The History About The Network Layer

Published Date: 02 Nov 2017

Abstract:

The project will use the program wDigipet, a widely known software used to simulate train routes and orders specifically onto model trains, in order to try and test a futuristic way of transforming the train network, where conductors and switches / lights workers could become obsolete since everything would be controlled from the central hub. The report will show how through the use of the decoders on trains, switches and lights, it will be possible to control, the movement of the locomotors, and timings in which they will get into the wanted tracks. Throughout the project it will be shown how with the simple use of ip addresses all of the previously mentioned can be easily done through the use of one main server.

Introduction

Networks are the backbone to the IT world, and the reason why we can communicate with people all over the world through the internet. Before we had networks it was very difficult to communicate with people from your place of work, or house to somewhere else without needing to send someone else to communicate, or without going yourself. In train stations especially more people where needed just in order to direct railway traffic, and everything had to go according to plan, because notifying took even more time. Now instead all trains, switches and lights are tagged with a set ip, in order to identify them, and a man behind a computer can control hundreds of train destinations, and timings into the stations, with the simple click of a mouse. Unfortunately most times, even with the IT networks implemented, it is very time consuming and costly to fix any problems directly unto the network as you never know if the fix will work or not and that is why simulations come into play. Simulation is nearly essential these days, it saves companies and engineers a ton of money, by testing out their networks before actually implementing them in real life. Another really important part of simulations in networks is the ability to perfect a protocol beforehand without needing to rebuild the whole network, while it’s working. There are different possibilities of simulator that can be used to create a simulation of a network, and a lot of them give you loads of information that cannot be found straight away from working directly onto the track.

Objectives and Difficulties

The aim of the project is to show how in the future overground trains, railroads, will be able to match their brothers in the underground having the possibility of running unmanned, all controlled through a central computer hub. This will be done through the software wDigipet, through which it will be shown how by using decoders on trains, switches and lights it is possible to give each sector an ip address, from which it is possible to control everything from the server. The hardest part of the project will be to implement what is done on the software onto a train plastic, to show how it could properly work, and to be able to control perfectly everything on it. The other difficulty in the project will be into properly learning to use the wDigipet software to the maximum, and possibly adding more and more obstacles to the circuit as the confidence with the software increases.

THE TRANSPORT SYSTEM

In the transport system, a vehicle’s pace is constrained from other vehicle’s on its path, and it is therefore needed that the driver keeps enough distance for him to be able to react in time in case the preceding vehicle’s slows down or stops. Maintaining this distance may be done autonomously by the driver through the information in his possession thanks to his vision, giving him the possibility to choose the best speeds and manoeuvres, or it can be kept by conveying from the outside to the driver, through the use of proper signs and instruments, instructions on which speeds to keep and which manoeuvres to do. These are the two types of paces that a train can partake, by sight or by external instruments. Railroads are mostly an example of pace by external instruments as the driver is obliged to follow the signals given to them through visual and acoustic, in order to decide the pace to keep, while automobile drivers instead rely on their vision in order to decide how much distance, and pace to keep.

SIGNALS and Security

Since the start of the railways with wooden rails to the upgrade into iron rails, that started in England the 1860s, safety was a major problem with railways. Initially there were no safety measures and everything was based on the discretion of the driver and how well he would react to what happened around him. The problem with keeping pace by vision, on railroads is the massive amount of weight that the locomotive is transporting; therefore there is a bigger possibility of error within breaking, as more distance is needed. It also become a big problem to use pace based on sight, once the railroad traffic started to intensify as it increased the likelihood of human error. That is why signals, and other measures of security were started to be added, and as times went on more solid and stable materials were used to build trains and railroads such as steel. The second point in safety that had to be sorted out, was to make sure that two or more trains could go through a railway track without crashing against each other, and even though initially this was done through the use of workers that would signal drivers to slow down for incoming traffic, station or any other difficulty, it soon meant the addition of signals/lights and switches.

This was initially done through the use of fixed signals, and the importance of these fixed signals was how all the drivers would know the positions of these and therefore stop or slow in order to check them. The way it was done to tell a train to stop for whatever reason was to add a red flag to the signal, and usually a red lamp as well so that it was possible to see it during the night. The next stop was to add rotating flat shapes to these fixed signals in order to be able to signal both stop and go without needing to go and take down the flag or lamp, in fact the shapes could just be rotated in parallel to signal the good to go, while if they were perpendicular meant for the train to stop. Colours played a big part in it as well; red was always a colour of stop or danger, and white of safety, while in America blue was chosen as the colour for safety. The problem with the different colours was that they were sometimes hard to see from a distance and a change was therefore needed in order to solve this problem. The first to do so was the Caledonian Railway in the 1850’s, which created signals that had different shapes to mean different things. A ticket was added to the vane, and when it was facing away from the track it meant Caution while if it faced the tracks it meant Danger, naturally these were both usually coloured really bright in order to be able to see them through certain weather conditions like fog. Vane signals have been a very important of railroads, especially in certain countries like France where they were used until the 1900’s.

