Tonga Institute of Higher Education IT 141

1. Tonga Institute of Higher EducationIT 141 Lecture 6: LANS and WLANS

2. Network Classifications • Classified according to size and geographic scope -PAN (personal area network) – within a range of 30 feet (10 meters) - NAN (neighborhood area network) – within a limited geographical area, usually over several buildings - LAN (local area network) – connects personal computers within a very limited geographical area - MAN (metropolitan area network) – public high-speed network capable of voice and data transmission within a range of about 80 km - WAN (wide area network) – covers a large geographical area usually consists of several smaller networks We will focus on LAN because you are most likely to encounter this type of network.

3. LAN standards • It ranges from simple households to large businesses • LAN standards – LAN technologies are standardized by the Institute of Electrical and Electronic Engineers (IEEE). E.g. – IEEE 802.3 is sometimes used to refer to a network standard in articles and advertisements • Popular LAN standards – ARCnet, Token Ring, FDDI WERE POPULAR. • Today, most LANS configured with Ethernet technology and use compatible Wi-Fi standards in applications that require wireless access.

4. NETWORK DEVICES • node– A single device connected to a network • Workstation – personal computers connected to a network • Modem – uses phone lines to transmit data over a network • Network Interface Card (NIC) – network circuitry required to connect a computer to a LAN • Networked peripheral – any device that has network circuitry to directly connect to a network • Network attached storage (NAS)- storage device that directly connects to a network

6. CLIENTS, SERVERS, AND PEERS • Servers – a computer that provides services for other computers on a network called clients E.g. • Application server – run application software for network workstations • File server – stores files and supplies them to workstations on request

8. CLIENTS, SERVERS, AND PEERS • Workgroup (Peer-to-Peer) • A workgroup is a group of computer connected by a LAN, but not sharing similar information, like usernames and passwords. • This is commonly used in networks with less than five computers where each user has their own computer • Domain (Client-Server) • A domain allows all computers to be a part of a group that shares usernames, passwords and various settings. • This allows a user to log into any computer on a network with the same password, as well as using the same settings

10. Interconnecting various networks • Bridge – device that connects two similar networks • Gateways – device or software code used to join two networks that use different topologies. Term for any device or software to join two networks, even if they use different protocols or address range.

11. NETWORK LINKS • “communications channel” or link: physical path or a frequency for signal transmissions • Data in a network with wired links travels from one device to another over CABLES (E.g. – Ethernet, HomePNA, HomePlug) • Networks without wires transport data through the air or wireless network technologies(E.g. – Wi-fi, Bluetooth)

12. BANDWIDTH • Bandwidth- how much data can be transmitted over a network link over a certain amount of time (transmission capacity of a communications channel) • E.g. Coaxial cable brings more than 100 channels of cable TV, and has a higher bandwidth than your home telephone line. • 56Kbps (dial-up), 10Mbps (cable TV), 100Mbps (computer lab) • Network is slow your "bandwidth" is small. If something has a lot of bandwidth it is called broadband (Ethernet networks, cable TV) • If it has little bandwidth, it is called narrowband(phone lines, infrared)

13. COMMUNICATIONS PROTOCOLS • Protocol – a set of rules for interacting and negotiating. • Communications protocol – set of rules for efficiently transmitting data from one network node to another • Handshaking – process where a protocol helps two network devices communicate • TCP/IP – best known communications protocol

14. COMMUNICATIONS PROTOCOLS • Protocols are responsible for the following aspects of network communications: • Dividing messages into packets • Attaching addresses to packets • Initiating transmission • Regulating the flow of data • Checking for transmission errors • Acknowledging receipt of transmitted data

15. DATA TRAVELLING OVER A NETWORK

16. COMMUNICATIONS PROTOCOLS • Digital signals are transmitted as bits using limited set of frequencies • Analog signals can assume any value within a specified range of frequencies. • Digital equipment is sensitive to only two frequencies that represents 1s and 0s. • If there are errors, protocols usually correct these

17. PACKETS • Most communication protocols will divide data into small pieces, called packets, when sending over a network link • Packets – parcel of data that is sent across a computer network • Each packet contains – address of its sender, destination address, a sequence number, some data. At destination, packets rearrange themselves into original message according to sequence numbers.

