How many times have you needed network or Internet access at home and wished you could work in a different room, or even outside, without having to run a long Ethernet cable? How many times have you been in a public spot, such as an airport or hotel, and realized you needed to send a quick e-mail? How many hours have you wasted sitting in conference rooms between meetings while your e-mails pile up?
If you are like thousands of other corporate network users, telecommuters, business travelers, and home users, the answer is more than once. Network users take heed: 802.11-based WLANs hold the answer for you. 802.11-based networks provide the much sought-after mobility and bandwidth that network users have been asking for.
WLANs are not a new concept. They have been around for decades. The 802.11 standard was ratified in 1997, so why is it that WLANs are really starting to take off now? The answers are bandwidth and cost. Early wireless networks, such as Aloha, ARDIS, and Ricochet, offered data rates of less than 1 Mbps. The 802.11 standard offers vendor interoperable rates as high as 2 Mbps. The ratification of 802.11b in 1999 raised the bar to 11 Mbps, competing against wired 10 Mbps Ethernet rates. The 802.11a and 802.11g standards offer data rates as high as 54 Mbps, giving wired Fast Ethernet a run for its money.
As early implementers of WLANs, vertical industries such as retail stores, healthcare providers, and manufacturers see the value that WLANs and wireless applications bring. Many of these industries rely on WLANs as core components of their business. As a result, vendors are rising to meet the challenge of delivering cost-effective WLAN solutions for these customers. Vendors can increase their manufacturing volumes and lower their costs and as a result their prices, making WLAN hardware available to consumer and enterprise customers at reasonable prices.
Although 802.11 networks are a LAN topology, they present new challenges to network administrators who are accustomed to a world of wires and wired-based network technologies such as 802.3 Ethernet networks. Issues like site surveys, security, QoS, and network-device mobility require attention that a network administrator might not have the experience to give.
The premise to this book is to discuss the aspects of 802.11 in terms that IT and network engineers can relate to. This book is a reference guide to operating and troubleshooting 802.11 networks and also serves as the first stepping stone to bridge the gap between wired and wireless networks.
Beginning in Chapter 1, “Ethernet Technologies,” we cover the different flavors of Ethernet networks, from 10 Mbps Ethernet to Gigabit Ethernet. This chapter provides a review of Ethernet as a point of contrast for you as you continue with this book. Examining a simple yet mature technology should give you some perspective on the challenges of deploying and planning 802.11 WLANs.
Chapter 2, “802.11 Wireless LANs,” provides an overview of the technology in the frame of reference of Ethernet. It provides an overview of the 802.11 wireless Media Access Control (MAC) layer while detailing the basic functions that it performs.
Chapter 3, “802.11 Physical Layer Technologies,” overviews the physical layer (PHY) technologies used to create the 802.11, 802.11b, 802.11a, and 802.11g physical layers. They are reviewed in the context of the basic building blocks of radios. We also present the specific interface between the MAC and the PHY that has allowed the easy expansion of newer PHYs.
Chapter 4, “802.11 Wireless LAN Security,” provides a primer on security, including authentication and encryption. This information is a prelude to examining security as defined in the 1997 802.11 standard and its associated vulnerabilities. This chapter also provides details on the 802.11i draft standard for wireless security and a look at WiFi Protected Access (WPA) and interim vendor-interoperable WLAN security specifications.
Chapter 5, “Mobility,” describes the mobility of 802.11 client devices, with specific focus on how wireless applications directly impact access point (AP) deployment. Client mobility impacts the 802.11 MAC protocol but also has an impact on IP-based networks, so a brief discussion of mobile IP is also included.
Chapter 6, “QoS for 802.11 Wireless LANs—802.11e,” discusses the challenges of deploying wireless applications that require low-latency network connectivity, such as Voice over IP (VoIP). This chapter provides an overview by examining the 802.11 protocol and taking a sneak peak at the forthcoming 802.11e 802.11 QoS standard.
Chapter 7, “Radio Frequency Essentials,” overviews the essentials of radio technology as it applies to WLANs. Topics include antennas, receivers, and radio system performance. We discuss different unlicensed frequencies used throughout the world. The intent of this chapter is to provide you with the knowledge to evaluate the physical layer performance of different vendors radios.
Chapter 8, “Deploying Wireless LANs,” considers the deployment aspects of a wireless network from the physical layer through the application layer. First considering the applications to be used, it derives the requirements for the lower layers while providing specific network-setting suggestions. We discuss coverage- and capacity-oriented WLANs. This chapter outlines several different approaches to the site survey process while indicating the necessary tools for a successful survey. We detail the deployment aspects of your WLAN security policy and the tools for managing your network.
Chapter 9, “The Future of Wireless LANs,” provides a glimpse at technology trends. The specific technologies considered are Bluetooth, Ultra Wide Band, Free Space Optics, and future higher-speed 802.11 technologies.
Chapter 10, “WLAN Design Considerations,” steps through several WLAN application areas while providing insight into their unique requirements. The application areas are retail stores, healthcare organizations, branch offices, and education organizations. Also considered are scenarios that are likely to use client devices from multiple vendors. We detail the specific potential pitfalls of WLANs for remote locations. We delineate design considerations for public access networks and the unique requirements of WLANs for public-safety entities.
One thing to note: The WLAN industry is moving at an exponential pace. With each passing day, new innovations from vendors are making WLANs more secure; easier to deploy and manage; and, most importantly, more cost-effective. This book is not designed to be a finite description of WLANs. Its goal is to provide the fundamental foundations necessary for you, the network administrator, to understand how to plan, deploy, and operate a WLAN. We chose the topics and examples from real-world problems we have encountered in internal product development at Cisco Systems and from the many companies that are evaluating or actively deploying WLANs.