CWNA: Official Certification Guide Unit 1 Introduction to Wireless LANs

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1 CWNA: Official Certification Guide Unit 1 Introduction to Wireless LANs Wireless LANs were once considered expensive and slow solutions to certain network connectivity issues. Wireless LAN sales are now exploding. A recent industry publication stated that wireless network sales are the only part of an otherwise depressed network solution market actually increasing in market share. Enterprise solution vendors such as Cisco Systems and Avaya Communications, and small office/home office (SOHO) vendors, such as Linksys and D-Link, all offer some type of wireless network solution. Wireless networks are finding their way into large enterprises, such as banks and hospitals, where they help solve network connectivity challenges such as extremely long distances between network nodes and mobile user communications. Small and midsized businesses can expand their existing networks quickly and inexpensively and can have a new network up and running in less than a day. Law enforcement, fire and rescue teams, ambulatory services, and other government agencies are finding wireless LANs useful in a Wireless Metropolitan Area Network (WMAN) configuration. Finally, home users who want to share a broadband connection no longer have to pull wires or use the home electrical wiring as a networking medium. This unit discusses the wireless LAN market, presenting an overview of the past, present, and future of wireless LANs, and provides an introduction to the standards that govern wireless LANs. We discuss some of the appropriate applications of wireless LANs and introduce you to the various organizations that guide the evolution and development of wireless LANs WestNet Learning

2 Unit 1 CWNA: Official Certification Guide The knowledge of the history and evolution of wireless LAN technology is an essential part of the foundational principles of wireless LANs. A thorough understanding of the origins of wireless LANs and the organizations and applications that helped the technology mature enables you to better apply wireless LAN technologies to meet your organization s or client s needs. Lessons 1. The Wireless LAN Market 2. Wireless LAN Applications Terms 100BaseT The group of proposed IEEE Physical Layer specifications for 100-Mbps Ethernet (fast Ethernet) over various wiring specifications is referred to as 100BaseT. Fast Ethernet and the 100BaseT standard are synonymous. 100BaseT is the specification for twisted pair wiring in a Fast Ethernet environment is the IEEE standard that specifies medium access and Physical Layer specifications for 1 Mbps and 2 Mbps wireless connectivity between fixed, portable, and moving stations within a local area a a, a revision to the IEEE standard, operates in the unlicensed 5 GHz band. Most a products have data rates up to 54 Mbps and must support 6, 12, and 24 Mbps b b is a revision to the IEEE standard for direct sequence wireless LANs. Most b products have data rates of up to 11 Mbps, even though the standard does not specify the techniques for achieving these data rates g IEEE g is a proposed wireless network standard designed to provide the bandwidth of a networks while maintaining backward compatibility with b networks g operates in the 2.4-GHz ISM band. access layer The access layer provides client devices access to the network in a three-layer hierarchy network design WestNet Learning

3 Overview access point An access point is a Layer 2 (Data Link Layer) device that serves as an interface between the wireless network and a wired network and can control medium access using RTS/CTS. Access points combined with a distribution system (Ethernet, for example) support the creation of multiple radio cells (also called basic service sets [BSSs]) that enable roaming throughout a facility. Asymmetric Digital Subscriber Line (ADSL) ADSL is a relatively new technology used to deliver high-speed digital communications across the local loop over standard local loop copper wire. ADSL data rates range from 128 Kbps to over 1.5 Mbps downstream, and 64 Kbps to over 640 Kbps upstream. Asynchronous Transfer Mode (ATM) ATM is connectionoriented cell relay technology based on (53-byte) cells. An ATM network consists of ATM switches that form multiple virtual circuits to carry groups of cells from source to destination. ATM can provides high-speed transport services for audio, data, and video. basic service set (BSS) BSS is a set of compliant stations and an access point that operates as a fully connected wireless network. beamwidth Beamwidth is the measure of the horizontal and vertical lobes of an antenna signal. An omnidirectional antenna has a 360-degree horizontal beamwidth, while a semidirectional antenna may only have a 30-degree beamwidth. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) CSMA/CD is the technique Ethernet uses for controlling access to the shared transmission medium (the bus). In CSMA/CD, a node may not transmit unless the medium is idle (carrier sense). If the transmitting node detects (collision detection) that another station (multiple access) has begun to transmit at the same time, both nodes stop, then wait a random time interval before attempting to retransmit. Category 5 UTP data cable Category 5 cabling is certified for data rates up to 100 Mbps, which facilitates BaseT (Ethernet) networks. core layer In a three-layer hierarchy network design, the core layer provides access to external networks, and routes packets between distribution layers. The core layer should be fast, versatile, stable, and redundant WestNet Learning

