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Training & Development Department Introduction to Computer Networks.

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1 Training & Development Department Introduction to Computer Networks

2 Training & Development Department 0714 Introduction to Computer Networks 2 Agenda Introduction. Types of Networks. Clients and Servers. Network Topologies. Internet and Intranet. Network Hardware and Software. Review.

3 Training & Development Department 0714 Introduction to Computer Networks 3 Purpose As 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.

4 Training & Development Department 0714 Introduction to Computer Networks 4 INTRODUCTION Computer Networks

5 Training & Development Department 0714 Introduction to Computer Networks 5 Introduction. Networks Two 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.

6 Training & Development Department 0714 Introduction to Computer Networks 6 Introduction. Resources Resources may be: Files. Folders. Printers. Memory. Applications.

7 Training & Development Department 0714 Introduction to Computer Networks 7 Introduction. Computer networking AdvantagesDisadvantages Communication between computer processing units (CPUs) Access restrictions Data sharingServer failures Hardware sharingPrivacy concerns Internet accessSecurity threats Data managementRedundancy

8 Training & Development Department 0714 Introduction to Computer Networks 8 TYPES OF NETWORKS Computer Networks

9 Training & Development Department 0714 Introduction to Computer Networks 9 Types of Networks. Network types Computer 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).

10 Training & Development Department 0714 Introduction to Computer Networks 10 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.

11 Training & Development Department 0714 Introduction to Computer Networks 11 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.

12 Training & Development Department 0714 Introduction to Computer Networks 12 WAN Types of Networks.

13 Training & Development Department 0714 Introduction to Computer Networks 13 CLIENTS AND SERVERS Computer Networks

14 Training & Development Department 0714 Introduction to Computer Networks 14 Clients and Servers. Servers A 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.

15 Training & Development Department 0714 Introduction to Computer Networks 15 Clients and Servers. IP addresses IP 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.

16 Training & Development Department 0714 Introduction to Computer Networks 16 Clients and Servers. Static IP addresses Located 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 Number HVAC position IP address

17 Training & Development Department 0714 Introduction to Computer Networks 17 Clients and Servers. Temporary IP addresses A 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.

18 Training & Development Department 0714 Introduction to Computer Networks 18 Clients and Servers. Client Clients 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.

19 Training & Development Department 0714 Introduction to Computer Networks 19 Clients and Servers. Client/server networking A 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.

20 Training & Development Department 0714 Introduction to Computer Networks 20 Clients and Servers. Client/server networking In 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.

21 Training & Development Department 0714 Introduction to Computer Networks 21 Clients and Servers. The relationship between a client and a server

22 Training & Development Department 0714 Introduction to Computer Networks 22 NETWORK TOPOLOGIES Computer Networks

23 Training & Development Department 0714 Introduction to Computer Networks 23 Network Topologies. Network topologies Network 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.

24 Training & Development Department 0714 Introduction to Computer Networks 24 Network Topologies. Network topologies Physical topology The physical structure of the network. The layout of the cables and connections between the network components. Logical topology Defined by the network protocols and explains how data travels across the cables.

25 Training & Development Department 0714 Introduction to Computer Networks 25 Network Topologies. Bus topology All 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.

26 Training & Development Department 0714 Introduction to Computer Networks 26 Information flow BUS TOPOLOGY

27 Training & Development Department 0714 Introduction to Computer Networks 27 Network Topologies. Ring topology All 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).

28 Training & Development Department 0714 Introduction to Computer Networks 28 Information flow RING TOPOLOGY

29 Training & Development Department 0714 Introduction to Computer Networks 29 Ring topology on the Toronto Rocket RING TOPOLOGY

30 Training & Development Department 0714 Introduction to Computer Networks 30 Network Topologies. On the train: ring switch Contains the network software. Assigns IP addresses. Enables communication over the TIN. Routes the signals to the TIMS for monitoring.

31 Training & Development Department 0714 Introduction to Computer Networks 31 Network Topologies. On the streetcar: ring switch Contains the network software. Assigns IP addresses. Enables communication over the streetcar network.

32 Training & Development Department 0714 Introduction to Computer Networks 32 Network Topologies. Star topology Devices 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.

33 Training & Development Department 0714 Introduction to Computer Networks 33 Information flow STAR TOPOLOGY

34 Training & Development Department 0714 Introduction to Computer Networks 34 Network Topologies. Mesh topology The 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.

35 Training & Development Department 0714 Introduction to Computer Networks 35 Information flow MESH TOPOLOGY

36 Training & Development Department 0714 Introduction to Computer Networks 36 Network Topologies. Hybrid topology A hybrid topology is produced when two, or more different basic network topologies are connected (bus, star, ring).

37 Training & Development Department 0714 Introduction to Computer Networks 37 INTERNET AND INTRANET Computer Networks

38 Training & Development Department 0714 Introduction to Computer Networks 38 Internet and Intranet. Internet vs. intranet Internet A 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 Protocol Internet Protocol TCP/IP

39 Training & Development Department 0714 Introduction to Computer Networks 39 Internet and Intranet. Internet protocol The 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.

40 Training & Development Department 0714 Introduction to Computer Networks 40 Internet and Intranet. Internet vs. intranet Intranet A 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. ‒

41 Training & Development Department 0714 Introduction to Computer Networks 41 Internet and Intranet. Network/communication protocols A 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.