19. SENDING MESSAGES • Circuit switching – technology used by communications networks, such as the telephone system • Packet switching – technology, which divides a message into several packets that can be routed independently to their destination. Every packet has destination addresses that communication protocols use

20. ADDRESS • Every node on a network has at least one address so that other nodes know how to send data to it. • A node may have other addresses depending on the protocols it uses. • Two commonly used Addresses: • Physical Address (network address, MAC address) • Logical Address (IP address)

21. IP ADDRESSES • Assigned IP addresses are semi-permanent and stay the same every time you boot your computer. (Static IP addresses) • It can also be obtained through DHCP (Dynamic Host Configuration Protocol). This protocol was designed to distribute IP addresses automatically. The next time you boot, you will be assigned with a different IP address. (Dynamic IP addresses)

22. Packets reaching destination • Packets might not travel directly to their destination. When it reaches its destination, it is checked for errors one last time and then the packets are reassembled into their original configuration.

23. WIRED NETWORKS • Uses cables to connect devices. • Advantages – fast, secure, simple to configure. • Disadvantages – devices connected have limited mobility. Running cables can be a problem with some building codes. Drilling can also be a problem • Examples– Ethernet, HomePNA, HomePlug technologies • Home PNA – uses telephone wires and coaxial cables • Powerline network – uses premises electrical wiring to form the infrastructure for a LAN

24. ETHERNET • Ethernet – simultaneously broadcasts data packets to all network devices. A pack is accepted by the device to which it is addressed • Ethernet relies on CSMA/CD [Carrier Sense Multiple Access with Collision Detection]. • Takes care of network devices transmitting packets at the same time • It detects collision, deletes the colliding signals, resets network and prepares to retransmit data • How fast? Original carried data over a coaxial cable bus topology at 10 Mbps. Today, up to 40 or 100 Gbps • Ethernet is popular because it is easy to understand, available almost everywhere, allows flexibility in network, and compatible with Wi-Fi networks

25. ETHERNET EQUIPMENT • Two or more Ethernet-ready computers (look for an Ethernet port, and determine it’s speed. If the computer doesn’t have one, install an Ethernet adapter, or Ethernet card/NIC) • An Ethernet router (hub – device that links two or more nodes of a wired network. Switch – sends data only to the devices specified as the destination. Router – ship data from one network to another) • Surge strip or UPS • Network Cables for each computer • Internet access device such as cable modem or DSL modem and corresponding cables

26. NETWORK DEVICES • Network device/appliance – electronic device that broadcasts network data, boosts signals, or routes data to its destination • Hub/Switch– a device that connects nodes on a network together (hub slow, switch fast) • Router– connects two different networks together (like a local network and the internet) • Repeater – amplifies signals on a network so that they don’t lose data to noise

27. Types of Links/Cables Twisted Pair cable – 4 copper wires twisted around each other. These are what are used for phone lines and Ethernet cables. They will end in a RJ-45 plug for Ethernet, or RJ-11 for a phone line Coax Cable – one wire that is surrounded by insulators to reduce data loss. Used for cable television and modems sometimes Fiber optic – A bundle of extremely small glass tubes. They do not use electric signals like the other cables, but use lasers instead. They are very fast and expensive

29. Wireless Networks/Cable-less • Does not use cables or wires • USES • 1. Radio – Uses what is called RF signals (radio waves). Sent and received with a transceiver (a transmitter and receiver combined) • 2. Microwaves – These can carry a lot of data, but need a direct line of sight to work well • Because radio and micro waves cannot bend to go around the curve of the earth, satellites are used in space to transmit signals around the globe • 3. Infrared light – uses light waves to transmit data. Only good for very short distances with clear line of sight

