Basic Network Tools: a. traceroute: A traceroute (tracert) is a command which traces the path from one network to another. Syntax: tracert hostname where hostname is the name of the server connection you are testing.

Example: tracert cbse.nic.in b. ping : ping command to test the availability of a networking device on a network.

If you receive a reply then the device is working OK , if you don’t then the device is faulty, disconnected, switched off, incorrectly configured. Syntax: ping IP address Example: ping 192.168.0.1 c. ipconfig : Displays all current TCP/IP network configuration values and refresh Dynamic Host Configuration Protocol and Domain Name System settings. Syntax: ipconfig Example: ipconfig d. nslookup : The nslookup (which stands for name server lookup ) command is a network utility program used to obtain information about internet servers. It finds name server information for domains by querying the Domain Name System.

Syntax: nslookup domainname Example: nslookup www.cbse.nic.in e. whois : whois is a simple command -line utility that allows you to easily get information about a registered domain. It automatically connect to the right WHOIS server, according to the top-level domain name, and retrieve the WHOIS record of the domain. It supports both generic domains and country code domains. Syntax: whois domainname

Example: whois amazon.in Note : Run this command after nslookup or along with nslookup command.

f. speed-test : To test the internet speed using command prompt, firstly you need to install the following using pip command. pip install speedtest-cli After successfully installation of above, run the following command. speedtest-cli

Application Layer:

The application layer contains a variety of protocols that are commonly needed by users. It provides a user interface that enables users to access the network and various services.

HTTP (HyperText Transfer Protocol): It is a protocol used t o transfer the hypertext pages over internet.

HTTP is implemented in two program: Client program and Server program. Both the programs executing on different end system, communicate to each other by exchanging HTTP messages.

Fig : Client-Server HTTP communication

E-Mail (Electronic Mail):

E-Mail is a method to send the messages in digital form. E-mail is a message that may contain text, files, images, or other attachments sent through a network to a specified individual or group of individuals.

SMTP (Simple Mail Transfer Protocol) is a protocol which is used to transfer the e-mail from sender side. This protocol is known as push protocol.

POP3 (Post Office Protocol version 3): This protocol is used to access e-mail from the server to receiver. This protocol is known as pull protocol.

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

Secure Communication:

Encryption and Decryption:

Encryption: To convert a plain text (readable) into cipher text (Non-readable).

Decryption: To convert a cipher text (Non-readable) into plain text (Readable).

Fig: Encryption and decryption

HTTPS (HyperText Transfer Protocol Secure):

It is a variant of HTTP that adds a layer of security on the data in transit through a secure socket layer (SSL).

HTTPS enables encrypted communication and secure connection between a remote user and the primary web server.

HTTPS encrypts every data packet in transition using SSL encryption technique to avoid intermediary hackers and attackers to extract the content of the data.

Digital certificate: A digital certificate is issued by a certification authority (CA).Digital certificates are used with self-signatures and message encryption. Digital certificates are also known as public key certificates or identity certificates.

Network Applications:

Remote Desktop: Remote desktop is a program that allows a user to connect to a computer in another location, see that computer's desktop and interact with it as if it were local. Example: Team Viewer, Any desk, Virtual Network Computing, GoToMyPC etc.

Remote login: A login that allows a user’s computer to connect to a host computer via a network and to interact with that host.

FTP (File Transfer Protocol): It is used to transfer files from one computer to another computer.

SCP ( Session Control Protocol): It i s a session layer protocol. It creates multiple light-duty connections from a single TCP connection. It uses Secure Shell (SSH) for data transfer.

SSH ( Secure Sh ell): Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Secure Shell provides strong authentication and encrypted data communications between two computers connecting over an open network such as the internet.

VoIP (Voice over Internet Protocol): It is the phone service over the Internet.

NFC (Near Field Communication ): NFC is a short-range high frequency wireless communication technology that enables the exchange of data between devices over about a

10 cm distance.