Week 3: Clear

Graphic 1: A Network

How to transmit data via the internet

Computers have become an essential part of our business environment of almost everyone’s live. However, just having a standalone computer is not as beneficial as connecting computers with each other. Therefore, it is recommendable to create a network in order to communicate with each other and share resources such as databases, servers or electronic devices (e.g. printers).

Graphic 2: The Internet

There are different kinds of networks, but the most well-known network is the Internet. The communication between computers via the internet takes place with the help of internet protocols (short IPs), which define how to send data across the internet. In order to be able to send data from a sender to a receiver, it is necessary to have an Ethernet package and an IP packet, and to know the IP address. The following will explain how it is possible to send data from one computer to the other with the help of an illustrative example.

Graphic 3: IP packet in Ethernet packet

Imagine you are in Europe and you want to send a gift to a friend in the US. This present represents the so called IP payload, so the actual content or data you want to send. In order to be able to send this gift, you will put into a packet. This packet is called IP packet.This IP packet will consist of an IP header and an IP trailer. The IP header stores the information about the source and the destination, the IP addresses of sender and receiver. IP addresses specify where the computers of sender and receiver are located.  So in our example this would be the sender’s (your) and the receiver’s (your friend’s) physical address. 

If the total payload does not fit into one IP package, the payload can be split and send in fragments. Sticking to the example, if the present is too big to put it into one box, you can split it and put it into different boxes. In this case the IP header will also contain information about the fragmentation number, information about the number of boxes you send, in order to enable the receiver (your friend) to reassemble the payload (the present). 

The IP trailer contains the information about when the IP packet ends. So if you bring this IP packet to the post, the post will take it and put it onto a transport medium such as a truck or plane. The transport medium in our example is equivalent to a transmission medium, which is called Ethernet package. This Ethernet package consists of a header and a trailer. The header can e.g. contain the MAC address and the trailer contains information about when the Ethernet package ends.

This whole process of putting one packet into another, so in our case putting an IP packet with IP payload (a packet with a present) into an Ethernet package (a transport medium) is called encapsulation.

If the whole process of encapsulation and assigning the addresses is done correctly, it is most likely that the packet will arrive at the receiver, when it has been sent. However, there is no guarantee that the packets will get to its destination as the process is only based on the best effort principle. This is comparable with the promise of the post to deliver your package correctly. Although it promises to put in its best effort and resources to ensure that your packet arrives, there are still incidents when a packet will not arrive at the receiver or will arrive damaged. The same can happen in the internet. Data packets can get lost or can be delivered damaged. Hence, it is important to note that highly confidential data like credit card details should not be send via an IP packet, but rather via a TCP packet. 

TCP stands for transmission control protocol and follows the guaranteed effort principle. It is comparable to “special handling” at the post. The difference between IP and the TCP is that TCP employs another layer in the layers, so another packet in the IP packet. 

Whereas IP might have sounded familiar to you, you might have thought, when you read about TCP, that you have never come across it, but keep in mind that every time when you send confidential data to your bank or whenever you need e.g. credit card details online, most likely you might have used a TCP to send this data.

Concluding one could say, that dependent on the type of data you have, different types of transportation or more precisely, different types of transportation and packaging are used. However, it does not matter if IP or TCP is employed the process of encapsulation stays quite similar.

Graphic 1 by Mauro Bieg on commons.wikimedia.org

http://commons.wikimedia.org/wiki/File:Server-based-network.svg

Graphic 2 by Bjelli on commons.wikimeida.org

http://commons.wikimedia.org/wiki/File:Handbuch_Webdesign-InternetDatenaustausch.jpg

Graphic 3 by Nina Maria Scherl