TCP/IP architecture – Simply really!


I am now in week 7 of my Internet History, Technology and Security course with Coursera. I decided to do the optional assignment for extra grades. I didn’t do it for the extra grade, although, this will be useful, but to gain some level of understanding. Or should I say understanding full stop. This course is fascinating and whilst it claims not to be too technical, I am finding some parts very much so. I have loved hearing the stories about the early days of the internet from the people that were there. I am also interested in hearing about some of the technical aspects but I struggled in parts with the TCP/IP architecture which we have been looking at. I am determined to get some sort of grip on it and I think I get it. Sort of! Anyway, here it is. If there are any geeks (and I mean that in a good way) who want to correct any of the text below feel free. But just make sure it’s done in words of one syllable or less!

Assignment: Choose an element or aspect of the TCP/IP architecture and write a simple essay explaining how it works to a non-technical person. Do not reuse an example from the lectures in the class – come up with your own example. Your essay should choose one (or more) technical terms like “CSMA/CD”, “DHCP”, “InternetNetwork Layer”, or anything else from the topics in the class. Explain how the concept you have chosen functions in a way that someone not taking the class could understand what we are talking about. This is about writing for a non-technical audience.

In the early days of the “internet” a store and forward method was used for transmitting data. This basically is what it says. A message was forwarded and then stored and then it would be passed to the next computer, stored and forwarded and so on until it reached its destination. It was a bit like hopping across a river on stepping stones. Obviously the wider the river (or the greater the geographical distance) the more jumps were required and it took longer to reach the other side. Or in the case of the message the longer it took to get to the final destination computer. If there are lots of people (or messages) wanting to cross the river they have to wait until the previous person (message) reaches the other side. It is a lonely journey as the person jumping from stone to stone is doing so on their own. No networking here!

Academics knew there had to be a more efficient method of getting people across the stones and after many years of research they came up with packet switching. Packet switching basically meant that information was broken up in to small parts and sent across the network, which sped up the process and meant people jumped over the stepping stone more quickly (although chopped up in pieces and sent across different routes. Don’t worry they were put back together at the other end!)

So all these packets of data are jumping all over the place to get across buildings, states, countries etc. They are going through various servers and computers so that’s a lot of jumping around and potentially very complex. How could it be simplified? Easy really. Break it up (Internet researchers seem to enjoy breaking things up!)

As a result TCP/IP architecture was built. It’s full title is Transmission Control Policy/Internet Protocol and it is essentially responsible for telling the data what to do including how it should be addressed, formatted, the route it takes and how it is received at the final destination. There are four layers and each has an important job to do, the layers are:

The link layer contains communication technologies for a local network.
The internet layer (IP) connects local networks, thus establishing internetworking.
The transport layer handles host-to-host communication.
The application layer contains all protocols for specific data communications services on a process-to-process level. For example, HTTP specifies the web browser communication with a web server

For the purpose of the assignment I will be explaining the Link Layer. This is is the first of the stepping stones, the first layer in the TCP/IP architecture. It only concerns itself with the data jumping from one stone to the next (from one computer to another) at the host end. The devices (computers, printers etc) connected at the link layer is what is known as a network. Ethernet and wireless are the most common forms of link layers. The link layer basically looks out for the devices and the subsequent data only in it’s neighbourhood (network). It doesn’t care if there is a big wide world (the Internet) out there it is only worried about it’s own house and immediate neighbours within the neighbourhood. The distance between neighbours may be great or small, but it is still only the one step that the link layer is concerned with.

The link layer may have to think a bit if there is another device connected to the same network. How will the connected computers share the same network for example. What if there are 5 computers sharing the same network? If 2 of them want a conversation that isn’t meant for the other computers sharing the same “wire”, how do they do that? What about sending information whilst another computer is sending information? How do they ensure there isn’t a crash? If a computer wants to send data the link layer will have to consider how it is going to be carried during the jump. These are all the things that the link layer needs to consider. Once it’s issues have been addressed it doesn’t worry about any other aspect, it leaves this to the other layers. And this is the beauty of the system. It’s complex but each layer has it’s own job which it needs to focus on and this what simplifies data transmission.
There is obviously a whole lot more at work here but the aim of the assignment was to keep it simple. Besides this is the extent of my knowledge and even with additional reading my brain refuses to take in any more!

Image by Jelene Morris


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