SOFTWARE

TCP IP

The Transport Control Protocol / Internet Protocol also known as TCP/IP is the simplest and most used network protocol around right now. There are two different ways accepted of showing the OSI (Open Systems Interconnection) model, one where it has five layers, and the other one where it has seven layers. The model is divided between Application, transport, network, link and physical layers. The two models are basically identical, where the only difference is the addition of the Presentation and Session layers, in the seven layer model, where in the more basic five layer one they are considered part of the Application part. These two layers are added in order to further distinguish all the different protocols that can be used within the Application Layer.

Application Layer

Each layer has a different purpose and different protocols; the application layer mostly takes care of most of the applications of the network, examples of protocols are FTP, TFTP and HTTP (File Transfer Protocol, Trivial File Transfer Protocol, Hypertext Transfer Protocol), the application layer also expects a service from the transport layer, but since it is at the top of the model it doesn’t need to service any other layer, so it just worries about using the protocols, it has to fulfill the wishes of the user. File Transfer Protocols is one of the oldest protocls to have been created and it is sometimes believed that the internet was in fact created in order to be able to transfer files between nodes and computers in a network and it is therefore one of the most important protocols. Throughout the years the suite has evolved and now the FTP or TFTP can be substituted with messaging protocols, where files are transferred through attachments of these rather than uploaded to a server to then be used by others computers that access that same server. How FTP works is that through a Graphical User Interface (GUI), the user can see what files the

server stores and with a couple of clicks it can decide which ones to download to their network, or which ones to delete from the server completely. Once a file has been chosen then a connection will be established to move the data from the server to the end user computer, and in order to assure that the data arrives protocol asks for the help of the TCP from the transport layer.

The Transport Layer

The transport layer does service to the application layer, and expects service from the network layer, many of the services that its protocols provide are Reliable Delivery of data, Multiplexing / Demultiplexing and flow and congestion control. The two main protocols used within this layer are TCP and UDP (Transmission Data Protocol and User Datagram Protocol). The TCP can perform all three of the services stated earlier, while the UDP can only perform Multiplexing and Demultiplexing. The difference between the two protocols is quite big, but they are both essential to the perfect functioning of the transport layer. Initially the transport layer was built with only the TCP, but it was later seen that a single protocol could not handle all the work that needed to be done with great efficiency, so UDP was created. While the TCP makes sure that packets can be sent to through a connection to the same address, and makes sure connection can be established between two devices. The UDP instead is a protocol, which is based on speed, and gives the possibility for applications to access the IP, without the need of an internet connection and therefore bypassing a lot of obstacles that slow down the process, in the TCP. Another main difference between UDP and TCP is the way packets are sent, UDP sends one packet at a time, while TCP sends a stream of packets, this means that packets sent in UDP aren’t missing anything and can be stored straight away.

The Network layer

The network layer is often referred to as the internet layer, and the main job of its protocols is to connect the network together as well as dealing with the routing part of the network. The main protocol used within this layer is the IP (Internet Protocol). The IP is an address protocol that identifies the point of the machine, and it is based on location rather than on machine, depending on where the user is in the world the IP will change, differently from the MAC address that

remains the same for the computer used, no matter where in the world it is situated. The IP is divided into two different types of the protocol, the IPv4 and the IPv6. The IPv4 are 32bit long addresses while the IPv6, are 128bit long addresses. As of right now the IPv4 is the most commonly used one, as being smaller it easier to use, and because most networks are already configured for it. The problem though is that as the years keep passing the number of available IPv4 addresses are finishing and there has to be a moment where a 100% switch will need to be made to the IPv6 in order to have the possibility to give everyone in the world an IP address.

The Data link layer consists mostly of the user part of the network and everything to do with the Operating Systems and drives and part of the pc that has to do with where the packet is going to end up. An example of a protocol within this layer is the PPP (Point to Point Protocol). The last layer is the physical layer, and it consists with the communication part of the network, things such as wireless, radio waves and how data will be transferred.