2Agenda Introduction. Types of Networks. Clients and Servers. 13 April 2017AgendaIntroduction.Types of Networks.Clients and Servers.Network Topologies.Internet and Intranet.Network Hardware and Software.Review.VRM & RVT Training Program - Vehicle Familiarization
3PurposeAs part of the job you may be required to use a TTC network to perform duties such as:Remotely monitor a system.Work with data.Run diagnostics.The purpose of this course is to introduce and familiarize you with the basic aspects of computer networks and how they relate to the TTC networks.
5Introduction.NetworksTwo or more computers connected together in a way that allows resource sharing.A network contains any combination of computers, computer terminals, printers, display devices, cables, or wireless connections.A network is a collection of computers or other hardware devices that are connected together using special hardware and software. This allows them to share information and cooperate.
6Resources Resources may be: Files. Folders. Printers. Memory. Introduction.ResourcesResources may be:Files.Folders.Printers.Memory.Applications.
7Computer networking Advantages Disadvantages Introduction.Computer networkingAdvantagesDisadvantagesCommunication between computer processing units (CPUs)Access restrictionsData sharingServer failuresHardware sharingPrivacy concernsInternet accessSecurity threatsData managementRedundancy
9Types of Networks.Network typesComputer networks vary in shape (topology) and size depending on their application.Some of the major types are:Local area networks (LANs).Wide area networks (WANs).
10Local area networks (wireless and wired) Types of Networks.Local area networks (wireless and wired)Span a small geographic area.Usually confined to a building, a group of buildings, or a vehicle, for example a train or a streetcar.Data travels between network devices via network cables (LANs) or wireless signals (WLANs).The most common types are Ethernet and Wi-Fi.
11Wide area networks (WAN) Types of Networks.Wide area networks (WAN)A WAN is a computer network that covers a large area (any network whose communication links across metropolitan, regional, or national boundaries).A network that uses routers, modems, and public communication links.The world’s largest WAN is the Internet.WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations.
14Clients and Servers.ServersA server is a core component of the network, providing access to the resources.The access it provides could be to a resource existing on the server itself or a resource on a client computer.The server assigns IP addresses to each resource.
15IP addresses IP stands for Internet Protocol. Clients and Servers.IP addressesIP stands for Internet Protocol.IP addresses serve as the location of websites on the Internet as well as workstations that are connected to the network.IP addresses are made up of four sets of numbers called “octets.”There are two types of IP addresses:Static IP addresses.Temporary IP addresses.
16Static IP addresses Located on servers and do not change. 13 April 2017Clients and Servers.Static IP addressesLocated on servers and do not change.Example: The HVAC units on the Toronto Rocket have a static IP address on the Train Information Network (TIN).Car NumberHVAC positionIP address123456The table displays the IP addresses of each HVAC on each car.These do not change.Sometimes, the IP addresses must be entered manually in order to connect to a specific HVAC unit.i.e. by an SVTVRM & RVT Training Program - Vehicle Familiarization
17Temporary IP addresses Clients and Servers.Temporary IP addressesA device connected to the network is assigned a new IP address each time it is logged on.Assigned by an Internet Service Provider (ISP) each time a computer is logged on to the network.On the TIN, the Train Information Management System (TIMS) assigns a temporary IP to laptops connected to the Ethernet.
18Clients and Servers.ClientClients are computers/devices that request and receive information over a network.Client computers can also depend on the central server for processing activities.For example a laptop running diagnostics on trains.
19Client/server networking 13 April 2017Clients and Servers.Client/server networkingA client/server network is a system where one or more computer called a client connects to a central computer called a server to share or use resources.A computer network is referred to as a client/server if, at least, one of the computers is used to “serve” other computers referred to as “clients.”Many types of devices can be part of the network; e.g., scanners, printers, laptops–portable test equipment (PTE), and desktop computers.Sometimes, like in the case with TIMS, the operating system on the clients must be compatible with that on network.VRM & RVT Training Program - Vehicle Familiarization
20Client/server networking Clients and Servers.Client/server networkingIn a client/server network, each computer can store resources and files. Clients can also access resources stored on other clients.Most files and resources are centralized. This means that one computer (the server) stores them and other computers (the clients) access them.The server is always on, allowing any client to access files and resources even if the other clients (computers) are off.
