DATA COMMUNICATION & NETWORKS

Data Communication

Exchange of data between two or more

devices using some transmission

medium.

Another explanation could be:

Electronic transmission of information

that has been encoded digitally (as for

storage and processing by computers)

Components of Data Communication System

Message (text, image, numbers, audio, video)

Sender(computer, workstation, telephone, camera etc.)

Receiver

Transmission Medium(twisted-pair, optical fiber, coaxial cable, radio waves)

Protocol(set of rules that govern data communication)

Mode of Data Communications

Simplex (unidirectional)

Half-Duplex (bidirectional)

Full-Duplex(bidirectional)

Applications of Networks

Resource Sharing

Hardware (Computing Resources, Disks, Printers, etc.)

Software (Application Software)

Information Sharing

Easy accessibility from anywhere (Files, Databases, etc.)

Search Capability (WWW)

Communication

Email

Message Broadcasting

Network Criteria

Performance:

Transmit Time, Response Time, Throughput

Reliability:

Frequency of failure, Time to recover

Security:

Unauthorized Access, Protecting Data

Physical Topology

It refers to the way how the network is laid out physically.

Geometric representation of the relationship of all the links and linking devices

Types of Physical Topologies

Mesh Topology

Star Topology

Bus Topology

Ring Topology

Hybrid Topology

Mesh Topology

Star Topology

Bus Topology

Ring Topology

Hybrid Topology

Categories of Networks

Local Area Network (LAN)

Wide Area Network (WAN)

Metropolitan Area Network (MAN)

Local Area Network

Privately owned computer network that connects computers and other information processing device.

LAN size – Few Kilometers

LAN Examples

Ethernet (CSMA/CD)

LocalTalk (CSMA/CA)

Wireless LAN

Token Ring

LAN

Wide Area Network

Network that covers a broad area

Example- Any telecommunications network that links across metropolitan, regional, or national boundaries.

WAN

Metropolitan Area Network(MAN)

Designed to extend over the entire city.

It may be a single network as a cable TV network OR

It may be means of connecting a number of LANs into a larger network

The main reason for distinguishing MANs as a special category is that a standard has been adopted for them. It is DQDB(Distributed Queue Dual Bus) or IEEE 802.6.

Protocols and Standards

Protocol: Syntax

The structure or format of data, i.e. the order in which they are presented.

Semantics

Semantics refers to the meaning of each section of bits.

Timing

When and how fast data to be sent.

Standards:

De facto Standards -

Not approved by an organized body.

De jure Standards -

Approved by an organized body.