Data Communication and Networks

Data Communication and Networks

Chapter 6

Principles of data communication

• Exchange of digital information between 2 digital devices– Message, Sender, Medium, Receiver and

Protocol

Analogue Signal• An analog or analogue signal is any

continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal.

Digital Signal• digital signal is a physical signal that is a

representation of a sequence of discrete values (a quantified discrete-time signal), for example of an arbitrary bit stream, or of a digitized (sampled and analog-to-digital converted) analog signal.

transmission media• A transmission medium is a material

substance (solid, liquid, gas, or plasma) that can propagate energy waves. For example, the transmission medium for sounds is usually air, but solids and liquids may also act as transmission media for sound.

Transmission mode• Transmission mode means transferring of data

between two devices. It is also called communication mode. These modes direct the direction of flow of information. There are three types of transmission mode. They are :– Simplex Mode– Half duplex Mode– Full duplex Mode

Synchronous Transmission• sender and receiver use the same clock

signal• supports high data transfer rate• needs clock signal between the sender

and the receiver• requires master/slave configuration• is carried out under the control of the

timing source

asynchronous transmission• sender provides a synchronization signal

to the receiver before starting the transfer of each message

• does not need clock signal between the sender and the receiver

• slower data transfer rate• Sending end commences the

Transmission of bits at any instant of time

communication equipment• facility consisting of the physical plants

and equipment for disseminating information

communication protocol• A communications protocol defines the

rules for sending blocks of data (each known as a Protocol Data Unit (PDU)) from one node in a network to another node. Protocols are normally defined in a layered manner and provide all or part of the services specified by a layer of the OSI reference model.

OSI Layer

Local Area Networks• A local area network (LAN) is a computer

network that interconnects computers within a limited area such as a home, school, computer laboratory, or office building, using network media.

Wide Area Networks• A wide area network (WAN)

is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, national or international boundaries) using leased telecommunication lines.

topologies• is the arrangement of the various elements

(links, nodes, etc.) of a computer network. Essentially, it is the topological structure of a network and may be depicted physically or logically.