21The relationship between a client and a server 13 April 2017Clients and Servers.The relationship between a client and a serverIn order to gain access to the network and other resources the client sends a request to the servers and the server will respond with a path/access to the requested resourcesVRM & RVT Training Program - Vehicle Familiarization
23Network Topologies.Network topologiesNetwork topology refers to the shape of a network, or the network’s layout. A network’s topology determines how different devices in a network are connected to each other and how they communicate.The different network topologies are as follows:Bus.Hybrid.Star.Mesh.Ring.
24Network topologies Physical topology The physical structure of the network. The layout of the cables and connections between the network components.Logical topologyDefined by the network protocols and explains how data travels across the cables.
25Network Topologies.Bus topologyAll devices are connected to a central cable, called a bus or a backbone.The simplest physical topology–least amount of cables–but also covers the shortest distance.There are terminators at each end of the bus that stop the signals and keep them from travelling backwards.All computers share the same data and address path. Messages pass through the central cable and each computer checks to see if the message is addressed to itself. If the address of the message matches the computer’s address, the network adapter copies the message to the card’s on-board memory.
26Information flow BUS TOPOLOGY 13 April 2017 The signal (yellow) leaves its source and as it travels through the central cable it passes through each connected device, however, only the addressed device is the one that will ‘accept’ the message (let the message through).Pro: Easy to set upAny break in the network central cable or either terminal will result in a total break in the network.Information flowBUS TOPOLOGYVRM & RVT Training Program - Vehicle Familiarization
2713 April 2017Network Topologies.Ring topologyAll devices are connected to one another in the shape of a closed loop.Each device is connected directly to two other devices, one on either side of it.An equivalent system exists on the trains (TIN) and on streetcars (the Streetcar Network).VRM & RVT Training Program - Vehicle Familiarization
28Information flow RING TOPOLOGY 13 April 2017 A break in one of the components won’t prevent the signals from going through.The signal can flow in the other direction to reach its destination.Information flowRING TOPOLOGYVRM & RVT Training Program - Vehicle Familiarization
29Ring topology on the Toronto Rocket 13 April 2017Example on the TR.Data/signals flow both in the clockwise and counterclockwise directionsRing topology on the Toronto RocketRING TOPOLOGYVRM & RVT Training Program - Vehicle Familiarization
30On the train: ring switch Network Topologies.On the train: ring switchContains the network software.Assigns IP addresses.Enables communication over the TIN.Routes the signals to the TIMS for monitoring.
31On the streetcar: ring switch Network Topologies.On the streetcar: ring switchContains the network software.Assigns IP addresses.Enables communication over the streetcar network.
32Network Topologies.Star topologyDevices are not directly connected to each other, rather through a central hub.Devices communicate across the network by passing data through the hub or switch.
33Information flow STAR TOPOLOGY 13 April 2017 The information flow in the star topology goes through one central point to which all devices are connected.A break in the connection between the hub and one of the components will isolate only that component, but will not affect the rest of the network.Issues with the hub itself, however, will affect the entire network.Information flowSTAR TOPOLOGYVRM & RVT Training Program - Vehicle Familiarization
34Network Topologies.Mesh topologyThe simplest logical topology in terms of data flow, and the most complex topology in terms of physical design.Each device is connected to every other device.This topology is rarely found in LANs, mainly because of the complexity of the cabling.Because of its design, the physical mesh topology is very expensive to install and maintain.The advantage you get from mesh topology is that it has a high fault tolerance.
