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.