Data Communications and Networking

Introduction to Data Communications and Networking

• Data communications and networking are changing business practices and lifestyles
• Decision-makers require immediate access to accurate data more than ever
• Businesses are relying on computer networks and internetworks
• It's essential to understand how the networks operate, technologies available, and designs to fulfill needs
• Personal computers have brought a revolution in business, industry, science, and education
• Advances are expanding communication links and capacity
• Telephony services like conference calling, voice mail, and caller ID are evolving

Goal of Data Communications

• Enable data exchange (text, audio, video) from anywhere in the world
• Allow quick access to downloading and uploading information effectively

Chapter Focus: Four Key Issues

• Data communication
• Networks
• The internet
• Protocols and standards

Data Communications Defined

• Data communications is the exchange of data between two devices via a transmission medium.
• Sharing information can be local or remote.
• Telecommunication is communication at a distance, with "tele" derived from the Greek word for "far".
• Data is information in an agreed-upon format by the creators/users

Essential System Characteristics

• Communicating devices include both hardware and software
• Delivery: A system must deliver data to the correct destination using users intended devices
• Accuracy: A system must deliver accurate data, that hasn't been altered in transmission or unusable
• Timeliness: A system must deliver data in a timely manner for it to be useful
• Real-time transmission involves delivering audio and video data in the order it was produced and without major delays

Data Communications System Components:

• Message: The information to be communicated (text, numbers, etc.).
• Sender: The device that sends the data message (computer, etc.).
• Receiver: The device that receives the message (computer, etc.).
• Medium: The physical path for transmission (cable, fiber optics, radio waves).
• Protocol: The rules governing the data communications (agreement between devices).

ISO/OSI

• The International Standards Organization (ISO) Open Systems Interconnect (OSI) is a standard set of rules describing the transfer of data between each layer
• Each layer has a specific function like electrical and cable specifications
• The OSI Model defines the interfaces between each layer, that allows different network operating systems protocols to work together
• The ISO OSI model has allowed the modern multi-protocol networks that exist today
• There are 7 Layers of the OSI Model:
• Application Layer (Top Layer)
• Presentation Layer
• Session Layer
• Transport Layer
• Network Layer
• Data Link Layer
• Physical Layer (Bottom Layer)

LANs

• LAN (local area networks) are networks connect computers and resources together in a building or buildings close together
• The components used by LANS are divided into cabling standards, hardware and protocols.

MANs

• MAN (Metropolitan Area Networks) are networks that connect LANs together within a city
• The main criteria for a MAN is that the connection between LANs is through a local exchange carrier (phone company)
• The protocols that are used for MANs are quite different from LANs except for ATM

WANs

• WANs (Wide Area Networks) connect LANs together between cities
• The main difference between a MAN and a WAN is that the WAN uses Long Distance Carriers

Basic Components

• Source: it is the transmitter of data. Examples are terminal, computer, mainframe
• Medium: The communications stream through which the data is being transmitted such as Cabling, Microwave, Fibre Optics, Radio Frequencies, Infrared Wireless Receiver: The receiver of the transmitted data includes printer, terminal, mainframe, computer

DCE and DTE

• DCE (Data Communication Equipment): The interface between the Source & the Medium, and the Medium & the Receiver is a physical piece of equipment
• DTE (Data Terminal Equipment): Data Terminal Equipment is the Telecommunication name given to the Source and Receiver's equipment

Data Representation: Text

• Text is represented as a bit pattern, a sequence of bits (0s or 1s)
• The number of bits depends on the number of symbols in the language
• Each bit pattern designed to represent symbols is called a code

ASCII

• The American National Standards Institute developed a code called the American Standard Code for Information Interchange
• This code uses 7 bits for each symbol, meaning 128 symbols can be defined in this code

Extended ASCII

• To make each pattern I byte (8 bits), the ASCII bit patterns are augmented with an extra O at the left

Unicode

• This uses 16 bits and can represent up to 65.536 (216) symbols that are allocated to symbols from different languages in the world and for graphical and special symbols.

ISO

• The International Organization for Standardization, known as ISO, has designed a code using a 32-bit pattern that can represent up to 4.294,967,296 (232) symbols,

Numbers

• Numbers are also represented by using bit patterns by directly converting to a binary number

Images

• Today, images are represented by patterns are divided into a matrix of pixels which depends on what is called the resolution

Audio

• Audio is continuous meaning it is a representation of sound that is by nature different from text, numbers, or images

Video

• Video is a continuous entity or it can be a combination of images, each discrete entity arranged to convey the idea of motion

Data Flow Direction

• Communication between two devices can be simplex, half-duplex, or full-duplex.

Simplex

• In simplex mode, the communication is unidirectional, as on a one-way street