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CWNA Guide to Wireless LANs, Second Edition

CWNA Guide to Wireless LANs, Second Edition

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CWNA Guide to Wireless LANs, Second Edition

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  1. CWNA Guide to Wireless LANs, Second Edition Chapter Two Wireless LAN Devices and Standards

  2. Objectives • List WLAN devices and describe their basic functions • Explain the different types of communication standards and why standards are important • List the three major wireless standards and regulatory agencies and their functions • Describe the different IEEE WLAN standards CWNA Guide to Wireless LANs, Second Edition

  3. WLAN Devices: Wireless Network Interface Card • Network interface card (NIC): Connects computer to network so that it can send and receive data • Wireless NICs perform same function, but without wires • When wireless NICs transmit: • Change computer’s internal data from parallel to serial transmission • Divide data into packets and attach sending and receiving computer’s address • Determine when to send packet • Transmit packet CWNA Guide to Wireless LANs, Second Edition

  4. WLAN Devices: Wireless Network Interface Card (continued) Figure 2-1: Network interface card for a wired network CWNA Guide to Wireless LANs, Second Edition

  5. WLAN Devices: Wireless Network Interface Card (continued) Figure 2-2: Wireless NICs for desktop computers: (a) PCI network interface card, (b) standalone USB device, (c) USB key fob CWNA Guide to Wireless LANs, Second Edition

  6. WLAN Devices: Wireless Network Interface Card (continued) Figure 2-3: Wireless NICs for laptop computers: (a) CardBus card; (b) Mini PCI card CWNA Guide to Wireless LANs, Second Edition

  7. WLAN Devices: Wireless Network Interface Card (continued) • For smaller devices, several options: • CardBus or Type II PC Card • May require a sled • CompactFlash (CF) card: Consists of small circuit board containing flash memory chips and dedicated controller chip • Small and consume little power • SDIO (Secure Digital I/O) or SDIO NOW! Card: Provides high-speed data input/output with low power consumption CWNA Guide to Wireless LANs, Second Edition

  8. WLAN Devices: Wireless Network Interface Card (continued) • A movement towards integrating wireless NICs • Would eliminate need for external wireless NICs • Software drivers necessary to allow wireless NIC and operating system (OS) to interface • Windows XP and PDA OSs have built-in drivers CWNA Guide to Wireless LANs, Second Edition

  9. WLAN Devices: Access Point • Three major parts: • Antenna and radio transmitter/receiver • RJ-45 wired network interface • Special bridging software • To interface wireless devices to other devices • Two basic function: • Base station for wireless network • Bridge between wireless and wired networks CWNA Guide to Wireless LANs, Second Edition

  10. WLAN Devices: Access Point (continued) Figure 2-6: An access point acts as a bridge between the wireless network and a wired network CWNA Guide to Wireless LANs, Second Edition

  11. WLAN Devices: Access Point (continued) • Range depends on several factors: • Type of wireless network supported • Walls, doors, and other solid objects • Number of wireless clients that single AP can support varies: • Theoretically over 100 clients • No more than 50 for light network use • No more than 20 for heavy network use • Power over Ethernet (PoE): Power delivered to AP through unused wires in standard unshielded twisted pair (UTP) Ethernet cable CWNA Guide to Wireless LANs, Second Edition

  12. WLAN Devices: Remote Wireless Bridge • Bridge: Connects two network segments together • Even if they use different types of physical media • Remote wireless bridge: Connects two or more wired or wireless networks together • Transmit at higher power than WLAN APs • Use directional antennas to focus transmission in single direction • Delay spread: Minimize spread of signal so that it can reach farther distances • Have software enabling selection of clearest transmission channel and avoidance of noise and interference CWNA Guide to Wireless LANs, Second Edition

  13. WLAN Devices: Remote Wireless Bridge (continued) Figure 2-8: Point-to-point remote wireless bridge CWNA Guide to Wireless LANs, Second Edition

  14. WLAN Devices: Remote Wireless Bridge (continued) Figure 2-9: Point-to-multipoint remote wireless bridge CWNA Guide to Wireless LANs, Second Edition

  15. WLAN Devices: Remote Wireless Bridge (continued) • Four modes: • Access point mode: Functions as standard AP • Root mode: Root bridge can only communicate with other bridges not in root mode • Non-root mode: Can only transmit to another bridge in root mode • Repeater mode: Extend distance between LAN segments • Placed between two other bridges • Distance between buildings using remote wireless bridges can be up to 18 miles at 11 Mbps or 25 miles transmitting 2 Mbps CWNA Guide to Wireless LANs, Second Edition

  16. WLAN Devices: Remote Wireless Bridge (continued) Figure 2-10: Root and non-root modes CWNA Guide to Wireless LANs, Second Edition

