Difference between HTML and HTTP? HTTP and HTTPS? HTTP and FTP?

Difference between HTML and HTTP

HTML (Hypertext Markup Language) is a language for marking the normal text so that it gets converted into hypertext. Basically, HTML tags (e.g., “<head></head>”, “<body></body>” etc.) are used to tag or mark normal text so that it becomes hypertext and several hypertext pages can be interlinked with each other resulting in the Web. Note here that the HTML tags are used to help render web pages as well in the web browser. On the other hand, HTTP (Hypertext Transfer Protocol) is a protocol for transferring the hypertext pages from Web Server to Web Browser. For exchanging web pages between Server and Browser, an HTTP session is setup using protocol methods (e.g., GET, POST etc.).

Differences between HTTP and HTTPS

· In HTTP, URL begins with “http://” whereas URL starts with “https://”

· HTTP uses port number 80 for communication and HTTPS uses 443

· HTTP is considered to be unsecure and HTTPS is secure

· HTTP Works at Application Layer and HTTPS works at Transport Layer

· In HTTP, Encryption is absent and Encryption is present in HTTPS as discussed above

· HTTP does not require any certificates and HTTPS needs SSL Certificates

HyperText Transfer Protocol (HTTP) is a protocol using which hypertext is transferred over the Web. Due to its simplicity, http has been the most widely used protocol for data transfer over the Web but the data transferred without any security protocol, it may have security attacks and data is compromised. So, to provide some security to transmission https was introduced so that a secure session is setup first between server and web browser. In fact, cryptographic protocols such as SSL and/or TLS turn http into https i.e. https = http + cryptographic protocols. Also, to achieve this security in https, Public Key Infrastructure (PKI) is used because public keys can be used by several Web Browsers while private key can be used by the Web Server of that particular website. The distribution of these public keys is done via Certificates which are maintained by the web browser. You can check these certificates in your Browser settings.

HTTP stands for Hyper-Text Transfer Protocol, FTP for File Transfer Protocol, while SMTP stands for Simple Mail Transfer Protocol. All the three are used to transfer information over a computer network, and are an integral part of today’s internet.

Difference between HTTP and FTP:

S.NO.	HTTP	FTP
1.	It stands for HyperText Transfer Protocol.	It stands for File Transfer Protocol
2.	It is the set of rules that how web pages are transferred on different computers over the internet.	It is the set of rules that permit the downloading and uploading the files on the computer over the internet.
3.	It only supports the data connection.	It supports both data connection and control connection
4.	It uses Transmission Control Protocol and runs on TCP port 80.	It uses Transmission Control Protocol and runs on TCP port 20 and TCP port 21.
5.	The URL using the HTTP protocol will start with HTTP.	The URL using the FTP will start with FTP.
6.	It does not require authentication.	It requires authentication.
7.	It is efficient in transferring small files.	It is efficient in transferring large files.
8.	The files transferred to the computer over the internet are not saved to the memory.	The files transferred to the computer over the internet are saved to the memory.
9.	HTTP is used to provide the web pages to the web browser from the webserver	FTP is used to upload or download files between client and server.
10.	It is a stateless protocol.	It is not a stateless protocol and it maintains states.
11.	It supports an In-band type of band transfer.	It supports an Out-of-band type of band transfer.
12.	It can use both types of Persistent and Non-persistent TCP connection.	It uses a Persistent TCP connection for the Control connection and a Non-persistent TCP Connection for Data Connection.

A Domain Name System (DNS) converts a human-readable name (such as www.google.com) to Numeric IP-address. The DNS system response one or more IP-address by which your computer connects to a website (such as www.google.com) by using one of the IP-address. DNS is a host name to IP address translation service. DNS is a distributed database implemented in a hierarchy of name servers. It is an application layer protocol for message exchange between clients and servers.

Requirement:

Every host is identified by the IP address but remembering numbers is very difficult for the people and also the IP addresses are not static therefore a mapping is required to change the domain name to IP address. So DNS is used to convert the domain name of the websites to their numerical IP address.

Domain:
There are various kinds of DOMAIN :

1. Generic domain: .com(commercial) .edu (educational) .mil(military) .org(non-profit organization) .net(similar to commercial) all these are generic domain.

2. Country domain .in (india), .us, .uk.

Why does DNS use UDP and not TCP?

DNS is an application layer protocol. All application layer protocols use one of the two transport layer protocols, UDP and TCP. TCP is reliable and UDP is not reliable. DNS is supposed to be reliable, but it uses UDP, why?

There are following interesting facts about TCP and UDP on the transport layer that justify the above.
1) UDP is much faster. TCP is slow as it requires 3-way handshake. The load on DNS servers is also an important factor. DNS servers (since they use UDP) don’t have to keep connections.
2) DNS requests are generally very small and fit well within UDP segments.
3) UDP is not reliable, but reliability can added on application layer. An application can use UDP and can be reliable by using a timeout and resend at the application layer.

Actually, DNS primarily uses the User Datagram Protocol (UDP) on port number 53 to serve requests. DNS queries consist of a single UDP request from the client followed by a single UDP reply from the server. When the length of the answer exceeds 512 bytes and both client and server support EDNS, larger UDP packets are used. Otherwise, the query is sent again using the Transmission Control Protocol (TCP). TCP is also used for tasks such as zone transfers. Some resolver implementations use TCP for all queries.