35Information flow MESH TOPOLOGY 13 April 2017 PRO: A break in the system won’t prevent the signal from getting through, as it will find alternate routes to reach its destination.CON: However, setting up cables, connecting devices, and shouldering the costs renders the topology impractical.Information flowMESH TOPOLOGYVRM & RVT Training Program - Vehicle Familiarization
3613 April 2017Network Topologies.Hybrid topologyA hybrid topology is produced when two, or more different basic network topologies are connected (bus, star, ring).This topology is used when a new section is added to an already existing network.PRO: Highly reliableCON: But hard design and very costly to set up (cables and specialized hubs)VRM & RVT Training Program - Vehicle Familiarization
37Internet and Intranet Computer Networks 13 April 2017 VRM & RVT Training Program - Vehicle Familiarization
38Transmission Control Protocol Internet and Intranet.Internet vs. intranetInternetA worldwide system of computer networks. A network of networks in which users at any one computer, with the necessary permissions, can get information from any other computer.The most commonly used protocol is TCP/IP, it stands for:Transmission Control ProtocolInternet ProtocolTCP/IP
39Internet and Intranet.Internet protocolThe most common network protocol in public use is the IP.The basic protocol that enables home computing devices and LANs across the Internet to communicate with each other.Works well for moving individual messages from one network to another.TCP allows continuous transmission of data (streaming).The two protocols are almost always paired together and are known as TCP/IP.
40Internet vs. intranet Intranet A self-contained private network. 13 April 2017Internet and Intranet.Internet vs. intranetIntranetA self-contained private network.It may consist of many interlinked local area networks and also use leased lines in a wide area network.Uses TCP/IP, hypertext transfer protocol (HTTP) and other Internet protocols.Companies can send messages through the public network, using encryption/decryption and other security safeguards to connect one part of the intranet to another.VRM & RVT Training Program - Vehicle Familiarization
41Network/communication protocols Internet and Intranet.Network/communication protocolsA protocol is simply an agreed on set of rules and procedures for transmitting data between two or more devices. Hundreds of different protocols have been developed, each designed for specific purposes and environments.The protocol defines:How the sending device indicates it has finished sending the message.How the receiving device indicates it has received the message.How data is transmitted from source to destination.The type of error checking to be used.
42Network/communication protocols Internet and Intranet.Network/communication protocolsNetwork protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages, sent, and received.Hundreds of different computer protocols have been developed, each designed for specific purposes and environments.
4313 April 2017Internet and Intranet.Network protocolsNetwork protocols are layered such that each one relies on the protocols that underlie it. Sometimes referred to as the protocol stack.Both TCP and IP operate somewhere in the middle of a network protocol stack.VRM & RVT Training Program - Vehicle Familiarization
44The Open System Interconnection (OSI) model Internet and Intranet.The Open System Interconnection (OSI) modelA logical representation of the path data must travel in order to go through the network.Upper layers: Represent software that implements network services like encryption and connection management.Lower layers: Implement hardware-oriented functions like routing, addressing, and flow control.
45Internet and Intranet.The OSI modelData communication starts with the top layer of the stack at the sending side.Travels down the stack to the sender’s lowest (bottom) layer.Then traverses the physical network connection to the bottom layer on the receiving side, and up its OSI model stack.
46The OSI model – Data flow 13 April 2017Internet and Intranet.The OSI model – Data flowAn is sent from one user to another on the network.The passes through all seven layers on the sender’s computer (upper to lower) then go up all seven layers (lower to upper) on the receiving computer, until the is displayed on the screen of the addressed computer/user.VRM & RVT Training Program - Vehicle Familiarization
47Network Hardware and software Computer NetworksNetwork Hardware and software
48Network Hardware and Software. Aside from clients and servers, computer networks may also contain the following components:Network interface card (NIC).Hub.Bridge.Router.Modem.Gateway.Switch.Firewall.Operating System.
