DATA COMMUNICATION & NETWORKING

DATA COMMUNICATION & NETWORKING

Q:1 what is Networking ?
Ans: In the world of computers* networking is the practice of linking two or more computing devices together for the purpose of sharing data. Networks are built with a mix of computer hardware and computer software.

Q:2 What is Protocol? How many types of Protocols are there?
Ans: When computers communicate with each other* there needs to be a common set of rules and instructions that each computer follows. A specific set of communication rules is called a protocol.
Because of the many ways computers can communicate with each other* there are many different protocols -- too many for the average person to remember. Some examples of these different protocols include PPP* TCP/IP* SLIP* HTTP* and FTP.
Data Flow

    * A simplex channel is a one-way channel.
    * A half-duplex channel is one that can carry information in both directions* but not at the same time.
    * A full-duplex channel is a channel which can carry information in both directions at once.

Q:3 what is simplex communication?
Ans:
Simplex communication - Definition


A simplex communication system is one where all signals flow in one direction.
These systems are often employed in broadcast networks* where the receivers do not need to send any data back to the transmitter/broadcaster.
Examples

    * [Only Registered and Activated Users Can See Links. Click Here To Register...] broadcast
    * Commercial [Only Registered and Activated Users Can See Links. Click Here To Register...] broadcast (not [Only Registered and Activated Users Can See Links. Click Here To Register...]* etc.)

Q:4 what is half-duplex communication?
Ans: Half-duplex data transmission means that data can be transmitted in both directions on a signal carrier* but not at the same time. For example* on a local area network using a technology that has half-duplex transmission* one workstation can send data on the line and then immediately receive data on the line from the same direction in which data was just transmitted. e.g

Q:5 what is Full Duplex communication?
Full duplex on the other hand is the communication netword that allows communication at both sides at the same time. E.g telephone.
Simple Definition
[Simplex devices offer only one way communication. In this type of communication one side only receives the data and other side can only send it. E.g STU
Half Duplex are the devices that allow communication on both sides where bothe sides can send and receive data signals but on separate time. E.g Voice chat on [Only Registered and Activated Users Can See Links. Click Here To Register...] or MSN messenger.
Full duplex on the other hand is the communication netword that allows communication at both sides at the same time. E.g telephone.]
Fundamental Parameters of Data

The effectiveness of data communication system depends upon following four fundamental characteristics:
1. Delivering Data Packets
2. Accuracy
3. Timelessness
4. Jitter
Variation in packet arrival time

Data Communication System Components

1. Message
2. Sender
3. Receiver
4. Medium
5. Protocol

Data Communication System



Data Representation

? It has different forms
Text* number* image* audio* video


Mode of Transmission

? Mode of transmission or data flow between two devices can be
1. Simplex
2. Half Duplex
3. Full Duplex






Networks

? Define Network
? Set of devices connected through communication link.
? Node
? It can be computer* printer or any other device capable of sending/ receiving data.
? Distributed Processing
1. Security
2. Distributed Databases
3. Faster problem solving
4. Security through redundancy
5. Collaborative processing

Network Criteria


Performance

Performance can be measured in many ways including transit and response time.
? Transit time
? Response time
? The performance of network depends upon
? Number of Users
? Type of Transmission Medium
? Hardware( buffer* speed etc)
? Software ( raw data conversion and reassembly)

Reliability ( robustness)
? Frequency of Failure
? Recovery time of a network after a failure
? Catastrophe

Security

? Unauthorized Access
? Viruses
? Hacking etc..
Protocols & Standards

? Define Protocol? ( what* how and when)
? Entity ( data base management* browse* FTP)
? Any thing capable of sending and receiving the information
? Key elements of Protocol
1. Syntax ( format of data)
2. Semantics ( meaning of each section of bits)
3. Timing ( when to send and how fast to send)


Standards


? Standards are essential in creating and maintaining an open and competitive market for the manufacturer
? Standards provide guidelines
? Data communication standards fall into two catagories


? De Jure ( By Law)
? Those standards that has been legislated by an officially recognized body * forums and government agencies.
? De Facto ( By Fact)
? Those standards established by manufacturer* who seek functionality of new product.

Standard Organizations
? Developed by Cooperation among standards creation committees* forums and government regulatory agencies
? Standards Creation Committees
1. ISO
2. ITU
3. ANSI
4. IEEE
5. EIA
6. Telcordia

Forums

? Frame relay Forum
? ATM forum
? Internet Society( ISOC) and Internet Engg Task force
( IETF)



Regulatory Agency
? Purpose is to protect the public interest
? PTA
? FCC
? BTC
Regulatory Agencies
Following are the responsibilities of regulatory agencies
? To review rate and service charge applications made by telegraph and telephone providers.
? To review the technical specifications of communications hardware.
? To establish reasonable common carrier rates of return.
? To divide and allocate radio frequencies.
? To assign carrier frequencies for radio and TV broadcast.




Mesh Topology
Mesh
? Dedicated link
? Robust
? Security
? Fault identification is easier
Disadvantage
? Amount of cabling and I/O ports
? Installation is difficult and reconfiguration too
? Bulk of wiring may be more than spacing

Star Topology


Star
? Less expensive
? Simple due to one I/O port
? Installation and conf is easier
? Robustness
? Self fault identification
Disadvantages
? Hub is down then?..

Tree Topology


Tree
? Same as Star
Bus Topology



Bus
? Ease of installation
? Less cabling
? In same room 4 cables for star where as 1 cable in case of bus
Disadvantage
? Difficult in reconfig and fault isolation
? Low scalability
? When bus is down all network will be down.
Ring
? Fault isolation is simple
? Alarming
Disadvantages
? Ring breaks then?
? Station is dead