4 Unit 1 CWNA: Official Certification Guide distribution layer In a three-layer hierarchy network design, the distribution layer moves packets between the access layers, and passes information up to the core layer. Ethernet Ethernet technology, originally developed in the 1970s by Xerox Corporation in conjunction with Intel and DEC, is now the primary medium for LANs. The original Ethernet has 10-Mbps throughput and uses the CSMA/CD method to access the physical media. Fast Ethernet (100-Mbps Ethernet) and Gigabit Ethernet (1,000-Mbps Ethernet) are also used. Federal Communications Commission (FCC) The FCC is an independent U.S. government agency, directly responsible to Congress. The FCC was established by the Communications Act of 1934 and is charged with regulating interstate and international communications by radio, television, wire, satellite, and cable. The FCC s jurisdiction covers the 50 states, the District of Columbia, and U.S. possessions. frame relay Frame relay is a packet switching technology designed to move data across a WAN. Frame relay normally operates at speeds of 56 Kbps to 45 Mbps. Gigahertz (GHz) A GHz is one billion cycles per second (hertz). highly directional antenna A highly directional antenna is one that tightly focuses the horizontal and vertical RF beamwidths to maximize the distance the propagated wave can travel. Institute of Electrical and Electronic Engineers (IEEE) IEEE is a United States-based standards organization participating in the development of standards for data transmission systems. IEEE has made significant progress in the establishment of standards for LANs, in particular, the IEEE 802 series of standards. last mile Last mile is a term used to describe the local loop. A local loop is the pair of copper wires that connects a customer s telephone to the telephone company s CO switching system. megabits per second (Mbps) Mbps identifies the rate at which information travels down a physical medium or through space (wireless). Mbps is equivalent to 1,000,000 bits per second Mbps is equivalent to 1,544,000 bits per second. omnidirectional antenna An omnidirectional (omni) antenna is one that has a 360-degree horizontal beamwidth and a variable vertical beamwidth. Omni antennas propagate the RF signal equally in all horizontal directions WestNet Learning

5 Overview personal digital assistant (PDA) PDAs are small, handheld devices that provide a subset of the operations of a typical PC. They are used for scheduling, electronic notepads, and small database applications. point-to-point (PtP) A PtP connection provides dedicated communications between two, and only two, endpoints. point-to-multipoint (PtMP) A PtMP connection connects a single point to multiple outlying points. Also known as hub-andspoke, the hub is the focal point for communications between several adjacent networks. All communications center on the hub. Request to Send/Clear to Send (RTS/CTS) RTS/CTS is a virtual carrier sense protocol used on WLANs. When RTS/CTS is enabled on a wireless LAN, a station wishing to communicate effectively reserves the medium for a period of time. All other stations then must wait for the communications to end before they can use the medium. semidirectional antenna A semidirectional antenna is one where the antenna focuses most of the radio signal energy in one direction, while creating several smaller lobes around the edges of the major signal. Semidirectional antennas are well suited for short to medium range bridging between buildings, but can also be used indoors to better direct the radio signal down halls or around obstacles. small office/home office (SOHO) SOHO is a term used to describe data and voice communications workers who either work from their home, or work in a small office of 50 or fewer workers. Token Ring Token Ring is the IEEE specified, ring-based, token-passing LAN topology. Each node on the ring acts as a repeater, passing the token from node to node as the token travels around the entire ring. Each node must wait its turn to transmit data and may only transmit when it controls the token. Unlicensed National Information Infrastructure (UNII) bands A segment of RF frequencies allocated by the FCC for unlicensed data communications, used by IEEE a, h, and HyperLAN2 wireless LANs; the three bands are: 5.15 to 5.25 GHz, 5.25 to 5.35 GHz, and to GHz. Wireless Ethernet Compatibility Alliance (WECA) WECA s mission is to certify interoperability of Wi-Fi (IEEE ) products and to promote Wi-Fi as the global wireless LAN standard across all market segments WestNet Learning

6 Unit 1 CWNA: Official Certification Guide Wireless Fidelity (Wi-Fi ) Wi-Fi is the WECA certification standard signifying interoperability among b products. Wireless Internet Service Provider (WISP) A WISP is an Internet service provider (ISP) that provides customers with access to the Internet over wireless networks. WISPs often operate in rural areas where the wired infrastructure is inadequate for providing anything but dialup Internet access. Wireless LAN Association (WLANA) The Wireless LAN Association (WLANA) is a nonprofit educational trade association, comprised of the leaders and technology innovators in the local area wireless technology industry. Through sponsor and affiliate members knowledge and experience, WLANA provides a clearinghouse of information about wireless local area applications, issues, and trends. In addition, WLANA serves as an industry resource regarding wireless LAN and PAN products, as well as to industry press and analysts. xdsl xdsl is a generic term used to describe different types of Digital Subscriber Line services WestNet Learning

