Notes Data Communication And networking

HTTP Full Form is Hypertext Transfer Protocol. It is the dada communication foundation for the World Wide Web (WWW)

The File Transfer Protocol (FTP) is a standard network protocol used to transfer computer files between a client and server on a computer network. 

 SMTP: Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers

IMAP (Internet Message Access Protocol) is a standard email protocol that stores email messages on a mail server, but allows the end user to view and manipulate the messages as though they were stored locally on the end user's computing device(s).

POP:- a protocol used to retrieve e-mail from a mail server. Most e-mail applications (sometimes called an e-mail client) use the POP protocol, although some can use the newer IMAP (Internet Message Access Protocol).

SLIP: SLIP is an Internet protocol that allows users to gain Internet access using a computer modem

PPP: Point-to-Point Protocol (PPP) is a data link (layer 2)protocol used to establish a direct connection between two nodes

TCP: TCP works with the Internet Protocol (IP), which defines how computers send packets of data to each other.

GSM: GSM (Global System for Mobile communications) is an open, digital cellular technology used for transmitting mobile voice and data services.

CDMA: CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies.

Difference between GSM and CDMA

  1. GSM is Narrow Band while CDMA is wide Band Technology

    2. GSM is time division(TDMA) while CDMA use Code DIVISION (CDMA)

TRANSMISSION MEDIUM:

Transmission medium is the means through which we send our data from one place to another. The first layer (physical layer) of Communication Networks OSI Seven layer model is dedicated to the transmission media,

Factors to be considered while choosing Transmission Medium

1.    Transmission Rate

2.    Cost and Ease of Installation

3.    Resistance to Environmental Conditions

4.    Distances

	Speed	Bandwidth	Attenuation
Twisted pair		100-500 Mbps	high
Coaxial cable		10 Mbps	Moderate
Optical fibre		100 Mbps- 2Gbps	none

Repeater : In telecommunications, a repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.

Switch: A network switch is a computer networking device that connects devices together on a computer network,

Hub: A hub is a common connection point for devices in a network.
Difference between Switch and Hub

1. Hub is a dumb device while switch is smarter device than hub
2. Hub Broadcast the message in network which leads to traffic load while switch sends the packets to only desired desitination

Bridge: In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol .

Gateway : it is a device to connect two dissimilar network

Modem :- it is a device which converts analog signal to digital and vice versa
Modem may be of two types      1. Internal Modem    2. external Modem

NIC: Nic is Ethernet card which contains connection for twisted pair cable or co axial cable.

Router : A router is a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet

Topology :  a topology is a usually schematic description of the arrangement of a network, including its nodes and connecting lines. 

1.    Bus topology/linear topology

2.    Tree topology

3.    Ring topology

4.    Star topology

5.    Mesh topology

6.    Fully connected network.

ARPANET :- ARPANET is advanced research project agency network. It was first network developed by us defence. Late it was connected to NSF(National science foundation) which became Internet later.

Circuit Switching : With this type of switching technique, once a connection is established, a dedicated path exists between both ends until the connection is terminated.

Message  Switching: With message switching there is no need to establish a dedicated path between two stations. When a station sends a message, the destination address is appended to the message.

•     The entire message is then transmitted through the network, from node to node.

•     Each node receives the entire message, stores it , and then transmits the message to the next node.

•      This type of network is called a store-and-forward network.

Packets  Switching : In packet switching methods, a message is broken into small parts, called packets. Each packet is tagged with appropriate source and destination addresses. They do not necessarily travel together; they do not travel sequentially. They don't even all travel via the same route.But eventually they arrive at the right point and at their destination are reassembled into the correct order,

Cookies:- cookies are information sent by server to client computer to keep the track of work performed in client computers.

Firewall :- it is system designed to prevent unauthorized access to or from a private network. It can be implemented in both hardware and software.

Hacker:- hackers are programmer who break into the system for learning and joy purpose

Cracker: - crackers are malicious programmers who break into secure system with bad intention

Telnet:-telnet is service/utility which helps in remote login. With the help of telnet we can login into remote computer and can do the work as we are doing work in local computers

Proprietary software:- it is software which is neither  free  nor open. It belongs to some person/organization. To sue this software we have to purchase license by paying amount from its proprietor
ODF: - it is an open document format, based on XML generally used for saving and exchanging office documents.Protocol: - protocol is a set of rules which governs the flow of data in network

Protocol used for sending and receiving e-mail  are SMTP, IMAP

Protocol used to transfer e-mail from mail server to client computer is POP to read the e-mail offline

Topology: - topology refers to interconnection of nodes in network.

