In this post we will continue talking about how are communications between different networks made, what elements that are used in order to communicate and how all things fit together. As we talked in the previous post http://www.ittrainingday.com/2013/01/networking-fundamentals-tutorial.html#.UO0zB2_FWwk there are some important pieces that are used in a communication. Imagine you are trying to access a web page from your personal computer. Your computer is the source or the sender of the message, the server that is hosting the web page is the destination or the receiver. Between these two elements a communicating channel is created, this is basically all elements needed to transmit the message from source to destination. In the image below I created a picture of the three components involved in a communication:
You would normally imagine that when you’re requesting a web page the message is sent and returned as a big chunk of information. Before I studied networking I didn’t understood how messages are transmitted over networks and how all the pieces fit together. That is why I want to create this tutorials in order for others that are interested in this domain, to understand the functionality of networks. When you transmit a message over a network, the actual information is divided into multiple pieces, this mechanism is called segmentation. By segmenting a message, every small piece can be transmitted independently and if a problem occurs with that particular piece, then that piece can be dropped or retransmitted. Imagine that if your message is very big, if a problem occurs than it will take more time to retransmit the whole message again, so that’s why segmentation is very useful. Another benefit is that multiple pieces of different messages can be transmitted in the same channel. This means that when you are sending information over the medium, others can transmit in the same time, this is because all the pieces are interleaved over the network, this process is called multiplexing, you can read more about multiplexing in the following link: http://en.wikipedia.org/wiki/Multiplexing. Imagine how long would it take to obtain information over networks if everyone would have to take turns in transmitting. Of course the pieces have to be reassembled at the destination, we will talk about this aspect later.
The path that the pieces travel from source to destination can change in time. The process of segmentation and multiplexing is best shown in the following image:
By now you are probably asking yourself how are the pieces reassembled at the destination if multiple pieces of information are transmitted on the same channel. Well, all the pieces that make up your message have some labels so that they are uniquely identified over the network. This way when the information arrives at the destination they can be reassembled to form the whole message.
I have told you in the previous post that the Internet is a big collection of networks that are interconnected. Every network that is connected to the Internet adds to the size of it. There are many types of networks but if we divide them by the size, the number of devices, the number of users and the geographical locations we can say that there are two main types of networks, LAN or Local Area Network and WAN or Wide Area Network. LAN’s are generally networks that are located in a single geographical area and are usually administrated from one location. An example of LAN is your home network or the network of your company where you work, a WAN is a network that has big dimensions and covers large geographical areas. Another way you can look at a WAN network is to visualize it as multiple LAN networks interconnected. The global interconnected networks is the Internet, but what is Intranet then? Well, Intranet is often described when you make reference to multiple LAN networks or WAN networks that belong to an organisation and are accessible only by it’s members. For example Microsoft’s Intranet is accessible by it’s employees and not by outside users. In the past post I have showed you the components the make up the network: end devices( such as computers,laptops,printers etc.), intermediary devices(routers,switches,hubs etc.) and the medium(UTP cable,fibre optic etc.). Beside this elements there are the ports which are physical connectors in which cables are plugged( can be a switch port, a wall port, a network card port) and network interface cards or NIC ( these are hardware devices incorporated in computers,servers,printers etc. and are used to provide physical connection with the network).
That’s it about this post, in the next one we will talk about protocols, protocol suits and the standards used in networking. I hope this was an interesting post, stay tuned for more.