Data Communication and Network Components: Modes, Devices, and Media - Prof. Assefa, Lecture notes of Introduction to Computing

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Chapter 2

Data Communication

and

Network Components

Outline

❖Communication

❖Data Communication

❖Modes of Data Communication

❖Components of the network Devices

❖Network Media

What is Data Communication?

 Communication is simply the act of transferring information from one place, person or group to another.  Data communication (also data transmission or digital communications) is the transfer of data (a digital bitstream or a digitized analog signal) over a point-to-point or point-to-multipoint communication channel.

Data Communication

 Data communication involves transporting data from

one point to another.

 In data communication, five basic elements can be

identified.

 The source (the sender)

 The medium (the channel)

 The destination (receiver)

The Information(message)

The communication Protocol

Data Communication There are five components in data communication system.  Message : the information to be communicated  Sender : the device that sends the message  Receiver : the device that receives the message  Medium : the transmission medium is the physical path that communicates the message from sender to receiver.  Protocol : refers to a set of rules that coordinates the exchange of information. Both the sender and the receiver should follow the same protocol to communicate data.

Data Communication Model

Messages

 The messages or units of information that travel from one device to another  In the first step of its journey from the computer to its destination, message gets converted into a format that can be transmitted on the network.  All types of messages must be converted to bits, binary coded digital signals, before being sent to their destinations.  This is true no matter what the original message format was: text, video, voice, or computer data. Once our instant message is converted to bits, it is ready to be sent onto the network for delivery.

Network Devices Sender/Receiver  Devices on the network that exchange messages with each other.  Senders and Receivers are network devices.  Switch  Firewall-provides security to networks  Router- helps direct messages as they travel across a network  Wireless Router  Serial Link - one form of WAN interconnection, represented by the lightning bolt-shaped line

Network Devices

Rules/Protocols

 Rules or agreements to govern how the messages are sent, directed, received and interpreted.  Rules are the standards and protocols that specify how the messages are sent, how they are directed through the network, and how they are interpreted at the destination devices

Modes of Data Communication

When data are transmitted from one point to another, three modes of transmission can be identified: Simplex Half Duplex Full Duplex

Simplex Data Communication Mode  In simplex mode, data is transmitted in only one direction.  A terminal can only send data and cannot receive it or it can only receive data but cannot send it.  Simplex mode is usually used for a remote device that is meant only to receive data.  It is not possible to confirm successful transmission of data in simplex mode.

Simplex Data Communication Mode  This mode is not widely used.  Examples  Speaker, radio and television broadcasting are examples of simplex transmission, on which the signal is send from the transmission to your TV antenna.  There is no return signal. SENDER UNIDIRECTIONAL RECEIVER

Half-Duplex Data Communication Mode  In half duplex mode, data can be transmitted in both directions but only in one direction at a time.  During any transmission, one is the transmitter and the other is receiver.  So each time for sending or receiving data, direction of data communication is reversed, this slows down data transmission rate.

Half-Duplex Data Communication Mode  In half duplex modes, transmission of data can be confirmed SENDER/ RECEIVER RECEIVER/ SENDER BIDIRECTIONAL BIDIRECTIONAL

Full Duplex Data Communication Mode  In full mode, data can be transmitted in both directions simultaneously.  It is a faster mode for transmitting data because no time wastes in switching directions.  Example of full duplex is a computer network in which both the users can send and receive data at the same time.  Telephone conversation, Internet

Full Duplex Mode

SENDER/ RECEIVER BIDIRECTIONAL RECEIVER/ SENDER

Simplex, Half Duplex & Full Duplex Simplex Half Duplex Full Duplex Cost (^) Cheapest communication Expensive Most Expensive Data transmission One way Two way one at a time Simultaneous transmission Bandwidth (^) Low Medium High

Communication Signals  There are two types of Communication Signals. These are  Digital Signal  Analog Signal Digital signal:  A signal which is discrete with respect to time is called digital signal.  Such signal can be modeled using binary number system as shown in the figure below.

Communication Signals

Analog signal  is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity.

Components Network Devices

 End network Devices  Intermediary network Devices

End Devices and Their Roles on the Network End Devices  The network devices that people are most familiar with are called end devices.  These devices form the interface between the human network and the underlying communication network.  A source or destination device in an end networked system  end devices are referred to as hosts.

End Devices

Some examples of end devices are:  Computers  Desktops  Laptops  Tablet  file servers, web servers)  Network printers  VoIP phones  Mobile handheld devices ( PDAs)

End Devices

 A host device (end devices) is either the source or destination of a message transmitted over the network.  In order to distinguish one host from another, each host on a network is identified by an address.  When a host initiates communication, it uses the address of the destination host to specify where the message should be sent.

Intermediary Devices

 In addition to the end devices that people are familiar with, networks rely on intermediary devices to provide connectivity and to work behind the scenes to ensure that data flows across the network.  These devices connect the individual hosts (end devises) to the network and can connect multiple individual networks to form an internetwork.  Internetworking is the process or technique of connecting different networks by using intermediary devices such as routers or gateway devices