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Wireless Networking

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  1. Wireless Networking Chapter 9

  2. Contents • Explain wireless networking hardware and software requirements and configure wireless networking hardware • Define wireless networking IEEE standards and FCC operation frequencies • Define wireless network operation modes, limits, and methods • Configure wireless networking security • Describe troubleshooting techniques for wireless networks

  3. Introduction

  4. Wireless Networking • Wireless networking uses radio waves instead of wires to connect devices • Wireless networking is dominated by two technologies • IEEE 802.11 wireless Ethernet standard • Wireless Fidelity (Wi-Fi) • Home Radio Frequency (HomeRF) • Bluetooth

  5. Wireless Networking Basics

  6. Hardware • Wireless Ethernet NICs and Bluetooth adapters serve the same purpose as hardware in wired networks • Many wireless PCI NICs are simply wireless PC Card NICs housed on a PCI card

  7. USB Wireless NICs • Have the benefit of being placeable – able to move them around to get the best signal • Like moving the rabbit ears on an old TV set

  8. Adapters • Used by not just PCs but also printers, handheld computers, and PDAs

  9. Access Points • If you’re connecting a small group of PCs together in a decentralized workgroup, then the wireless NICs are all you need • If you wish to expand your network or to connect it to a wired network, you’ll need a wireless access point

  10. Wireless Bridges • Wireless bridges connect two different wireless segments or a wireless segment to a wired network • Point-to-Point bridges can only communicate with a single other bridge • Point-to-Multipoint bridges can talk to more than one bridge at a time

  11. Bluetooth Hardware • Wireless Bluetooth hardware is included as built-in equipment in many PCs, laptops, PDAs, and cell phones • Most Bluetooth add-on devices are USB External USB Bluetooth adapter

  12. Software • Wireless adapters come with a driver and a configuration utility • Windows XP comes with drivers and configuration utilities for wireless • The utility that came with the card is better to use • Browser-based utilities are common

  13. Ad-hoc Mode • Ad-hoc mode • Also called peer-to-peer mode • Each node directly contacts other nodes • Used for small networks • Two or more wireless nodes talking in ad-hoc mode form an Independent Basic Service Set (IBSS)

  14. Infrastructure Mode • Infrastructure mode • Use one or more wireless access points to connect the nodes centrally • Provides centralized control • Used for larger networks • A single wireless access point servicing a give area is called a Basic Service Set (BSS) • Add more access points to form an Extended Basic Service Set (EBSS)

  15. Security • Wireless networking devices provide no security out of the box • Hackers may easily grab packets right out of the air and read them • To provide better security, wireless networks use one of these methods: • Service Set Identification (SSID) or network names • Media Access Control address filtering • Data encryption

  16. Service Set Identification • The Service Set Identification (SSID) is a 32-bit string in the header of each packet • Only wireless clients whose SSID matches can gain access to the network • Wireless access points come with a generic SSID that is widely publicized by the vendor • Linksys uses linksys • 3Com uses 101 • Netgear uses wireless or netgear

  17. MAC Filtering • MAC address filtering limits access based on the physical, hard-wired address of the wireless network adapter • Any data packet whose MAC address is not listed in the wireless access point’s table is rejected • Specified MAC addresses may be denied • MAC addresses may be spoofed by hackers • Each MAC address needs to be manually entered initially and kept up to date

  18. Encryption • Encrypted data packets are electronically scrambled (locked) with a private encryption key before being transmitted • The receiving device must possess the encryption key in order to unscramble (unlock) the packet • Encryption is enabled through Wireless Equivalency Privacy (WEP) or Wi-Fi Protected Access (WPA) or WPA2

  19. Wireless Equivalency Privacy • WEP uses a 64-bit encryption algorithm • Works only on layers 1 and 2 (Physical and Data Link) • Encryption key is static (same from session to session) and shared by all network nodes • No user authentication

  20. Wi-Fi Protected Access • WPA offers • Dynamic encryption key generation issued on a per-user, per-session basis • Encryption key integrity-checking feature • User authentication through Extensible Authentication Protocol (EAP) • Not available on all wireless devices

  21. Speed • Ranges from 2 Mbps to 54 Mbps • Speed decreases as distance increases • Speed is affected by interference from other networking devices and solid objects • Dead spots may be created by things like refrigerators, air conditioners, metal plumbing

  22. Range • Environmental factors greatly affect range • Theoretical maximum ranges are usually listed, while the effective range may be about half as far • To extend range: • Add more wireless access points • Install a signal booster to increase the WAP’s signal

  23. Broadcasting Frequencies • The Federal Communications Commission (FCC) set aside the Industrial, Scientific, and Medical (ISM) frequencies for wireless networking • 83.5 MHz of bandwidth in the 2.4 GHz frequency band • 125 MHz of bandwidth in the 5.8 GHz band • 300 MHz of bandwidth (Unlicensed National Information Infrastructure (U-NII)) split into: • 5.15 to 5.25 GHz frequency band • 5.25 to 5.35 GHz frequency band • 5.725 to 5.825 GHz frequency band

  24. Media Access Methods • Multiple devices may share a medium by first listening in on the network media to see if it is busy • Devices need to wait if it is busy for the length of a frame plus the Interframe Space (IFS) • If two devices transmit at the same time a collision occurs and data is corrupted • How are collisions dealt with?

