Principles of computer Networking 18 March 2018

Principles of computer Networking 18 March 2018

Computer Network What is a network ? A network is a collection of computers and devices connected to each other. The network allows computers to communicate with each other and share resources and information 18 March 2018 2

Computer network When a network is needed ? When you want to share resources or exchange data or mutualize an internet connection Example of resources : - Printer - Hard Disk (external or internal) - Scanner - Internet connection - … 18 March 2018 3

Computer network What makes up a network? A network typically includes 4 things (besides the computers themselves): § Network interface cards (NICs): • cards that plugs into the back (or side) of your computers and lets them send and receive messages from other computers § Cable: • the medium to connect all of the computers together § Hub/Switch/Router: • hardware to perform traffic control § Protocol: • a set of communication rules to make sure that everyone speaks the same language 18 March 2018 4

Protocol : TCP/IP What does it mean ? TCP Transmission Control Protocol et IP Internet Protocol Computers are like humans beings in that they need to speak the same language in order to communicate. Each computer needs to be identified (with a unique "address") It can be compare to the Post Service. They need your name, your address, it must be an unique information to work. IP address will be your unique id (name, first name, …) The gateway will be the nearest Post Office DNS server (Domain Name Server) will be able to translate the "Internet name" (ex. : www. google. fr) into IP address (74. 125. 39. 104) 18 March 2018 5

Protocol : TCP/IP There is 2 ways to configure TCP/IP on computers. Static : You manage and enter manually the configuration Dynamic (DHCP : Dynamic host configuration protocol) : An automatic IP address will be given to your computer. This can be done either by a "server" or more currently by a router (ex. : Wi-Fi router) 18 March 2018 6

Protocol : TCP/IP Example of static TCP/IP configuration : Ip address : ex. : 172. 16. 2. 114 Subnet Mask : 255. 0 Default gateway : 172. 16. 2. 205 DNS Server 1 : 172. 16. 2. 212 DNS Server 2 : 172. 16. 2. 208 Warning : Only items on same IP class addresses can communicate. Ex. : 172. 16. 2. 114 (subnet mask 255. 0) will see 172. 16. 2. 2 Ex. : 172. 16. 2. 114 (subnet mask 255. 0) won't see 172. 16. 40. 2 18 March 2018 7

Computer Networking Advantages of Installing a Network § § Speed. Networks provide a very rapid method for sharing and transferring files. Without a network, files are shared by copying them to flash disks, then carrying or sending the disks from one computer to another. Cost. Because of sharing resources such as printer, scanner, . . . you don't have to buy many items. Resource Sharing resources is another area in which a network exceeds stand-alone computers. Most of missions cannot afford enough laser printers, modems, scanners, … for each computer. However, if these or similar peripherals are added to a network, they can be shared by many users. Flexible Access / Workgroup Computing. Mission networks allow users to access their files from every computers. Users can also work cooperatively through the network. Drawbacks of Installing a Network § § Expensive to Install. Although a network will generally save money over time, the initial costs of installation can be prohibitive. Cables, network cards and the installation may require the services of a technician. Requires Administrative Time. Proper maintenance of a network requires considerable time and expertise. File Server May Fail. Although a file server is no more susceptible to failure than any other computer, when the files server "goes down, " the entire network may come to a halt. Security. In case of "Workgroup" network, files are accessible to every body. RUser right access can only be implemented on Domain Network. But it requires to much knowledge and means. 18 March 2018 8

Cable Network Installing Cable - Some Guidelines When running cable, it is best to follow a few simple rules: § Always use more cable than you need. Leave plenty of slack. § Test every part of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolater. § Stay at least 1 meter away from fluorescent light boxes and other sources of electrical interference. § If it is necessary to run cable across the floor, cover the cable with cable protectors. § Label both ends of each cable. 18 March 2018 9

Wireless Network The term Wi-Fi often is used by the public as a synonym for wireless Internet (WLAN) A wireless access point (WAP) connects a group of wireless devices to an adjacent wired LAN Wireless adapters allow devices to connect to a wireless network A wireless router allows wired and wireless ethernet LAN devices to connect to a (usually) single WAN device such as cable modem or DSL modem Wired Equivalent Privacy (WEP) encryption was designed to protect against casual snooping, but is now considered completely broken. Wired Protected Access (WPA) which uses TKIP as a stopgap solution for legacy equipment. Though more secure than WEP, it has outlived its designed lifetime. WPA 2 encryption standards were released. If used with a 802. 1 X server or in pre-shared key mode with a strong and uncommon passphrase WPA 2 is still considered secure, as of 2009. 18 March 2018 10

Wireless Network Installing Wireless Network - Some Guidelines Follow a few simple rules: § Always protect your Wi-Fi access by a WPA encryption at least. Don't forget to protect the admin access. § Renew frequently the password. § Be aware that's the internet flow will be the same. It will be divided by the number of users. § Implement some wired connection in case of problem with the Wi-Fi 18 March 2018 11

Glossary § Local Area Network A Local Area Network (LAN) is a network that is confined to a relatively small area (capital, base, Paris HQ, …) § Wide Area Networks (WANs) connect larger geographic areas, such as Liberia, the Africa, or the world § Switch A switch is a device that provides a central connection point for cables from workstations, servers, and peripherals § Router A router translates information from one network to another § Wireless LANs Some networks are wireless. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. § Wi-Fi Wireless Fidelity synonym for wireless Internet (WLAN) § Ethernet could be labeled as the great grand-father of all the other network types § Internet The collection of computers, networks and their interconnections that are more or less publically accessible. § Intranet An intranet is a private computer network that uses Internet technologies to securely share any part of an organization's information or operational systems with its employees § Extranet An extranet can be viewed as part of a company's intranet that is extended to users outside the company (e. g. : normally over the Internet). § Fast Ethernet It's a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. § Gigabit Ethernet It's the next iteration, increasing the speed to 1000 Mbit/s 18 March 2018 12