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Chapter 5

Chapter 5. LANs and WLANs. Chapter Contents. Section A: Network Building Blocks Section B: Wired Networks Section C: Wireless Networks Section D: Using LANs Section E: Security Through Encryption. Network Building Blocks. Network Classifications LAN Standards Network Devices

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Chapter 5

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  1. Chapter 5 LANs and WLANs

  2. Chapter Contents • Section A: Network Building Blocks • Section B: Wired Networks • Section C: Wireless Networks • Section D: Using LANs • Section E: Security Through Encryption Chapter 5: LANs and WLANs

  3. Network Building Blocks • Network Classifications • LAN Standards • Network Devices • Clients, Servers, and Peers • Physical Topology • Network Links • Communications Protocols Chapter 5: LANs and WLANs

  4. Network Classifications • Personal Area Network (PAN) – interconnection of personal digital devices • Neighborhood Area Network (NAN) – connectivity spread over several buildings • Local Area Network (LAN) – usually connects computers in a single building • Metropolitan Area Network (MAN) – public high-speed network with range of about 50 miles • Wide Area Network (WAN) – consists of several smaller networks Chapter 5: LANs and WLANs

  5. LAN Standards • LAN technologies are standardized by the Institute of Electrical and Electronics Engineers (IEEE) Project 802 – Local Network Standards • IEEE 802.3 specifies the standards for Ethernet wired local area networks • How devices physically signal each other, how devices “share the wire in the wall”, etc. • Ethernet is the de facto standard for wired LAN in use today Chapter 5: LANs and WLANs

  6. Type 64 – 1518 bytes in length Ethernet Frame Structure IEEE 802.3 Ethernet frame • Preamble:8 bytes • 7 bytes with pattern 10101010, followed by one byte with pattern 10101011 (frame delimiter) • used to synchronize receiver, sender clock rates • Addresses:6 bytes, frame is received by all adapters on a LAN and dropped if address does not match • Type (Length):2 bytes, length of data segment (min. 46 bytes) • CRC (Cyclic Redundancy Check):4 bytes, created by sender, checked by receiver, if error detected, the frame is simply dropped Chapter 5: LANs and WLANs

  7. Network Devices • Each connection point on a network is referred to as a node • To connect to a LAN, a computer requires network circuitry, sometimes referred to as a network interface card (NIC) • A networked peripheral, or network-enabled peripheral, is any device that contains network circuitry to directly connect to a network • A network device, or network appliance, is any electronic device that broadcasts/re-broadcasts network data, boosts signals, or routes data to its destination Chapter 5: LANs and WLANs

  8. Network Devices Chapter 5: LANs and WLANs

  9. Clients, Servers, and Peers • Network devices can function as clients or as servers • Application server • File server • Print server • Networks that include one or more servers can operate in client/server mode Chapter 5: LANs and WLANs

  10. Physical Topology • The arrangement of devices in a network is referred to as its physical topology • Star: central connection point • Ring: attached to 2 neighbors • Bus: common, shared backbone • Mesh: multiple interconnections • Tree: stars on a bus • Two similar networks can be connected by a device called a bridge (or switch) • Gateway is a generic term for any device or software code used to join two networks Chapter 5: LANs and WLANs

  11. Network Links • A communications channel, or link, is a physical path or frequency for signal transmissions • Bandwidth is the transmission capacity of a communications channel (usually expressed in bits/sec, bps) • Broadband • Narrowband Chapter 5: LANs and WLANs

  12. Communications Protocols • Rules (Standards) for efficiently and effectively transmitting data from one network node to another. They define how to: • Divide messages into packets • Affix addresses (of the nodes) to packets • Initiate transmission (arbitrate access) • Regulate flow of data • Check for transmission errors • Acknowledge receipt of transmitted data (in some protocols) Chapter 5: LANs and WLANs

  13. Communications Protocols • A packet is a “parcel” of data that is sent across a computer network • Circuit-switching technology vs. • Packet switching technology • The Internet • Voice over IP (VoIP) • Advantages of one vs. the other? Chapter 5: LANs and WLANs

  14. Communications Protocols • Every packet that travels over a packet-switched network includes the address of its destination device • Most physical devices have more than one address • A MAC address is a unique number assigned to a network interface card when it is manufactured • An IP address is a series of numbers used to identify a network device in an internet • IP addresses can be assigned by registration, or obtained dynamically through DHCP Chapter 5: LANs and WLANs

  15. Wired Networks • Wired Network Basics • HomePNA and Powerline Networks • Ethernet • Ethernet Equipment • Ethernet Setup Chapter 5: LANs and WLANs

  16. Wired Network Basics • A wired network uses cables to connect network devices • Wired networks are fast, secure, and simple to configure and well-proven • Devices tethered to cables have limited mobility Chapter 5: LANs and WLANs

  17. HomePNA and Powerline Networks • HomePNA (HPNA) networks utilize existing telephone wiring to connect network devices • Special NICs and cables are required • Powerline networks transmit data over power lines as low-frequency radio waves Chapter 5: LANs and WLANs

  18. Ethernet • Simultaneously broadcasts data packets to all network devices (a star topology) • IEEE 802.3 defines the Ethernet protocol • CSMA/CD protocol used to share the channel • Vary in speed from 10Mbps to 10Gbps Chapter 5: LANs and WLANs

  19. Ethernet On an Ethernet, data travels on a first come, first served basis. If two workstations attempt to send data at the same time, a collision occurs. That data must be resent. Chapter 5: LANs and WLANs