  25. CSMA/CD • Carrier Sense Multiple Access /Collision Detection • When a collision occurs (is detected), the device will wait a random amount of time and then attempt to resend the data

  26. CSMA/CA • Carrier Sense Multiple Access / Collision Avoidance • Instead of reacting to collisions, steps are taken to avoid collisions using Distributed Coordination Function (DCF) • Point Coordination Function (PCF) is defined but not implemented yet • DCF requires receiving nodes to send an Acknowledgement (ACK) for every packet that tells other nodes to wait a certain amount of time before trying to access the media

  27. RTS/CTS • Request To Send/Clear To Send (RTS/CTS) • Transmitting nodes send an RTS frame to the receiving node before transmitting any data • The receiving node responds with a CTS • Another form of collision avoidance

  28. Wireless Networking Standards

  29. 802.11 Standard • IEEE 802.11 wireless Ethernet standard defines methods to communicate using spread-spectrum radio waves • Broadcast data in small discrete chunks within a frequency range • All 802.11 wireless technologies use the 2.4 GHz frequency • Except for 802.11a that uses the 5 GHz frequency

  30. Direct-sequence spread-spectrum (DSSS) Sends data out on difference frequencies at the same time Uses 22 MHz bandwidth Greater throughput More prone to interference Used by most 802.11-based wireless networking standards Frequency-hopping spread-spectrum (FHSS) Sends data on one frequency at a time Constantly shifts or hops frequencies Uses 1 MHz bandwidth Used by HomeRF wireless networks Broadcasting Methods

  31. Wi-Fi Standards • Most widely adapted wireless networking technology today • Devices that conform to the extended versions of the 802.11 standard (802.11a, 802.11b, and 802.11g) are Wi-Fi certified • By the Wi-Fi Alliance (formerly the Wireless Ethernet Compatibility Alliance – WECA) • Wireless devices must use the same standard to communicate • 802.11g is backwards compatible with 802.11b

  32. 802.11 • The original standard • Slow speed at 2 Mbps • Limited range at about 150 feet • Uses the 2.4 GHz broadcast range • Security provided by WEP and WPA encryption • Rare today

  33. 802.11a • Operates in the 5 GHz frequency range with 8 available channels • Less crowded frequency range which reduces the chances of interference • Speeds up to 54 Mbps • Maximum range is around 150 feet • Developed after 802.11b • Not widely adopted

  34. 802.11b • Throughput up to 11 Mbps • Range up to 300 feet • Security through WEP and WPA encryption • Uses the 2.4 GHz frequency range with 14 available channels (11 in the U.S.) • Most widely used today which makes it more likely to suffer from interference

  35. 802.11g • Throughput up to 54 Mbps • Range up to 300 feet • Backwardly compatible with 802.11b • Newest version • Operates in 2.4 GHz range with 14 available channels (11 in the U.S.)

  36. 802.11 Standards

  37. 802.11 Standards

  38. 802.11 Standards • Security methods used by all: • SSID • MAC filtering • Industry standards WEP, WPA • Spread-spectrum method used by all: • DSSS • Communication modes supported by all: • Ad-hoc • Infrastructure

  39. HomeRF • Intended for home usage • Maximum range of 150 feet • Maximum speed of 2 Mbps • Version 2 maximum speed of 10 Mbps • Uses FHSS spread-spectrum broadcasting method – making it less susceptible to interference • Uses a Network ID (NWID) • 56-bit encryption algorithm • 7 channels in the 2.4 GHz range (6 for voice, 1 for data)

  40. Bluetooth • Bluetooth creates small wireless networks called Personal Area Networks (PANs) between PCs and peripheral devices • PDAs, printers, keyboards, mice, cell phones, home stereos, televisions, home security systems • Basis for upcoming IEEE 802.15 standard • Throughput from 723 Kbps to 1 Mbps • Maximum range of 10 meters (33 feet)

  41. Bluetooth Operation Modes • Operates in an automatic master/slave relationship • One master controls up to seven slave devices • A Bluetooth PAN is called a piconet (meaning very small) • Up to 255 devices may participate but only seven may be active at a time • An inactive slave device is called a parked device

  42. Bluetooth Communication Stages • Device discovery • Broadcasts its MAC address an a code identifying the type of device • May set device to non-discovery mode to skip this stage • Name discovery • Device identifies itself by a friendly name • Such as iPAQ Pocket PC • Association • Device officially joins the network • Some devices require a PIN code for security • Also called bonding, pairing, or joining • Service profile • Defines the kind of service it provides

  43. My Bluetooth Places

  44. Synchronous Connection-Oriented (SCO) Guarantees all data transmitted is received Good for file transfers Master nodes support up to 3 SCO connections at a time with up to 3 slave units Asynchronous Connectionless (ACL) No guarantee of delivery Faster Good for streaming media Point-to-point (master to slave) or broadcast (master to all slaves) links Data Transfer

  45. Bluetooth Services • Services supported by Bluetooth are called profiles • Generic Access Profile defines how units discover and establish connections • Service Discovery Profile enables discovery of services other devices provide • Cordless Telephony Profile defines wireless phone functionality • Intercom Profile defines wireless intercom functionality • Serial Port Profile enables a device to emulate serial port communication • Headset Profile defines wireless telephone and PC headset functionality

  46. Bluetooth Services • Dial-up Networking Profile defines capability to act as or interact with a modem • Fax Profile defines capability to act as or interact with a fax device • LAN Access Profile defines how a device accesses a LAN or the Internet • Generic Object Exchange Profile defines how to exchange data with other devices • Object Push Profile is used to exchange small data objects • File Transfer Profile is used to exchange large data objects like files • Synchronization Traffic is used to synchronize data between PDAs and PCs

  47. Bluetooth Services

  48. Bluetooth Security • 128-bit encryption and per-user passwords • Point-to-Point Tunneling Protocol (PPTP) and Secure Sockets Layer (SSL) for browser-based remote access • MAC filtering • Non-discovery mode to hide them from other devices

  49. Configuring Wireless Networking

  50. Wi-Fi and HomeRF • Install a wireless network adapter the same way as a wired adapter • Check Windows Device Manager after installation