Networking

1. Networking IGCSE ICT Mrs. Ghazaal

2. Networking Every time we connect to the internet from our PC, laptop, tablet, or smartphone, we are accessing data held on another computer somewhere else in the world Computer networks enable computers to communicate with each other and share data and information We will look at the hardware needed to enable communication and the transfer of data

3. Hubs, Switches, bridges, routers Hubs, switches, bridges and routers are all devices that let you connect one or more computers to other computers, networked devices, or to other networks. Each has two or more connectors called ports into which you plug in the cables to make the connection.

4. HUBS • 8 to 16 ports • Does not read any of the data • Data packets sent to all the devices connected to it (including back to the device that sent the signal in the first place) • Only the device for which it was intended will accept the data packets • Passive hub simply sends the signal, whereas an Active hub amplifies it (makes the signal stronger) • Least Expensive, least intelligent, least complicated. • Quick and easy way to connect computers in a small network • Broadcasts data packets to computers in a LAN

5. SWITCHES • Essentially does what a hub does but more efficiently. • Able to look at a data packet, target the computer for which it is intended, and send it only to whom it was intended to be sent, not to everyone on the network. • On busy networks this can make the • network significantly faster. • Directs data packets to specific computers

6. BRIDGES • Allows 2 dissimilar network topologies to send messages from one to the other. • Connects 2 LANs • Most modern networks prefer to use routers, not bridges because data being sent across a bridge must be in the same format • Directs data packets to specific networks

7. ROUTERS • Behaves like a bridge, provides a link between 2 or more networks, but is more ‘intelligent’ • can be programmed to understand, possibly manipulate, and decide the best route for the data to take • . Routers are located at gateways(the places where two or more networks connect). • Because routers can join very different networks together, their main use is to provide connections between networks and the internet.

8. NETWORK SERVERS • A network server is a computer that provides various shared resources to workstations and other servers on a computer network • What separates a server from a workstation is not the hardware, but rather the function performed by the computer. • In general, a workstation is any computer used by an individual person to perform his or her job duties, while a network server is any computer that provides users with access to shared software or hardware resources. • The shared resources can include disk space, hardware access, and email services

9. Examples of Servers • File server - users store files on the network file server. Users can do all the usual file functions - copy, delete, change, duplicate by sending commands to the file server. • Print server - on larger networks there is often a computer whose sole task is to manage printing jobs sent to a networked printer. This machine is called the print server. Printing in this way frees up the user computer to do other things. • A web server is a computer that stores websites on the Internet and delivers web pages to viewers upon request. This service is referred to as web hosting.

10. INTERNET INTERNET Many connections to the internet Can incorporate a firewall Router Router Proxy Server Connections from the users ‘piggy back’ on a single connection to the Internet Proxy server has to remember who sent which message to the ISP, when responses are sent back, it must make sure that they are directed to the correct computer. (special proxy server = firewall)

11. Proxy Server • Proxy Server has many other functions – including relieving network traffic so the server is less taxed • A company that provides Internet connectivity to its employees might configure a proxy server to block requests for certain websites • Can act as a web server • Can act as a buffer (between internet and LAN) • Server passes on requests to the internet • Passes the requested web pages to individual computers • Stores web pages for faster re-use by computers • Can be used to monitor internet usage

12. Network Interface Card(NIC) • Printed circuit board that plugs into one of the slots on the motherboard. • Every computer attached to a network needs a NIC, it enables the computer to link to the cable or radio waves used to communicate across the network. • Allocated the IP address • Usually fitted with a connection point for a hardwired network, although most now allow wireless connection. • If your computer already has Wi-Fi, it will have a wireless NIC built in

13. Dedicated Cabling • Communication Medium allows signals to be transmitted around the network = cables and radio waves • Twisted Pair - consists of a pair of braided copper cables. They are braided to help protect them from electromagnetic interference and hence data loss in such a system. Limited distance between network points. • Fibre Optic – carry data as light signals. Light signals are not affected by interference. Most expensive type of cabling, also the fastest, and can send data across vast distances (world’s continents are all interconnected with undersea fibre-optic cables)

14. Wireless technology Wireless technology allows devices to be connected to a network without physical wires, instead using radio transmitters and receivers. • Bluetooth Technology – limited to a short range of metres and generally used to link and transfer data between mobile devices, smartphones, and computer peripherals like a wireless keyboard, mouse and printer, also used for video game consoles • Wi-Fi technology has a much wider range, able to transfer large amounts of information and used with larger computer networks and devices.

