Internet data transmission

To understand how data is transmitted through the internet, the internet networking structure works must first be examined. The internet is a large network of devices that are each assigned an address otherwise known as an Internet Protocol or IP. So how do computers utilize their individual IPs to communicate with each other? Let’s provide an example, say a computer’s IP address is 2.2.2.2 and it wants to send a message to a computer that has an IP address of 3.3.3.3. To do this first the message must be turned from alphabetic text into electronic signals using the protocol stack.

The protocol stack is the IP/TCP protocol that is built into a computer’s OS to help it communicate with the internet. Below is a general overview of the layers within a protocol stack.

Here is an overview of how this protocol stack would work from a Stanford Networking class.

  1. The message would start at the top of the protocol stack on your computer and work it’s way downward.
  2. If the message to be sent is long, each stack layer that the message passes through may break the message up into smaller chunks of data. This is because data sent over the Internet (and most computer networks) are sent in manageable chunks. On the Internet, these chunks of data are known as packets.
  3. The packets would go through the Application Layer and continue to the TCP layer. Each packet is assigned a port number. Ports will be explained later, but suffice to say that many programs may be using the TCP/IP stack and sending messages. We need to know which program on the destination computer needs to receive the message because it will be listening on a specific port.
  4. After going through the TCP layer, the packets proceed to the IP layer. This is where each packet receives it’s destination address, 5.6.7.8.
  5. Now that our message packets have a port number and an IP address, they are ready to be sent over the Internet. The hardware layer takes care of turning our packets containing the alphabetic text of our message into electronic signals and transmitting them over the phone line.
  6. On the other end of the phone line your ISP has a direct connection to the Internet. The ISP’s router examines the destination address in each packet and determines where to send it. Often, the packet’s next stop is another router. More on routers and Internet infrastructure later.
  7. Eventually, the packets reach computer 5.6.7.8. Here, the packets start at the bottom of the destination computer’s TCP/IP stack and work upwards.
  8. As the packets go upwards through the stack, all routing data that the sending computer’s stack added (such as IP address and port number) is stripped from the packets.
  9. When the data reaches the top of the stack, the packets have been re-assembled into their original form, “Hello computer 5.6.7.8!”

But what’s in between two devices that are communicating with each other? The internet is composed of a multitude of networks that are all linked together. These large network service providers often sell bandwidth to smaller networks, which results in a large and complex hierarchy of networks.

Sources:

https://web.stanford.edu/class/msande91si/www-spr04/readings/week1/InternetWhitepaper.htm

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