HTTP and HTML

When an address is typed into a browser, the browser establishes a connection to the web service running on the server. The protocol for establishing a connection is HTTP. HTTP means HyperText Transfer Protocol. Hyper Text Transfer Protocol is the basic protocol used by the World Wide Web. This protocol defines how messages are formatted and transmitted, and what actions should take by Web servers and web browsers in response to various commands.

The URL(Uniform Resource Locator) and URI(Uniform Resource Identifier)  are the names the majority people used with the web addresses. If we want to open a web address http://fschub.com/ccna-study-guide.html   we can examine how an address is opened in the browser.

1. Protocol - HTTP


2. Server Name - fschub.com


3. The Specific filename which is requested ccna-study-guide.html

As shown in Figure, entering the mentioned URL in the browser, the browser then checks with a name server to convert fschub.com into a numeric IP address, which it uses to connect to the server. The browser then sends a GET request to the server using HTTP and asks for the ccna-study-guide.html file. The server then sends the HTML code of this particular page to the browser. In conclusion, the browser read the HTML code and formats the page for the browser window and show it to the user. The HTML is the main standard that controls how the World Wide Web works. It covers how the Web pages are formatted and displayed at the user screen.

HTTP and HTTPS

HTTP is a request/response protocol. When a client, sends a request to a web server, the protocol which specifies the message type is HTTP. There are three common message types are GET, POST, and PUT.

GET - A host request for data, generally a webpage request

POST - Uploads data files to the web server

PUT - Uploads resources or content to the web server such as an image, video, and audio.

Hypertext transfer protocol is extraordinarily protocol but it is not secure. The HTTP send request messages to the server in plain text that can be intercepted and read anywhere in the way. The responded HTML pages are also in unencrypted and unsecured pages.

To secure communication across the internet the HTTPS protocol is used which is too secure from Hypertext transfer protocol. This protocol uses authentication and encryption to secure data traveling between the client and server. it uses the same client request-server response process as HTTP; but the data travel between client and server is encrypted with SSL (Secure Socket Layer)

TCP/IP Communication Process

Figures 2-2 show the complete communication process using an example of a web server transmitting data to a client. This process and these protocols will be covered in more detail in later chapters.

1. Web server is sending data using Hypertext Markup Language (HTML) page to be sent to web clients.

2. The application protocol HTTP header is added to the front of the HTML data. The header contains a variety of information just like IP header, Ethernet header, TCP header as well as the HTTP version the server is using and a status code representing it has information for the web client.

3. The HTTP application layer protocol forwards the HTML-formatted web page data to the transport layer (Layer 4 of the OSI Model). The TCP transport layer protocol is used to handle individual conversations; in this example between the web server and web client.

4. Next, the IP information is added to the front of the  TCP information. IP assigns the appropriate source and destination IP addresses. This information is known as an IP packet.

5. The Ethernet protocol adds information to both ends of the IP packet; known as a data link frame. This frame is delivered to the nearest router along the path towards the web client. This router removes the Ethernet information; analyzes the IP packet; determines the best path for the packet; inserts the packet into a new frame; and sends it to the next neighboring router towards the destination. Each router removes and adds new data link information before forwarding the packet.

6. This data is now transported through the internetwork; which consists of media and intermediary devices.

7. At the receiving end, the client receiving the data link frames that contain the data. Each protocol header is processed and then removed in the opposite order it was added. After removing all headers the user received and see the original data.