42 Training & Development Department 0714 Introduction to Computer Networks 42 Internet and Intranet. Network/communication protocols Network 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.

43 Training & Development Department 0714 Introduction to Computer Networks 43 Internet and Intranet. Network protocols Network 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.

44 Training & Development Department 0714 Introduction to Computer Networks 44 Internet and Intranet. The Open System Interconnection (OSI) model A 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.

45 Training & Development Department 0714 Introduction to Computer Networks 45 Internet and Intranet. The OSI model Data 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.

46 Training & Development Department 0714 Introduction to Computer Networks 46 The OSI model – Data flow Internet and Intranet.

47 Training & Development Department 0714 Introduction to Computer Networks 47 NETWORK HARDWARE AND SOFTWARE Computer Networks

48 Training & Development Department 0714 Introduction to Computer Networks 48 Network Hardware and Software. Network 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.

49 Training & Development Department 0714 Introduction to Computer Networks 49 Network 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.

50 Training & Development Department 0714 Introduction to Computer Networks 50 Network interface card (NIC) Network Hardware and Software. Ethernet port Coaxial port Network port on the Toronto Rocket

51 Training & Development Department 0714 Introduction to Computer Networks 51 Network Hardware and Software. Hub Hubs 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.

52 Training & Development Department 0714 Introduction to Computer Networks 52 Network Hardware and Software. Hub HUB

53 Training & Development Department 0714 Introduction to Computer Networks 53 Network Hardware and Software. Bridge Joins 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.

54 Training & Development Department 0714 Introduction to Computer Networks 54 Network Hardware and Software. Bridge: an example With 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.

55 Training & Development Department 0714 Introduction to Computer Networks 55 Network Hardware and Software. Router Routers 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.

56 Training & Development Department 0714 Introduction to Computer Networks 56 Network Hardware and Software. Router When 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.

57 Training & Development Department 0714 Introduction to Computer Networks 57 Network Hardware and Software. Modem Stands 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.

58 Training & Development Department 0714 Introduction to Computer Networks 58 Network Hardware and Software. Gateway Gateways 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.

59 Training & Development Department 0714 Introduction to Computer Networks 59 Network Hardware and Software. On the train: gateway example On the TIN there is a Mobile Communications Gateway (MCG), which provides wireless communication between a train and the yard maintenance system.

60 Training & Development Department 0714 Introduction to Computer Networks 60 WLAN communication via the MCGs TIN DIAGRAM

61 Training & Development Department 0714 Introduction to Computer Networks 61 Network Hardware and Software. Switch A 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.

62 Training & Development Department 0714 Introduction to Computer Networks 62 Network Hardware and Software. Switch Computers 1 and 5 transmit first and then 2 and 3. SWITCH

63 Training & Development Department 0714 Introduction to Computer Networks 63 Network Hardware and Software. Ethernet protocol Ethernet uses a protocol called CSMA/CD, this stands for: Carrier Sense Multiple Access with Collision Detection CSMA/CD

64 Training & Development Department 0714 Introduction to Computer Networks 64 Network Hardware and Software. Ethernet protocol Carrier Sense When 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 Access All machines on the network are free to use the network. Collision Detection Ensures that if two computers transmit data simultaneously, data re-transmissions are generated at differing time intervals.

65 Training & Development Department 0714 Introduction to Computer Networks 65 Network Hardware and Software. Ethernet The basic bus topology: The computers are daisy chained together. Each packet of data contains the destination address, the sender’s address and the data.

66 Training & Development Department 0714 Introduction to Computer Networks 66 Ethernet Computer 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. Network Hardware and Software.

67 Training & Development Department 0714 Introduction to Computer Networks 67 Network Hardware and Software. Ethernet What 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.

68 Training & Development Department 0714 Introduction to Computer Networks 68 Network Hardware and Software. Hub Hub vs. switch An 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.

69 Training & Development Department 0714 Introduction to Computer Networks 69 Network Hardware and Software. switch Hub vs. switch Switches 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.

70 Training & Development Department 0714 Introduction to Computer Networks 70 Network Hardware and Software. switch Hub vs. switch A 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.

71 Training & Development Department 0714 Introduction to Computer Networks 71 Network Hardware and Software. Firewall Firewall 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.

72 Training & Development Department 0714 Introduction to Computer Networks 72 Filtering signals before allowing them to access the network FIREWALL

73 Training & Development Department 0714 Introduction to Computer Networks 73 REVIEW Computer Networks

74 Training & Development Department 0714 Introduction to Computer Networks 74 Local area network LAN Wide area network WAN Review. Identify the type of network

75 Training & Development Department 0714 Introduction to Computer Networks 75 Review. Name the network components ServerClientResource

76 Training & Development Department 0714 Introduction to Computer Networks 76 Review. Name the network components that control the data transmission HubSwitch

77 Training & Development Department 0714 Introduction to Computer Networks 77 Review. Which of the following network topologies require terminators? Star Bus Mesh

78 Training & Development Department 0714 Introduction to Computer Networks 78 ?

79 Training & Development Department 0714 Introduction to Computer Networks 79 End


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