission, emission, or reception of signals,

writing images, sounds, or intelligence or any nature by wire , radio, visual or other electromagnetic system.

§ In 1885, the AT&T (American Telephone & Telegraph) company was registered.

§ In 1968, the AT&T operating tariffs allowed only equipment furnished by AT&T to be connected to AT&T lines.

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Historical Background

n Telephone Regulatory Body

§ In 1910, the ICC (Interstate Commerce Communication) had the authority to regulate interstate telephone business.

§ In 1934, President Roosevelt approved the communication set ( which transferred ICC regulatory power to FCC).

Historical Background

n Special Purpose Computer

§ In 1940, Bell Laboratory developed the first special purpose computer using electromechanical relays.

n Transistor Technology– The invention of transistor is the start of Electronic

Switching System in Telephone Central Office.

§ In 1947, transistor was invented at Bell Laboratories.

Historical Backgroundn Long Distance Direct Dial

– It is design of impulsing circuits so that it become possible to examine the prospect of providing dialing facilities over greater distance.

§ In 1951, the DDD customer dialing began.

n Satellite Connection– Communication with an active or passive satellite to extend the range

of radio, television, or other transmitter by returning signals to earth from an orbiting satellite.

§ In 1962, the first international satellite telephone call was sent over TELSTAR.

§ In 1965, there was wide spread introduction of commercial international service by satellite.

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Historical Background

n Touchstone (DTMF)– A telephone that has 12 pushbutton, each of which produces a

distinctive two frequency musical tone which initiates the proper automatic switching in the telephone exchange, just as the DC pulsing of a rotating dial tones.

§ In 1963, touchstone telephone began to be marketed.n Break of Monopoly

§ In 1968, the famous Carterfone Court decisions stated that non-Bell equipment shall be connected to the Bell System Network.

Historical Background

n Picturefone Service– A small television screen along side each telephone that allows

parties to see each other as they converse over the telephone.

§ In 1969, picturefone service allows user to see as well as or talk with one another.

n Cellular Telephones– A terrestrial mobile telephone system based on radio links for

transmission & reception to a fixed transceiver station or relayback to the telephone central office.

§ In 1983 – 1984, traditional radio telephone type calls were supplanted by the newer cellular telephone network.

Historical Background

n Ballistic Transistor§ In 1985, Bell Laboratories has invented another new

transistor that operate 1000 times faster than the original transistor in 1947.

n ISDN– Integrated Service Digital Network

§ In 1986, the ISDN began serving the public.(Thisnetwork allows, the simultaneous transmission of voice, data & video images.)

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Historical Background

n Commercialize Communication Service– Deregulation of different communication

company that resulted in competition.

§ In 1987, there was considerable competition in both voice to data communication markets as a number of independent companies began to sell communication services in manner similar to that automobile marketing.

Historical Background

Applications of Data Communications

n Source Data Entry and Connection– Sales action data, Inventory Control, payroll data gathering.– Point of Sale System, Airline Reservation.

n Remote Job Entry (R/E)– Local Access to distant Human Resourcing.

n Information Retrieval– Checking Bank Status, Insurance Policy Status.

n Conversational Timen Message Switching

– Emailn Time data acquisition and process control

– automationn Interprocessors Data Exchange

– File sharing of all types of application.

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Data Communications Standards

n Standards– Guidelines that have been generally accepted by the

data communication industry.

Types of Standards:– Proprietary (closed) system§ Generally manufactured and controlled by one company.

– Non Proprietary (open) system§ Any company that can produce compatible equipment or

software ; however, often a royalty must be paid to the original company.

Standards Organizations for Data Communications

n International Standards Organization (ISO)– An international organization for

standardization that creates sets of rules and standards for graphics, document exchange, & related technologies.

– It is also responsible for endorsing and coordinating the work of the other standards organizations.

Standards Organizations for Data Communications

n Consultative Committee for International Telephony & Telegraphy (CCITT)– Currently known as ITU (International

Telecommunication Union).– Consists of government authorities and rep from

many countries.– Develops the recommended set of rules and

standards in telephone and telegraph communications.

– Three Specifications were developed, the V series –for modem interfacing, the X series for Data Communications, and the I & Q series for ISDN standards.

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Standards Organizations for Data Communications

n American National Standard Institute (ANSI)

– The official standards agency for the US voting representative for ISO

Standards Organizations for Data Communications

n Institute of Electrical and Electronics Engineers (IEEE)

– A US professional organization of electronics, computer, and communications engineers.

Standards Organizations for Data Communications

n Electronics Industries Association (EIA)

– A US organization that establishes & recommends industrial standards.

– Responsible for developing the RS (recommended standard) series of standards in Data Communications.

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Standards Organizations for Data Communications

n Standards Council of Canada (SCC)

– Official Standard agency of Canada with similar responsibilities to those of ANSI.

Data Communications Network

n Data Communications Network– Any system of computers, computer terminals

or computer peripheral equipment used to transmit or receive information between two or more locations

Data Communications Network Model

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Objective of Data Communication Networks

n Reduce time and Effort required to perform various business tasks.

n Capture Business data at its source.n Centralize control over Business data.n Effect rapid dissemination of information.n Reduce of doing business.n Expansion of business capacity.n Support & improve management control of

Organizations.

Data Communications Protocol

n Data Communications Protocol– Sets of rules governing the orderly exchange

of data within the network or a portion of network, whereas network architecture is a set of layers and protocols that govern the operation of the network.

Classifications of Protocols:§ Connection Oriented§ Connectionless Oriented

Classifications of Protocols

n Connection Oriented– A logical connection is established between endpoints (i.e.

virtual circuit) prior to the transmission of data.

Characteristics:§ A connection process called a handshake that occurs bet. two

stations before any data are actually transferred.§ Mostly, requires some means of acknowledging the data as they

are being transmitted.§ Often provide some means of error control (i.e. error detection

and correction).§ When a connection is no longer needed a specific handshake

drops the connection.

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Connection Oriented Protocols

Clear ResponseConnection Clear Request

Data AcknowledgementData Transmitted

Setup ResponseSet up request

Classifications of Protocols

n Connectionless Protocols– Protocols where data are exchanged in an unplanned fashion

without prior coordination between endpoints (i.e. datagrams)

Characteristics:§ It sends data with a source and destination address without

handshake to ensure that destination is ready to receive the data.

§ Usually do not support error control or acknowledgment procedures, making them a relatively unreliable method of data transmission.

§ It is more efficient , as data being transmitted usually do not justify the extra overhead required by connection-oriented protocol.

Connectionless Oriented Protocols

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Elements of Protocol

n Syntax– Refers to the structure or format of a data

within the message.

n Semantics– Refers to the meaning of each section of data.

n Timing– Refers to when and how fast the data was

sent.

Q & A???