49Network Hardware and Software. Network interface card (NIC)Provides the physical interface between computer and cabling.In the computer, data moves along buses in parallel, as on a four-lane highway. But on a network cable, data travels in a single stream as on a one lane highway.The NIC’s job is to translate the data from the computer into signals that can flow easily along the cable. It does this by converting digital signals into analog signals.
50Network Hardware and Software. 13 April 2017Network Hardware and Software.Network interface card (NIC)Ethernet portNetwork port on the Toronto RocketCoaxial portVRM & RVT Training Program - Vehicle Familiarization
51Network Hardware and Software. HubHubs are devices used to link several computers together.A hub repeats any signal that comes in on one device and copies it to all other devices connected to the hub.There are two types of hubs:Passive hubs (not powered): connect all devices together.Active hubs (powered): use electronics to amplify and clean up the signal before it is broadcast to the other devices.
52Network Hardware and Software. 13 April 2017Network Hardware and Software.HubHUBVRM & RVT Training Program - Vehicle Familiarization
53Network Hardware and Software. BridgeJoins similar topologies and is used to divide LANs into segments.If a bridge knows the destination address, it is able to forward packets to that address, otherwise a bridge will forward the packets to all devices.Filters out noise.The main disadvantage of bridges is that they can’t connect dissimilar network types or perform intelligent path selection. For that function you require a router.
54Network Hardware and Software. Bridge: an exampleWith 200 clients on one Ethernet segment, the performance will be slower because of the design of the Ethernet and the number of workstations that are fighting to transmit information.By dividing the 200 clients into two segments of 100 clients each, the traffic will be much lower on either side, and speed will increase.
55Network Hardware and Software. RouterRouters are important devices that let messages flow between networks, rather than within networks.Home networks use a wireless or wired Internet Protocol router. An IP router, such as a digital subscriber line (DSL) or a cable modem broadband router, joins the home’s LAN to the WAN of the Internet.Broadband routers combine the functions of a router with those of a network switch and a firewall in a single unit.
56Network Hardware and Software. RouterWhen you connect to a website through an ISP and exchange information, there is no fixed connection between your computer and the Web server computer hosting the website. Routers find the best possible path, these paths avoid slow links and favour fast ones.
57Network Hardware and Software. 13 April 2017Network Hardware and Software.ModemStands for MODulator- DEModulator.Modern modems, such as cable TV and DSL modems, no longer modulate and demodulate the signals.Routers provide access to a LAN, however, in order for the router to connect to the Internet, it must be connected to a modem.The modern modem no longer works in the same way: converting digital to analog – electronic signals with audible freq (Modulating) and the converting that back to digital (Demodulating)However, the device that connects to the user to the Internet (WAN) is still referred to as a modem.VRM & RVT Training Program - Vehicle Familiarization
58Network Hardware and Software. 13 April 2017Network Hardware and Software.GatewayGateways are routers that rout between networks, however, they also perform protocol conversions so that different networks can work together.A gateway is an essential feature of most routers. A gateway may contain devices such as protocol translator, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability.VRM & RVT Training Program - Vehicle Familiarization
59Network Hardware and Software. 13 April 2017Network Hardware and Software.On the train: gateway exampleOn the TIN there is a Mobile Communications Gateway (MCG), which provides wireless communication between a train and the yard maintenance system.VRM & RVT Training Program - Vehicle Familiarization
61Network Hardware and Software. SwitchA switch is a computer network device that connects network segments.Network switches are capable of inspecting data packets as they are received, determining the source and destination device of that packet, and forwarding it appropriately.By delivering each message only to the connected device it was intended for, a network switch conserves network bandwidth allowing for better system performance.
