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Issue of September 2002 
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Tech Update - WLAN
WLAN: An invisible alternative

A WLAN solution is an attractive alternative, especially in places where it's difficult to install a wired LAN infrastructure. WLANs provide mobility, are easy and fast to deploy; secure, reliable, and invisible. A look at the way WLANs work and how it can benefit you. by Soutiman Das Gupta

This year saw a steady trickle of WLAN solutions into enterprises in India. Companies across verticals like manufacturing, software solution providers, and hospitality deployed WLANs in their organizations and gained substantial value from it.

Mobility has been the biggest advantage that companies have derived from the deployments. It's after all, a great utility to allow a user to carry a portable computer anywhere within the campus and access the available applications and databases. The other benefits are less time to deploy, no hassles of digging the ground to lay cables, and no getting caught in red tape in order to get a permit to dig. Moreover, WLANs are standards-based, reliable, secure, and easy to deploy. All these factors have spurred worldwide acceptance of the technology.
Although the initial investment for a WLAN solution can be higher than that for a wired LAN solution, the overall installation expenses and lifecycle costs can be significantly lower.

Gartner Dataquest estimates that the market for WLAN products is likely to expand from USD 1.5 billion in 2001 to almost USD 3.4 billion by 2005. The CAGR will be 22 percent. Unit shipments of 802.11-based wireless access points (devices for transmitting and receiving signals) totaled 1.8 million in 2001 and will rise to 4.5 million units in 2005.

Future standards
  • 802.11e - This draft specification from IEEE creates the industry's first true universal wireless standard. It offers seamless interoperability between business, home and public environments like airports and hotels. It adds QoS (Quality of Service) features and multimedia support to the existing 802.11b and 802.11a wireless standards, while maintaining full backward compatibility with these standards.
  • 802.11i - This specification is currently under consideration. It features security and mobility enhancements to the existing standards.
  • 802.11f - This specification is also under consideration. It involves the IAPP (Inter Access Point Protocol) task group.

CONFIGURATION
In a typical WLAN configuration, a transceiver (device that can both transmit and receive) connects to the wired network from a fixed location using standard cabling. This transceiver is usually called an 'Access Point'. The access point receives, buffers, and transmits data between the WLAN and the wired network infrastructure. A single access point can support a small group of users and can function within a range of a few hundred feet, depending on vendor offerings. An antenna attached to the access point is usually mounted at an elevated place. However, it may be mounted practically anywhere as long as the desired radio coverage is obtained.

End users access the LAN through WLAN adapters (wireless versions of Network Interface Cards) that are installed as PCMCIA cards in notebook or palmtop computers, and PCI cards in desktop PCs. It can also be integrated with handheld computers. WLAN adapters provide an interface between the client NOS (Network Operating System) and the airwaves via an antenna. The nature of the wireless connection is transparent to the NOS.

ALPHABET SOUP
There were a couple of WLAN standards in the beginning: 802.11b and HiperLAN2. 802.11b emerged as the most preferred choice of vendors and users due to its flexibility and features. Within a few months, just as the market warmed up to the possibilities of WLAN using 802.11b, a new standard called 802.11a arrived. And now, 802.11g, a new standard has just been introduced.

802.11b is an IEEE (Institute of Electrical and Electronics Engineers) standard, which provides a full Ethernet-like data rate of 11 Mbps. It focuses on the bottom two levels of the OSI model which are the physical layer and the data link layer. Any LAN application, NOS, or protocol, including TCP/IP, will run on 802.11 compliant WLANs as easily as they run over Ethernet.

Since its release, the 802.11b high-rate standard has been adopted by almost all of today's wireless vendors.

Consequently, wireless network adapter card prices dropped an average of 200 percent in the past 12 months.
The IEEE has also developed 802.11a, which represents the next generation of enterprise-class WLANs. It provides greater scalability, better interference immunity, and higher speed than the current technologies. It also allows higher bandwidth applications to be run simultaneously and supports more users.

