Lesson 3 - Wireless

WLAN

Definition: AWLAN provides wireless network communication over short distances using radio or infrared signals instead of traditional network cabling.

A WLAN typically extends an existing wired local area network. WLANs are built by attaching a device called the access point (AP) to the edge of the wired network. Clients communicate with the AP using a wireless network adapter similar in function to a traditional Ethernet adapter.

Network security remains an important issue for WLANs. Random wireless clients must usually be prohibited from joining the WLAN. Technologies like WEP raise the level of security on wireless networks to rival that of traditional wired networks.

Also Known As: wireless LAN

Examples:

For WLANs that connect to the Internet, Wireless Application Protocol (WAP) technology allows Web content to be more easily downloaded to a WLAN and rendered on wireless clients like cell phones and PDAs.

WEP - Wired Equivalent Privacy

Definition: WEP is a standard network protocol that adds security to 802.11 Wi-Fi networks at the data link layer (OSI model Layer 2). WEP was designed to give wireless networks the equivalent level of privacy protection as a comparable wired network. However, the underlying technology behind WEP has been demonstrated to be relatively insecure compared to newer protocols like WPA.

WEP utilizes a data encryption scheme called RC4 with a combination of user- and system-generated key values. The original implementations of WEP supported encryption keys of length 40 bits and 24 additional bits of system-generated data (64 bits total). In an attempt to increase protection, these encryption methods were extended to support longer keys including 104-bit (128 bits of total data), 152-bit and 256-bit.

When communicating over a Wi-Fi connection, the protocol encrypts the data stream using these keys so that it is no longer human readable but still can be processed by receiving devices. The keys themselves are not sent over the network but rather are generally stored on the wireless network adapter or in the Windows Registry.

WEP represents just one element of an overall wireless network security strategy.

WPA - Wi-Fi Protected Access

Definition: WPA is a security technology for Wi-Fi wireless computer networks. WPA improves on the authentication and encryption features of WEP (Wired Equivalent Privacy). In fact, WPA was developed by the networking industry in response to the weaknesses of WEP.

WPA provides stronger encryption than WEP through use of either of two standard technologies: Temporal Key Integrity Protocol (TKIP) and Advanced Encryption Standard (AES). WPA also includes built-in authentication support that WEP does not offer. Overall, WPA provides comparable security toVPN tunneling with WEP, with the benefit of easier administration and use.

A variation of WPA designed for use on home networks is called WPA Pre Shared Key or WPA-PSK for short. WPA-PSK is a simplified but still powerful form of WPA. To use WPA-PSK, a person sets a static key or passphrase as with WEP. But, using TKIP, WPA-PSK automatically changes the keys at a preset time interval, making it much more difficult for hackers to find and exploit them. Another variation of WPA called WPA contains other technical enhancements.

Wi-Fi - Wireless Fidelity

Definition: Wi-Fi is the industry name for wireless LAN (WLAN) communication technology related to the IEEE 802.11 family of wireless networking standards. To some, the term Wi-Fi is synonymous with 802.11b, as 802.11b was the first standard in that family to enjoy widespread popularity. Today, however, Wi-Fi can refer to any of the established standards: 802.11a, 802.11b, 802.11g and 802.11n.

The Wi-Fi Alliance (see sidebar) certifies vendor products to ensure 802.11 products on the market follow the various 802.11 specifications. Unfortunately, 802.11a technology is not compatible with 802.11b/g/n, so Wi-Fi product lines have been somewhat fragmented.

802.11b

Definition: 802.11b is a Wi-Fi wireless network communication technology. It is one of the 802.11 series of IEEE standard technologies and was widely used in first-generation Wi-Fi home networking products after its introduction in 1999. 802.11b has since been rendered obsolete by the newer Wi-Fi standards 802.11g and 802.11n.

802.11b Performance

802.11b LANs support a theoretical maximum data rate of 11 Mbps. Although comparable to traditional Ethernet (10 Mbps), its performs significantly slower than newer Wi-Fi and Ethernet technologies including 802.11g and Fast Ethernet.

802.11b and Wireless Interference

Transmitting in the unregulated 2.4 GHz frequency range (like 802.11g), 802.11b transmitters can encounter radio interference from other wireless household products like cordless telephones, microwave ovens, garage door openers, and baby monitors.

802.11a

Definition: 802.11a is a Wi-Fi wireless network communication standard. It is one of the IEEE standards in the 802.11 series.

802.11a Performance

An 802.11a wireless network supports a maximum theoretical bandwidth of 54 Mbps, a noticeable advantage over 802.11b Wi-Fi that supports 11 Mbps and on par with 802.11g performance. However, 802.11a installations historically were limited to corporate environments due to comparatively higher hardware equipment costs.

802.11a and Wireless Interference

802.11a transmits radio signals in the frequency range above 5 GHz, a part of wireless spectrum regulated in many countries. This regulation means 802.11a gear generally avoids signal interference from other consumer wireless products like cordless phones. In contrast, 802.11b/g utilizes frequencies in the unregulated 2.4 GHz range and is much more susceptible to radio interference from other devices.

Range of 802.11a Networks

Though it helps improve network performance and reduce interference, the range of an 802.11a signal is limited by use of the high 5 GHz frequency. An 802.11a access point transmitter may cover less than one-fourth the area of a comparable 802.11b/g unit. Brick walls and other obstructions affect 802.11a wireless networks to a greater degree than they do comparable 802.11b/g networks.

802.11g

Definition: 802.11g was ratified in 2003 as an IEEE standard for Wi-Fi wireless networking. 802.11g supports wireless local area network (WLAN) communications among computers, broadband routers and many other consumer devices. It replaced the older 802.11b technology.

802.11g Performance

802.11g Wi-Fi supports maximum network bandwidth of 54 Mbps compared to 11 Mbps for 802.11b and 150 Mbps or more for the newer 802.11nWi-Fi.

802.11g Radio Signaling

To maintain backward compatibility with older Wi-Fi network equipment, 802.11g uses the same 2.4 GHz range of communication frequencies as 802.11b.

802.11n

Definition: 802.11n is an IEEE industry standard for Wi-Fi wireless local network communications, ratified in 2009. 802.11n is designed to replace the older 802.11a, 802.11b and 802.11g Wi-Fi technologies.

Key Wireless Technologies in 802.11n

802.11n utilizes multiple wireless antennas in tandem to transmit and receive data. The associated term MIMO (Multiple Input, Multiple Output) refers to the ability of 802.11n and similar technologies to coordinate multiple simultaneous radio signals. MIMO increases both the range and throughput of a wireless network.

An additional technique employed by 802.11n involves increasing the channel bandwidth. As in 802.11a/b/g networking, each .11n device uses a preset Wi-Fi channel on which to transmit. Each .11n channel will use a larger frequency range than these earlier standards, also increasing data throughput.

802.11n Performance

802.11n connections support maximum theoretical network bandwidth up to 300 Mbps depending primarily on the number of wireless radios incorporated into devices.

802.11n vs. Pre-N Network Equipment

In the last few years before 802.11n was officially ratified, network equipment manufacturers sold so-called pre-N or draft N devices based on preliminary drafts of the standard. This hardware is generally compatible with current 802.11n gear, although firmware upgrades to these older devices may be required.