7 Lesson 1 The Wireless LAN Market Lesson 1 The Wireless LAN Market The market for wireless local area networks (WLANs) seems to be evolving similarly to the networking industry as a whole, starting with the early adopters using whatever technology was available. The market has moved into a rapid growth stage, for which popular standards are providing the catalyst. The big difference between the networking market as a whole and the wireless LAN market is the rate of growth. The flexible implementation of wireless LANs makes it clear why they are outpacing every other market sector. Objectives At the end of this lesson you will be able to: Explain the general history of wireless LANs Identify standards specific to today s wireless LANs Key Point Today s wireless LAN standards evolved from the military s need for simple and secure data communications in a combat environment. History of Wireless LANs Spread spectrum wireless networks, like many technologies, came of age under the military s guidance. The military needed a simple, easily implemented, and secure method of exchanging data in a combat environment. As the cost of wireless technology decreased and the quality increased, it became cost-effective for enterprise companies to integrate wireless segments into their network. Wireless technology offered a relatively inexpensive way for corporate campuses to connect buildings to one another without laying copper or fiber cabling. Today, the cost of wireless technology enables most businesses to implement wireless segments on their network. Many companies have converted completely to wireless networks, saving time and money while allowing the flexibility of roaming WestNet Learning

8 Unit 1 CWNA: Official Certification Guide Today s Wireless LAN Standards Households are also benefiting from the low cost and subsequent availability of wireless LAN hardware. Many people are now installing cost-effective wireless networks that take advantage of the convenience of mobility and creating home offices or wireless gaming stations. As wireless LAN technology improves, the cost of manufacturing (and therefore purchasing and implementing) the hardware continues to fall, and the number of installed wireless LANs continues to increase. The standards that govern wireless LAN operation increasingly stress interoperability and compatibility. As the number of users grows, lack of compatibility may render a network useless, and the lack of interoperability may interfere with the proper operation of other networks. Because wireless LANs transmit using radio frequencies, the same types of regulations that govern such things as AM/FM radios regulate wireless LANs. The Federal Communications Commission (FCC) regulates the use of wireless LAN devices. In the current wireless LAN market, several accepted operational standards and drafts in the United States are created and maintained by the Institute of Electrical and Electronic Engineers (IEEE). Groups of people that represent many different organizations, including academics, business, military, and the government create these standards. Because IEEE standards can have a significant impact on the development of technology, the standards can take many years to be created and agreed upon. You may even have an opportunity to comment on these standards at certain times during the creation process. Wireless LAN Specific Standards The standards specific to wireless LANs are covered in greater detail in further reading on wireless LAN organizations and standards. Because these standards are the basis upon which the latest wireless LANs are built, a brief overview is provided here: IEEE the original wireless LAN standard that specifies the slowest data transfer rates in both spread spectrum RF and infrared transmission technologies. IEEE b describes data transfer rates faster than and a more restrictive scope of transmission technologies, using only Direct Sequence Spread Spectrum (DSSS) technology. This standard is also widely promoted as Wi-Fi by the Wireless Ethernet Compatibility Alliance, or WECA WestNet Learning

9 Lesson 1 The Wireless LAN Market IEEE a describes much faster data transfer rate than IEEE b (but lacks backwards compatibility), and uses the 5 GHz UNII frequency bands. IEEE g the most recent draft based on the series of standards that describes data transfer rates equally as fast as IEEE a, and boasts the backward compatibility to b required to make inexpensive upgrades possible. Emerging technologies will require standards that describe and define their proper behavior. The challenge for manufacturers and standards makers alike will be bringing their resources to bear on the difficulties of interoperability and compatibility WestNet Learning

10 Unit 1 CWNA: Official Certification Guide Activities 1. Which of the following reasons explain why wireless LANs have recently grown in popularity? (Choose three.) a. They provide increased speed over wired network solutions. b. They provide an inexpensive way to connect buildings on a corporate campus. c. They enable users to build home networks without installing network cables. d. They save time and money when building new network segments. 2. Which of the following wireless LAN standards specifies the lowest data transfer rate? a b a c b d g 3. Which of the following organizations creates and maintains the U.S. wireless LAN standards? a. FCC b. WECA c. IEEE d. IETF 4. Which of the following wireless LAN standards specifies data rates higher than, but remains backward compatible with, b? a b a c f d g WestNet Learning

11 Extended Activities Lesson 1 The Wireless LAN Market 5. Which of the following organizations promotes b as Wi-Fi? a. FAA b. WECA c. IEEE d. IETF 1. Research the history of spread spectrum wireless LANs, from their military origins to their current applications. How do the military applications differ from today s use of the technology? How are they the same? 2. Visit several wireless LAN vendor sites and compare their products. How do their products differ in features such as security, manageability, and utilities? Which vendor do you think offers the most features for the money? Which are better suited to enterprise versus home use, and vice versa? 2003 WestNet Learning