15. Local Area Network (LAN) • A network spread over a small area consisting of computers and peripheral devices, such as printers. • Each computer in a LAN can work as a stand-alone computer, with its own software • Computers can also use software stored on the network server (runs the network operating system and manages resources over the network)

16. Router used to connect LAN’s together and to connect them to the Internet (if needed) Router will inspect every packet of data being sent by any computer on the networks connected to it. Router Router is usually connected to one port on one switch on each LAN. Switch Finance Department LAN Switch • Router sends packet to switch • If address does not match any device on the network, it will pass it on to another switch Marketing Department LAN Switch Human Resources Department LAN

17. Advantages and disadvantages of LAN’s compared with stand-alone computers

18. WLAN & WNIC • Wireless LAN • No wires or cables (only wiring that connects the WLAN access points together) • Uses radio waves or infrared signals • Devices can communicate over a limited area within range of the nearest wireless access point • Devices can be added easily with no cabling • Drawbacks-could be security issues, interference problems, generally slower than cable based LAN’s • Routers are not essential for a WLAN, they are only needed if you want to connect a WLAN to the internet • Wireless NIC • Works the same way as a NIC, but uses radio waves • In order to use a laptop in a WLAN, it needs a WNIC

19. Wireless Router • Looks like a regular router with an antenna. • Wired connection to the internet broadband connection • Basically speaking, internet data comes in to the router from the phone line (or DSL) and is converted into radio signals. This signal is then picked up by the network card in your computer or console and translated into internet data again. • Provide wireless internet to wireless-enabled devices such as computers, laptops, tablets and gaming consoles • Can be used to make VoIP calls • Some routers are 5 in 1: Modem, router, firewall, 4-port switch & wireless access point • WAP (Wireless Access Point) • Plugs into the network via a cable, is not a router as it cannot perform those functions; it is more like a hub • Businesses are more likely to have separate WAPs and routers because they use more powerful devices than individual users.

20. Cables or wireless?

21. WLANs

22. If the concentrator breaks down the whole network will crash ! All data communications go through this central hub/switch STAR NETWORK

23. BUS NETWORK File Server – normally used to store user data; allows users to save and load data using the network rather than saving on their machines Each device is connected to a common spine (spine = cabling with network leads attached to it and each computer). Each end of the spine has a terminator(absorb signals so that they don’t get reflected back into the network and cause data corruption). No hub or switch needed, and less cable so it’s less expensive than star. Problem with spine=network down. Not so common anymore.

24. HYBRID NETWORK Each hub (switch) and server are connected to a common bus-type backbone often no need for terminators, hubs(switches) perform that function, must be at least 2 Very popular with network managers right now Easy to connect new devices; one device failure will not affect network; each device can be inspected without disturbing the network Can be difficult to wire sections together; faults in the hubs/switches will cause that section to go down, fault in the spine will cause the whole network to go down. Quite often hubs will link to each other forming stars within stars

25. Users require computer hardware, browser software, local wiring infrastructure and an Internet Service Provider (ISP) to connect to the internet

27. BANDWIdTH • Measure that quantifies (makes it a measurable #) the capability of a communication channel to transmit information. • Digital = measured in bits per second • Generally the wider the bandwidth is the faster it is.

28. BROADBAND • Broadband can refer to high-speed Internet services, fiber optic services, cellular services or broadcasting services, to name a few. • Broadband Internet technologies have all but replaced dial-up service for delivering high-speed Internet connectivity to desktops and to portable devices, to individuals and to private and public networks. Among Internet providers you’ll find Digital Subscriber Line (DSL) services, cable services, fiber optic services, and cellular services. Of these, cellular broadband is the only wireless Wide Area Network (WWAN) Internet service, though a wireless modem can be used with any of the other services to create a wireless Local Area Network (WLAN), or hotspot. • Broadband services of all kinds have become central to modern living. From television to the cell phone, from local networking to national infrastructures, broadband network services carry the information we rely on for everything from cashing a check to flying safely on a plane. The only thing more amazing than our reliance on broadband is, perhaps, that it’s been around such a short time relative to its importance.

29. intranet • Think of an intranet as a company's own private information network • Website located on a private network within an organisation • Only members of the organisation can access the intranet and they are the only ones who can send information to it. • Can be made up a number of LAN’s and it is possible to gain access to a WAN such as the internet (Intranets can also be run completely independent of the internet) • Firewalls prevent outside people from gaining access to the intranet • Provide security by using firewalls, log-in access and secure servers. • Intranet • IP Addresses • URL to identify files or data • Has pages which look like Internet pages because they are created the same way. • Access to information is via a web browser, just like on the Internet • This is a major advantage over a traditional LAN because the intranet is independent of the type of workstation or software being used on the network. • Typical uses of an intranet would be: • Viewing internal web pages (e.g. company calendars, etc.) • Internal e-mail and instant-messaging between workers • Sharing of internal documents

30. Extranet: means of extending an organisations intranet for use by selected outside people. • One very valuable application for an extranet is customer service. Online patches, upgrades, downloads, knowledge bases, and an interactive Help Desk are just a few examples of ways to serve a client base using an extranet

34. Things to know about WANS • Internet: special type of WAN; network of computer networks. All computers on the internet are either clients or servers. • Clients – able to access the web and ask for information, which the web server provides • Servers – provide services

35. The Internet is an International Network of computers that allows users to use email, browse the World Wide Web or to chat either by text or by voice It is important that you know that the World Wide Web is a part of the internet. You access the web by using a web browser (software) like Mozilla Firefox, Google Chrome, etc.

