4write down the process for transferring data on the internet
Answers
A very basic rule of data (files, e-mails, web pages et-cetera) transmission across the Internet, and actually a distinctive feature of the TCP/IP protocols used to move data, is that data is never transmitted “as such”. Instead, it is subdivided in so-called “packets” before transmission. The number of the packets depends on the size of the data. For simplicity, let us think about the transmission of a text file. The bigger the file, the more packets will be needed to “represent” the file.
If we picture a file as a train, the packets would be the individual wagons. Big train: several wagons, small train: few, maybe just one wagon.
Each packet is like an envelope sent by normal mail, with the actual data, part of the original file, inside. Outside, we have information that will allow TCP/IP to process the packet by extracting and merging it’s inside data with the data from the other packets from the same file, in the correct order, in order to rebuild the file from it’s packets.
A very basic rule of data (files, e-mails, web pages et-cetera) transmission across the Internet, and actually a distinctive feature of the TCP/IP protocols used to move data, is that data is never transmitted “as such”. Instead, it is subdivided in so-called “packets” before transmission. The number of the packets depends on the size of the data. For simplicity, let us think about the transmission of a text file. The bigger the file, the more packets will be needed to “represent” the file.
Figure 1-1-1: Representation of a TCP/IP packet – Source: Wikipedia
If we picture a file as a train, the packets would be the individual wagons. Big train: several wagons, small train: few, maybe just one wagon.
Each packet is like an envelope sent by normal mail, with the actual data, part of the original file, inside. Outside, we have information that will allow TCP/IP to process the packet by extracting and merging it’s inside data with the data from the other packets from the same file, in the correct order, in order to rebuild the file from it’s packets. A scheme of a TCP/IP packet is shown in Figure 1-1-1)
Each packet, or envelope if we follow on the previous example, contains the following information: the source of the data (sender), the destination of the data (receiver), information on the source file and on the position of the packet in this file (say packet 3 of 123 from file X). With this information, once all the packets for a file have reached the intended destination, they can be used by TCP/IP to rebuild the original file.
We could summarize the journey of a file such as an e-mail message or a web page, from computer A to computer B, as follows.
File in computer A –> Subdivided in packets by TCP/IP –> Packets travel, individually, to destination –> TCP/IP “remounts” the packets to re-create the original file in computer B –>File in computer B
You may notice, in the scheme above, that the fact that packets travel individually is underlined. As we mentioned, communication paths (most often constituted by physical wires) between computer A and computer F (Figure 1-1) on the Internet are often redundant. Also, these paths are often not direct (unless A and F are in the same room or the same building), but rather contain a number or “relays”. That is, in order for data to travel from A to F, they might be relayed through B, C, and D (Figure 1-1). Physically, on the hardware level, there relays are constituted by Routers. As the name implies, routers allow packets to find the best route between two computers that do not belong to the same network. Data are generally relayed through several such routers before they reach their final destination.