What is HTTP and HTTPS protocol ?

HTTP is the HyperText Transfer Protocol which defines the set of rules and standards on how the information can be transmitted on the World Wide Web (WWW). It helps the web browsers and web servers for communication. It is a ‘stateless protocol’ where each command is independent with respect to the previous command. HTTP is an application layer protocol built upon the TCP. It uses port 80 by default. HTTPS is the HyperText Transfer Protocol Secure or Secure HTTP. It is an advanced and a secured version of HTTP. On top of HTTP, SSL/TLS protocol is used to provide security. It enables secure transactions by encrypting the communication and also helps identify network servers securely. It uses port 443 by default.

What is SMTP protocol ?

SMTP is the Simple Mail Transfer Protocol. SMTP sets the rule for communication between servers. This set of rules helps the software to transmit emails over the internet. It supports both End-to-End and Store-and-Forward methods. It is in always-listening mode on port 25.

TCP and UDP protocol, prepare differences

TCP is a connection-oriented protocol, whereas UDP is a connectionless protocol. A key difference between TCP and UDP is speed, as TCP is comparatively slower than UDP. Overall, UDP is a much faster, simpler, and
efficient protocol, however, retransmission of lost data packets is only possible with TCP.

TCP provides extensive error checking mechanisms. It is because it provides flow control and acknowledgment of data. UDP has only the basic error checking mechanism using checksums.

What happens when you enter “google.com” (very very famous question)

Check the browser cache first if the content is fresh and present in the cache display the same.
If not, the browser checks if the IP of the URL is present in the cache (browser and OS) if not then requests the OS to do a DNS lookup using UDP to get the corresponding IP address of the URL from the DNS server to establish a new TCP connection.
A new TCP connection is set between the browser and the server using three-way handshaking.
An HTTP request is sent to the server using the TCP connection.
The web servers running on the Servers handle the incoming HTTP request and send the HTTP response.
The browser processes the HTTP response sent by the server and may close the TCP connection or reuse the same for future requests.
If the response data is cacheable then browsers cache the same.
Browser decodes the response and renders the content.

Hub vs Switch

Hub: Hub is a networking device which is used to transmit the signal to each port
(except one port) to respond from which the signal was received. Hub is operated on a Physical layer. In this packet filtering is not available. It is of two types: Active Hub, Passive Hub.

Switch: Switch is a network device which is used to enable the connection
establishment and connection termination on the basis of need. Switch is operated on the Data link layer. In this packet filtering is available. It is a type of full duplex
transmission mode and it is also called an efficient bridge

VPN, advantages and disadvantages of it

VPN (Virtual Private Network) : VPN or the Virtual Private Network is a private WAN
(Wide Area Network) built on the internet. It allows the creation of a secured tunnel
(protected network) between different networks using the internet (public network). By using the VPN, a client can connect to the organisation’s network remotely.

Advantages of VPN :
1. VPN is used to connect offices in different geographical locations remotely and is
cheaper when compared to WAN connections.
2. VPN