Network Fundamentals



Data Communication

The most important consideration of a data communication:

1.    Performance

2.    Transmission rate

3.    Reliability

4.    Security

Transmission Modes:

There are three mode of transmission for data communication

  1. Simplex: In simplex (SX) mode, data transmission is unidirectional information can be sent in only one direction. It is also called one-way-only lines. E.g. Commercial radio broad casting.
  2. Half-duplex: In the half-duplex (FIDX) mode, data transmission is possible in both direction but not at the same time. It is also called either way lines. E.g. Citizens band (CB) radio is an example of half-duplex.
  3. Full duplex: In full duplex (FDX) mode, transmission is possible in both directions simultaneously but they must be between the same two stations. It is also called both-way lines. E.g. Mobile phone call.

Components of Data communication:

There are five components of data communications:

1.    Message: It can be text, number pictures, sound or video or any combinations.

2.    Sender: These send the data message it can be a computer workstation and so on.

3.    Receiver: The device that receives the message it can be computer workstation, telephone handset.

4.    Medium: The physical path by which a message travel from sender to receiver. E.g. radio waves twisted pair coaxial cable. Etc

5.    Protocol: A set of rules that govern data communication.

Network Classification:

Networks one generally classified by size, which includes geographic area, distance between stations, number

of computers, transmission speed (bps), transmission media of the network physical or architecture.

1.    LAN: Local Area Network

Local Area Network (LAN) are typically privately owned data communication network in which 10  to 100 Computer users share data resources with one or more file servers. LAN uses a network operating system to Provide two way communications at bit rate in the range of 10 Mbps to 100 Mbps. E.g. same room, building, campus. The LANs link equipment within a few km. The most common LAN topologies arc bus, ring and star.

2.    MAN: Metropolitan Area Network:

A Metropolitan Area Network (MAN) is a high speed network similar to a LAN except MAN are designed to encompass large area usually that of an entire city MANs operate at speed at 1 .5 Mbps to 10 Mbps and range five miles to a few hundred miles in length. A MAN generally uses only one or two transmission cable and requires no switches A MAN could be a single network such as a cable television distribution network or it could be inter connecting two or more LAN into o single larger network enabling data resources to be Shared LAN to LAN on will and from station to station or computer to computer.e.g

(1) Switched Multimedia bit data services (SMDS)

(2) Fiber distributed data inter fall (FDDF)

(3) Asynchronous Transfer mode (ATM)

3.    WAN: Wide Area Network:

A Wide- Area Network provides long distance transmission of data voice, image and view information over large geographic areas that may comprise country continent or the whole world WAN typically operate at bit rates from 1.5 Mbps to 2.4 Gbps and cover distance of 400 to 1000 miles. WAN may utilize both public and private communication system to provide service an area that is virtually unlimited. E.g. ISDN, X. 25, ATM, Frame Relay.