  20. Ethernet Equipment Checking a workstation for an Ethernet port Chapter 5: LANs and WLANs

  21. Ethernet Equipment • Ethernet adapter - NIC (designed to support the Ethernet protocols) • Network hub • Network switch • Network router • RJ45 connector Chapter 5: LANs and WLANs

  22. Typical Ethernet Setup Technically, this device functions as an Ethernet switch, as well as an IP router. Chapter 5: LANs and WLANs

  23. Wireless Networks • Wireless Basics • Bluetooth • Wi-Fi • Wi-Fi Equipment • Wi-Fi Setup Chapter 5: LANs and WLANs

  24. Wireless Basics • A wireless network transports data from one device to another without cables or wires • RF signals • Transceiver • Microwaves • Infrared light • Slower than wired networks • Security concerns Chapter 5: LANs and WLANs

  25. Bluetooth • Bluetooth is a short-range, wireless network technology designed to make its own connections between electronic devices, without wires, cables or any direct action from a user (a piconet) Chapter 5: LANs and WLANs

  26. Wi-Fi • Wireless networking technologies that are compatible with Ethernet (per IEEE 802.11) • MIMO technology uses two or more antennae to send multiple sets of signals Chapter 5: LANs and WLANs

  27. Wi-Fi Equipment Chapter 5: LANs and WLANs

  28. Wi-Fi Equipment • If your computer is not pre-equipped with wireless circuitry, you can purchase and install a Wi-Fi card Chapter 5: LANs and WLANs

  29. Wi-Fi Equipment • Wireless network setups • Wireless ad-hoc network • Wireless infrastructure network • Wireless access point • Wireless router Chapter 5: LANs and WLANs

  30. Wi-Fi Setup • Set up the router • Connect to the router with a computer • Configure the router • Access the router setup utility • Create a new router password Chapter 5: LANs and WLANs

  31. Wi-Fi Setup • Enter an SSID for the network • Activate WEP, WPA, or WPA2 and create an encryption key(!!) • Set up the wireless workstations • Connect an Internet access device • Generally a modem that will connect to the service available in your area (cable, DSL, etc.) from your service provider (ISP) Chapter 5: LANs and WLANs

  32. Typical Wi-Fi Setup Chapter 5: LANs and WLANs

  33. Using LANs • LAN Advantages and Challenges • Sharing Files • Sharing Printers • LAN Parties • Troubleshooting Chapter 5: LANs and WLANs

  34. LAN Advantages • LANs enable people to work together • Sharing networked software can reduce costs • Sharing data on a LAN can increase productivity • Sharing networked hardware can reduce costs • Sharing networked hardware can provide access to a wide range of services and specialized peripheral devices (read “expensive”) Chapter 5: LANs and WLANs

  35. LAN Challenges • Resources become unavailable when network malfunctions • Networks may be vulnerable to unauthorized access • More vulnerable than standalone computers • Wireless networks can be tapped from a “snooping” computer • Networked computers are susceptible to an increasing number of worms, Trojan horses, and blended threats Chapter 5: LANs and WLANs

  36. Sharing Files • If you use Windows, it automatically detects available LANs any time you turn on a workstation • To connect to a shared resource, you might be asked for a user ID and password Chapter 5: LANs and WLANs

  37. Sharing Files In this drive mapping example, a server’s drive C is mapped as drive F by a workstation. After the mapping is complete, the server’s hard disk appears in the workstation’s directory as drive F and can be used just as though it were a drive connected directly to the workstation. Chapter 5: LANs and WLANs

  38. Sharing Files To allow other network users to access files or folders on your Windows computer, you have to designate them as shared (commonly, via Windows Explorer) Chapter 5: LANs and WLANs

  39. Sharing Printers • Three setups allow for printer sharing: • Set up printer sharing using a workstation printer • Set up printer sharing using a print server • Install printer with built-in networking Chapter 5: LANs and WLANs

  40. Sharing Printers • In Windows, use the Printers and Faxes dialog box to allow other users to share the printer attached to your workstation Chapter 5: LANs and WLANs

  41. Security Through Encryption • Wi-Fi Security • Encryption Chapter 5: LANs and WLANs

  42. Wi-Fi Security • Wireless networks are much more susceptible to unauthorized access and use by casual users than wired networks • LAN jacking, or war driving, is the practice of intercepting wireless signals by cruising through an area Chapter 5: LANs and WLANs

  43. Wi-Fi Security • Wireless encryption scrambles data transmitted between wireless devices and then unscrambles the data only on devices that have a valid encryption key • WEP (Wired Equivalent Privacy) • WPA (Wi-Fi Protected Access) • WPA2 • Activate encryption by using a wireless network key Chapter 5: LANs and WLANs

  44. Encryption • Encryption transforms a message so that its contents are hidden (encrypted) from unauthorized readers • Plaintext has not yet been encrypted • An encrypted message is referred to as ciphertext • Decryption is the opposite of encryption • Cryptographic algorithm • Cryptographic key Chapter 5: LANs and WLANs

  45. Encryption • Weak vs. strong encryption • AES (Advanced Encryption Standard) • Encryption methods can be broken by the use of expensive, specialized, code-breaking computers • Brute-force method Chapter 5: LANs and WLANs

  46. Encryption • Public key encryption (PKE) eliminates key-distribution problem, by using one key to encrypt a message and another key to decrypt the message Chapter 5: LANs and WLANs

  47. Chapter 5 Complete LANs and WLANs

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