36. Network / data security • As soon as your computer is connected to a network, you have to start thinking about security – security of your files, information, etc. A network allows a person who does to have physical access to your computer (they are not sitting in front of it) to gain access all the same. If your computer is connected to a network, other people can connect to your computer. A person who gains unauthorised access to a computer system is often called a hacker. Securing Your Data • Often we have data that is private or confidential. This data needs to be protected from being viewed by unauthorised people. This is especially true if the data is to be sent via a public network such as The Internet.The best way to protect data is to encrypt it.

37. Levels of Access Network managers can set up groups of users with different levels of access to the network. At the highest level, the network manager can install and remove software, access all user areas and change permissions. At lower levels, a group of users may only be able to access particular pieces of software and their files stored in their own areas. Different levels of access help to ensure that the network remains secure and that only licensed software is used on it. Your level of access is linked to your User ID

38. firewalls The way firewalls work is to filter out information from a message and see if it is allowable traffic. A firewall restricts access by identified computers by noting and blocking specific IP addresses or blocking certain types of internet traffic A firewall is a device, or a piece of software that is placed between your computer / LAN and the rest of the network / WAN (where the hackers are!) A firewall blocks unauthorised connections being made to your computer or LAN. Normal data is allowed through the firewall (e.g. e-mails or web pages) but all other data is blocked. If an organisation does not have a firewall in place then all their computers become accessible to unauthorised users via the Internet.

39. authentication Authentication techniques are used to identify users to a computer-based system or network Strong authentication is generally considered to be a multi-factored method of confirming the identity of a person seeking access to information or entry into a restricted area. The factors for verifying the identity of an individual are something the person knows, something the person has and something physically particular to that person The first of these identifying factors, something the person knows, is a presumably secret item of information. This might be a password or a personal identification number (PIN). The second factor, something the person has, is a unique item such as a bank card containing a data chip, passport or hardware token (a physical object, where the user's interaction with a login system proves that the user physically possesses the object). The third factor is a physically identifying characteristic such as a fingerprint or retinal scan. A common implementation of strong authentication using two of these factors is the use of a PIN number with a bankcard.

40. Biometric Devices • Biometrics means to measure and analyze human characteristics in order to correctly identify an individual • Examples of physical characteristics that can be used are: • Fingerprints • Voice Recognition • Retinas or irises • Facial patterns • Palm Prints • Special devices are needed to capture the biometric data which is then passed onto the computer for processing and identification.Biometric authentification methods can be used to identify you at ATMs to withdraw cash, in computer networks to allow you to log on and many schools are now introducing 'fingerprint registration'! • Believed to be more secure because the physical characteristics are unique to every individual and cannot be stolen, copied or lost. • Far from foolproof; many errors and false accepts are possible

41. encryption Encryption is the name given to the converting of data into code by scrambling or encoding it. Encryption involves taking a piece of data and translating it into a coded version of itself (ciphertext). The resulting symbols appear all jumbled up If a hacker gains access to the data they will not be able to understand it. The computer that is sending the message uses an encryption key to encode the data, the receiving computer has a decryption key that can translate it. Encryption is the process of converting information into a form that is meaningless to anyone except holders of a ‘key’

42. The encryption scheme shown here is called Symmetric Key, or Single Key encryption. There are many better schemes, such as Public Key Encryption, but the one shown here is the easiest to understand! First Alice needs to generate a secret ‘key’.The key is usually a very long, random number. Alice must then give a copy of this key to Bob. She must make sure that nobody else can get to the key (So maybe Alice will visit Bob and give him a copy of the key on a memory stick or floppy disc). Now that Bob has a copy of the key, each time Alice needs to send him a message she starts by encrypting it using special encryption software and the secret key. The encrypted message now looks like a jumble of random letters and numbers. Alice then sends the encrypted message to Bob. She can use a public network like the Internet, since, even if it gets stolen, the encrypted message cannot be read or understood without the key. When Bob receives the message, he uses special decryption software and his copy of the secret key to decrypt the message. Bob can now read the original message from Alice.