30. Wireless networks • Advantages • Mobility • No unsightly cables • Power spikes are much less likely to run through cables to damage workstations • Disadvantages • Was more expensive in the past • Speed • Range • Licensing • security

31. POPULAR TECHNOLOGY FOR WIRELESS NETWORKS • Wi-Fi • Bluetooth • Wireless USB (WUSB) • Wireless HD (WiHD)

32. Bluetooth • Short-range wireless network technology • Bluetooth networks automatically forms when two or more Bluetooth devices come within range of each other. • Piconet – a Bluetooth network • Operates at the unlicensed 2.4GHz frequency • Not for a collection of workstation but for mouse, keyboard or printer to computer connection • For PAN • Speed: Bluetooth 2.1 – 3 Mbps, range of 3 to 3000 feet. Bluetooth 3 – operates in the 6 to 9 GHz frequency range, peak speeds of 480 Mbps

33. Wi-Fi • Set of wireless networking technologies defined by IEEE 802.11 standards that are COMPATIBLE with Ethernet. • Transmits data as radio waves over 2.4 GHz or 5.8 GHz frequencies • Speed and range can be improved with various technologies including MIMO (multiple-input multiple-output)

34. Wi-Fi Standards

35. WIRELESS SETUP

36. WIRELESS SETUP • Check the computer’s if it has wireless capability • If not, you can add a Wi-Fi adapter and plug it into a PC slot or USB port • Wireless ad-hoc network: devices broadcasts directly to each other • Wireless infrastructure network: there a wireless access point (wireless router)

37. WIRELESS SETUP • Set up the router • Connec to the router with a computer • Configure router • Access the router setup utility • Create a new router password • Enter a SSID for the network • Activate WEP, WPA or PSK and create and encryption key • Set up the wireless workstations • Connect an Internet access device

38. Security through Encryption • LAN jacking – hackers interception signals driving through wireless enabled premises • Pinpoint wireless access point • Can see hackers in the list of clients accessing your network • Preventing interception is difficult, but encrypting makes data useless to intruders

39. WIRELESS ENCRYPTION • WEP (Wired Equivalent Privacy) • WPA (Wi-Fi Protected Access), WPA2 making sure that packets have not been intercepted . PSK (pre-shared key) a type of WPA, and PSK2 • To activate, use the router configuration utiliteis to select and encryption protocol, and create a wireless network key • Basis for scrambling and unscrambling. Key is similar to password.

40. ENCRYPTION • Transforms a message in such a way that its content are hidden from unauthorized readers • Can be used to • Scramble data over wired or wireless networks to prevent intrusions • Security credit card numbers and other personal information transferred from shoppers’ computers to e-commerce sites • Encrypting computer databases • Scrambling email contents to maintain privacy

41. How encryption works • Original message (plaintext/cleartext) Is encrypted to ciphertext. Converting ciphertext to plaintext is decryption. • Uses cryptographic algorithm and key • Cryptographic algorithm: way for encrypting or decrypting a message • Eg. Do not trust Brutus (see next slide) encrypted to GRQRWWUXVWEUXWXV

42. ENCRYPTION The algorithm for Caeser’s encryption technique was to offset letters of the alphabet.

43. Weak & Strong encryption • Weak encryption: Caeser’s simple substitution key • Strong encryption: very difficult to break • E.g. Advanced Encryption Standard (AES) used for WPA2 • Breaking encryption methods uses expensive, specialized, code-breaking computers • 32-bit key, 4.2 billion numbers, 40-bit key, 1 trillion numbers. • There is 56-bit and 64-bit • 128-bit and 256-bit takes a long time to decrypt • Most encryption uses 128-bit

44. Public key encryption • Symmetic key encryption: KEY used to encrypt a message is also used to decrypt • Public key encryption: uses one KEY to encrypt a message, but ANOTHER KEY to decrypt the message

45. Public Key encryption