  17. WLAN Devices: Remote Wireless Bridge (continued) Figure 2-11: Repeater mode CWNA Guide to Wireless LANs, Second Edition

  18. WLAN Devices: Wireless Gateway • Combines wireless management and security in single appliance • Authentication • Encryption • Intrusion detection and malicious program protection • Bandwidth management • Centralized network management CWNA Guide to Wireless LANs, Second Edition

  19. Understanding Standards • Standards make it easier to purchase and use wide variety of products • Wireless technology based on standards • Standards help ensure different products from different vendors function in same capacity CWNA Guide to Wireless LANs, Second Edition

  20. The Need for Standards • Standards for telecommunications have been essential since very beginning • Without standards telecommunications would essentially be impossible • Some IT professionals believe that standards have stifled growth in the field • Waiting for standards to catch up to changes slows down process of change and development • In reality, standards have proven to be more beneficial than harmful CWNA Guide to Wireless LANs, Second Edition

  21. Advantages and Disadvantages of Standards Table 2-1: Advantages and disadvantages of standards CWNA Guide to Wireless LANs, Second Edition

  22. Types of Standards • De facto standards: Common practicesthat the industry follows for various reasons • Ranging from ease of use to tradition to what majority of users do • Usually established by success in marketplace • De jure standards: Official standards • Controlled by organization or body that has been entrusted with that task • Process for creating these standards can be very involved CWNA Guide to Wireless LANs, Second Edition

  23. Types of Standards (continued) • One complaint against de jure standards is amount of time it takes for a standard to be completed • Consortia: Usually industry-sponsored organizations that want to promote a specific technology • Goal is to develop a standard that promotes organization’s specific technology in little time CWNA Guide to Wireless LANs, Second Edition

  24. Enforcing Standards • Marketplace itself enforces some standards • Standards created by consortia often regulated by marketplace • De jure standards often enforced by outside regulatory agency • Ensure that participants adhere to prescribed standards • Must have power to enforce standards and effectively punish those who refuse to abide by them CWNA Guide to Wireless LANs, Second Edition

  25. Wireless Standards Organizations and Regulatory Agencies • Three primary standard-setting and regulatory bodies that play major role in wireless LAN technology • Institute of Electrical and Electronics Engineers (IEEE) • Wi-Fi Alliance • U.S. Federal Communications Commission (FCC) CWNA Guide to Wireless LANs, Second Edition

  26. Institute of Electrical and Electronics Engineers (IEEE) • Establishes standards for telecommunications • Also covers wide range of IT standards • World’s largest technical professional society • 37 Societies and Councils • Publish technically focused journals, magazines, and proceedings • Work on over 800 standards • Best known for its work in establishing standards for computer networks • Project 802 CWNA Guide to Wireless LANs, Second Edition

  27. Institute of Electrical and Electronics Engineers (continued) Table 2-2: Current IEEE 802 committees CWNA Guide to Wireless LANs, Second Edition

  28. Wi-Fi Alliance • Wireless Ethernet Compatibility Alliance (WECA): Consortium of wireless equipment manufacturers and software providers formed to promote wireless network technology • Three goals: • Encourage wireless manufacturers to use IEEE 802.11 technologies • Promote and market these technologies to consumers at home, and in small and large organizations • Test and certify that wireless products adhere to the IEEE 802.11 standards CWNA Guide to Wireless LANs, Second Edition

  29. Wi-Fi Alliance (continued) • WECA changed name to Wi-Fi Alliance in 2002 • Reflected name of certification that it uses (Wi-Fi) to verify that products follow IEEE standards • Only products that pass Wi-Fi Alliance tests may be referred to as Wi-Fi Certified • Wi-Fi Alliance now allows businesses to apply to be registered as a Wi-Fi ZONE • Qualifies them to be placed in online database of wireless hotspot locations • Can be accessed through Alliance’s Web site CWNA Guide to Wireless LANs, Second Edition

  30. Federal Communications Commission (FCC): Responsibilities • Primary regulatory agency for wireless communications in U.S. and territorial possessions • Independent government agency • Directly responsible to Congress • Broad range of responsibilities • Develop and implement regulatory programs • Process applications for licenses and other filings • Analyze complaints • Conduct investigations • Take part in congressional hearings CWNA Guide to Wireless LANs, Second Edition

  31. FCC: Regulating the Radio Frequency Spectrum • FCC regulates radio frequency spectrum • Entire range of all radio frequencies • Spectrum divided into 450 different bands • U.S. obligated to comply with international spectrum allocations • FCC license normally required to send and receive on a specific frequency • License-exempt spectrum or unregulated bands: Bands that are available nationwide to all users • Created to foster development of new devices CWNA Guide to Wireless LANs, Second Edition