Examples of  free webservers         1. Apache tomcat  2) XAMP 3) My SQL Server  4)WAMP  5) LAMPExample of client side scripting language  1. Java scriptExample of client side scripting language  1. JSP  2. ASPVb script is example of both client side and server side scripting languageDifference between client side script and server side script

Client side	Server side
1.       Depends upon the efficiency of client computer	1.       Do not Depends upon the efficiency of client computer
2.       It is faster than server side as it executes on local machine,	2.  It is slower than clent side script as it executes in server
3.       Does not depend on the speed of network	3. Depend on speed of network
4.       Ex. Verification of data filled in form	4.  verification of password for login

Virus : it is a malicious programme viruses, which require an infected host file to spread,

Worms: worms are standalone software and do not require a host program or human help to propagate. Worms can replicate themselves

Trojan horse: The Trojan Horse, at first glance will appear to be useful software but will actually do damage once installed or run on your computer. 

Trojans are also known to create a backdoor on your computer that gives malicious users access to your system, possibly allowing confidential or personal information to be compromised. Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate.

Computer worms are similar to viruses in that they replicate functional copies of themselves and can cause the same type of damage. In contrast to viruses, which require the spreading of an infected host file, worms are standalone software and do not require a host program or human help to propagate.

Open-source software (OSS) is computer software with its source code made available with a license in which the copyright holder provides the rights to study, change, and distribute the software to anyone and for any purpose.

GNU LINUX, LIBRE OFFICE

Free software: Free software is software that gives you the user the freedom to share, study and modify it. 

·         Freedom 0: The freedom to run the program for any purpose.

·         Freedom 1: The freedom to study how the program works, and change it to make it do what you wish.

·         Freedom 2: The freedom to redistribute and make copies so you can help your neighbor.

·         Freedom 3: The freedom to improve the program, and release your improvements (and modified versions in general) to the public, so that the whole community benefits

Ex:- GNU, Apache, Mozila

Freeware is copyrighted computer software which is made available for use free of charge, for an unlimited time. Authors of freeware often want to "give something to the community", but also want to retain control of any future development of the software.

Shareware:-  software that is available free of charge and often distributed informally for evaluation, after which a fee may be requested for continued use. Ex  Adobe , winzip, internet download manager

Freeware	Shareware
Freeware refers to software that anyone can download from the Internet and use for free	Sharewares give users a chance to try the software before buying it.
All the features are free.	Most of the times, all features are not available, or have limited use. To use all the features of the software, user has to purchase the software.
Freeware programs can be distributed free of cost	Shareware may or may not be distributed freely. In many cases, author’s permission is needed, to distribute the shareware.
Adobe PDF, Google Talk, yahoo messenger, MSN messenger	Winzip, winrar, RECUVA data recovery software

4 marks question from data communication and networking

Following question may be asked  for 1 marks each

1. Draw the best possible layout/ layout’s for the given details (no of computers in each department and distance between different department)
2. To place the server in most suitable place
3. To place the switch/hub and repeater in different department
4. Best suitable medium either guided(wired) or unguided(wirelesee)
5. Types of network used in connecting the departments
6. Types of link to create line between different department

Trick to solve the questions

1.       To draw best layout

Suppose distance between department A,B,C and d is as follows

A -B	40		NAME OF DEPT	NO OF COMPUTER
A – C	35		A	45
B - C	60		B	50
B – D	70		C	30
C- D	45		D	100
A –D	20

STEP 1; select the group which has minimum distance

Here is A –D

DRAW ACONNECTION BETWEEN A-D

A                    D

NOW SEARCH  MINIMUM DISTANCE FROM REST GROUP HAVING ‘A’ OR  ‘D’

FROM BOTH 35 IS MINIMUM HENCE TAKE THIS GROup

IF WE SEE HAVING GROUP D THEN(B-D 70, C- D 45) MIN IS 45

NOW CONNECTION WILL BE

C                                     A                             D

NOW ONLY B IS LEFT SEARCH MINIMUM DISTANCE FROM GROUP  HAVING B

(A –B, 40 B-C ,60) MIN IS 40 NOW CONNECT B FROM A NOW DIAGRAM WILL BE

(DONT FORGET TO  WRITE THE  CONCERNED DISTANCE IN ARRAOW MARK

1.       TO PLACE THE SERVER IS MOST Easy question

Server should be placed where the number of computers is maximum

Here most suitable place will be  ‘D’

2.       To place switch/Hub and repeater

Switch/hub should be placed in each department as it is used connect compute in local network, repeater can be used here distance between two department is near about hundred

In this example no repeater is required

3.       Types of network

Distance which can be considered under lan is 100mtrs

Distance within a city  can be considered under MAN

Accept above two all other connection will be considered as WAN

4.       To use of medium

Wired media

If speed does not matter and cost is to be minimized use twisted pair cable

If we need optimum performance then use co-axial cable

If cost does not matter and high speed is required use optical fibre

Wireless connection

Small plane area  use microwave

Small hilly area use radio wave

If distance is more use satellite communication

5.       To link between department/types of internet connection

1.       For low speed  dial up connection

2.       For high speed link use Broad band connection

Important questions:

1)      Write difference between GSM and CDMA

2)      Write difference between HTML And DHTML

3)      What is client side scripting and server side  scripting?

4)      Write example of client side script and server side script

5)      What is web 2.0

6)      Write example of open source  web server

7)      What is bandwidth?

8)      Write about evolution of internet