62Network Hardware and Software. 13 April 2017Network Hardware and Software.SwitchComputers 1 and 5 transmit first and then 2 and 3.Simultaneous signals are sent by #1 and #5, and the switch directs them straight to their respective destination, without going through the rest of the connected devices.Same is repeated for #2 and #3.SWITCHVRM & RVT Training Program - Vehicle Familiarization
63Network Hardware and Software. Ethernet protocolEthernet uses a protocol called CSMA/CD, this stands for:Carrier SenseMultiple Accesswith Collision DetectionCSMA/CD
64Network Hardware and Software. Ethernet protocolCarrier SenseWhen a device connected to an Ethernet network wants to send data, it first checks to make sure it has a carrier on which to send its data (usually copper cable connected to a hub).Multiple AccessAll machines on the network are free to use the network.Collision DetectionEnsures that if two computers transmit data simultaneously, data re-transmissions are generated at differing time intervals.
65Network Hardware and Software. EthernetThe basic bus topology:The computers are daisy chained together.Each packet of data contains the destination address, the sender’s address and the data.
66Network Hardware and Software. 13 April 2017Network Hardware and Software.EthernetComputer 2 wants to send a message to computer 4.Computer 2 checks to make sure the network is not in use. If all clear, it will transmit the data onto the network.Signal is sent to every computer on the network but only addressed to computer 4, the other computers ignore it.Computer 4 sends a message back to computer 2 acknowledging receipt of data.VRM & RVT Training Program - Vehicle Familiarization
67Network Hardware and Software. 13 April 2017Network Hardware and Software.EthernetWhat happens if two computers try to transmit at the same time?A COLLISION occurs and each computer has to back off for a random period of time before retrying.On small networks, this goes unnoticed. On larger networks, the more collisions you have, the slower the network functions.Computer 2 and 5 both try to transmit simultaneously causing a collision which destroys the signals. After a random period of time, they retransmit.VRM & RVT Training Program - Vehicle Familiarization
68Network Hardware and Software. 13 April 2017Network Hardware and Software.Hub vs. switchAn Ethernet hub changes the topology from a bus to a star network.Collisions are still possible, however, hubs have centralized wiring, and can automatically bypass any ports that are disconnected or have cabling faults.VRM & RVT Training Program - Vehicle Familiarization
69Network Hardware and Software. 13 April 2017Network Hardware and Software.Hub vs. switchSwitches are used to overcome the problem of collisions.With a switch, computers can transmit simultaneously.Switches read the destination address and switch the signal directly to the recipient without broadcasting to all the computers on the network.VRM & RVT Training Program - Vehicle Familiarization
70Network Hardware and Software. 13 April 2017Network Hardware and Software.Hub vs. switchA vital difference between a hub and a switch is that all the devices connected to a hub share the bandwidth among themselves, while a device connected to a switch has the full bandwidth to itself.Example: If 10 devices are communicating using a hub on a 10 Megabits per second (Mbps) network, then each device may only get a portion of the 10 Mbps if other devices on the hub want to communicate as well. With a switch, each device can communicate at the full 10 Mbps.VRM & RVT Training Program - Vehicle Familiarization
71Network Hardware and Software. FirewallFirewall is a software loaded onto a network that serves as a barrier to keep destructive forces away from a network of computers.Firewall can block information from entering a network or from getting out of a network, they can permit different users to perform different kinds of operations, according to the user’s permissions.Packets of data are analyzed against a set of standards called filters. Filters block certain designated IP addresses.
72Filtering signals before allowing them to access the network FIREWALL
74Identify the type of network Review.Identify the type of networkLocal area network LANWide area network WAN
75Name the network components Review.Name the network componentsServerClientResource
76Name the network components that control the data transmission 13 April 2017Review.Name the network components that control the data transmissionExplain again, that the hub only repeats the signal to all the devices, and it’s up to the devices themselves to identify and receive the signals that are addressed to them. Causes delay, but is not noticeable in smaller networks.The switch reads the packet’s address and directs it accordingly, making the system much more efficient and suitable for large networks.HubSwitchVRM & RVT Training Program - Vehicle Familiarization
77Which of the following network topologies require terminators? Review.Which of the following network topologies require terminators?BusStarMesh