  32. FCC: Regulating the Radio Frequency Spectrum (continued) Table 2-3: Common radio frequency bands CWNA Guide to Wireless LANs, Second Edition

  33. FCC: Regulating the Radio Frequency Spectrum (continued) • Two unregulated bands used for WLANs • Industrial, Scientific, and Medical (ISM) band • Unlicensed National Information Infrastructure (U-NII) band: Intended for devices that provide short-range, high-speed wireless digital communications • Negative features of unregulated bands: • Devices from different vendors may attempt to use same frequency • Can cause interference and unpredictability CWNA Guide to Wireless LANs, Second Edition

  34. FCC: Regulating the Radio Frequency Spectrum (continued) Table 2-4: Unlicensed bands CWNA Guide to Wireless LANs, Second Edition

  35. Types of Wireless LANs • Since late 1990s, IEEE has approved four standards for wireless LANs: • IEEE 802.11 • IEEE 802.11b • IEEE 802.11a • IEEE 802.11g • IEEE 802.11n expected to be approved by 2006 HA! CWNA Guide to Wireless LANs, Second Edition

  36. IEEE 802.11 • Specified that wireless transmission could take place via infrared (IR) or radio signals • Infrared Transmissions: • Can send data by the intensity of the infrared light wave • Light spectrum: All types of light • Infrared light: Can be used for wireless transmissions • Invisible • Emitter: Device that transmits a signal • Detector: Device that receives a signal CWNA Guide to Wireless LANs, Second Edition

  37. IEEE 802.11 (continued) Figure 2-13: Directed transmission CWNA Guide to Wireless LANs, Second Edition

  38. IEEE 802.11 (continued) Figure 2-14: Diffused transmission CWNA Guide to Wireless LANs, Second Edition

  39. IEEE 802.11 (continued) • Infrared Transmissions (continued): • Advantages: • Does not interfere with other communications signals • Not affected by other signals • Does not penetrate walls • Disadvantages: • Lack of mobility • Limited range • Confined to indoor use • Slow transmission speed CWNA Guide to Wireless LANs, Second Edition

  40. IEEE 802.11 (continued) • Radio Wave Transmissions: • Radio waves can penetrate through objects • Provides mobility • Radio waves travel longer distances • Can be used indoors and outdoors • Radio waves can travel at much higher speeds than infrared transmissions • IEEE 802.11 standard outlining radio wave transmissions has become preferred method for wireless LANs CWNA Guide to Wireless LANs, Second Edition

  41. IEEE 802.11b • 802.11 standard’s 2 Mbps bandwidth not sufficient for most network applications • 802.11b amendment added two higher speeds (5.5 Mbps and 11 Mbps) to original 802.11 standard • Uses ISM band • Supports wireless devices up to 115 meters (375 feet) apart • Radio waves decrease in power over distance • 802.11b standard specifies that, when devices out of range to transmit at 11 Mbps, devices drop transmission speed to 5.5 Mbps CWNA Guide to Wireless LANs, Second Edition

  42. IEEE 802.11a • IEEE 802.11a standard specifies maximum rated speed of 54 Mbps • Also supports 48, 36, 24, 18, 12, 9,and 6 Mbps transmissions using U-NII band • 802.11a and 802.11b published at same time • 802.11a came to market later due to technical issues and high production cost • Range of 802.11a is less than that of 802.11b CWNA Guide to Wireless LANs, Second Edition

  43. IEEE 802.11g • Effort to combine best features of 802.11a and 802.11b • Data transfer rates to 54 Mbps • Support devices up to 115 meters apart • 802.11g standard specifies that devices operate entirely in ISM frequency CWNA Guide to Wireless LANs, Second Edition

  44. Projected IEEE 802.11n • Currently in evaluation stage • Top speed of 802.11n standard will be anywhere from 100 Mbps to 500 Mbps • Ratification may not occur until 2006 • Devices based on standard may appear prior to that • 802.11 pre-N CWNA Guide to Wireless LANs, Second Edition

  45. Summary • Wireless LAN devices are in many respects similar to those found in a wired network; the main difference is that wireless devices use an antenna or other means to send and receive signals instead of a wired connection • An access point (AP) is both the base station for the wireless network and a bridge to connect the wireless network with the wired network • A remote wireless bridge is a wireless device designed to connect two or more wired or wireless networks together CWNA Guide to Wireless LANs, Second Edition

  46. Summary (continued) • Standards ensure that devices from one vendor will interoperate with those from other vendors, and create competition between vendors • There are three regulatory bodies that play a major role in wireless LAN technology: the IEEE, the Wi-Fi Alliance, and the FCC • There currently are three standards or types of wireless LANs: IEEE 802.11b, IEEE 802.11a, and IEEE 802.11g CWNA Guide to Wireless LANs, Second Edition