Devices utilizing 802.11a are required to support speeds of 6, 12, and 24 Mbps. Optional speeds go up to 54 Mbps, but will also typically include 48, 36, 18, and 9 Mbps. In cases of both 802.11b and 802.11a, when the client device travels farther from its access point, the connection will remain intact but speed decreases. However, 802.11a has a significantly higher signaling rate than 802.11b.

802.11g is a unique technology that promises backward compatibility with 802.11b. It can transmit data via the 2.4 GHz frequency at 54 Mbps and standardize technologies among the 2.4 GHz and 5 GHz bands. It supports three modulation schemes simultaneously. Both new and existing users can connect to the network from a single access point at higher speeds.

802.11g can serve as a major upgrade to 802.11b, but the full 54 Mbps speed cannot be achieved unless 802.11g NICs are matched with 802.11g access points. It offers support for only three communication channels making it unattractive in dense areas.

SECURITY IN WLANS

A WLAN transmits data over the air using radio waves and it can be received by any WLAN client in the area served by the data transmitter. Since radio waves travel through ceilings, floors, and walls, transmitted data may reach unintended recipients on different floors and even outside the building of the transmitter. Installing a wireless LAN may seem like putting Ethernet ports everywhere, including in your parking lot. Data privacy is a genuine concern with wireless LANs because there is no way to direct a wireless LAN transmission to only one recipient.

The protocols and standards that define security are quite mature now. They are WEP (Wired Equivalent Privacy), 802.11x, and wireless VPN. However the use of a VPN is independent of any native WLAN security scheme.

WEP is an IEEE standard which uses a symmetric scheme where the same key and algorithm are used for both encryption and decryption of data. WEP can carry out access control and ensure privacy. It performs access control by preventing unauthorized users, who lack a correct WEP key, from gaining access to the network. It ensures privacy because it protects WLAN data streams by encrypting them and allowing decryption only by users with the correct WEP keys.

Support for WEP with 40-bit encryption keys is a requirement for Wi-Fi (Wireless Fidelity) certification by WECA (Wireless Ethernet Compatibility Alliance). Some vendors implement the computationally intense activities of encryption and decryption in software, while others use hardware accelerators to minimize the performance degradation of encrypting and decrypting data streams.

802.11x is a standard of defining port-based authentication and key distribution for wired and wireless networks. It's based on a protocol called EAP (Extensible Authentication Protocol) which facilitates the authentication process between the authenticator (access point) and the suppliant (NIC of the user computer).

Once the server approves access an additional authentication process like LEAP (Lightweight Extensible Authentication Protocol) verifies the user based on a digital certificate and then dynamically generates WEP keys. 802.11x enhances WEP by changing the shared keys as often as the network manager desires but the drawback is that it is still based on the 40-bit encryption level of WEP.

Wireless VPN - VPNs have provided security for many wired LANs and may eventually provide the same protection for WLANs as well. A VPN secures a connection by acting as a boundary between the enterprise LAN and the Internet. Through integration with firewall software VPNs can offer authentication, privacy, access control, and traffic shaping capabilities to control bandwidth consumption. Companies can now implement a VPN through a VPN gateway to enhance security over WEP, but do not allow for much customization. New software products are being developed that involve unique policy-based controls to meet the different needs of each company.

What to consider before implementation

Now that you plan to implement a WLAN solution in your enterprise, here are some aspects to consider before making the buying decision.

Range and coverage: The distance over which the transmission can travel depends on the transmission power and receiving capabilities of the transceiver. It also depends on the path to be taken for the data. Interactions with typical building objects like walls, metal, and even people, can affect how energy propagates. This limits the range and coverage of a particular system.

Throughput: Throughput is affected by the number of users, range, the type of WLAN system used, latency and bottlenecks on the wired portions of the LAN. You may recall that state-of-the-art V.90 modems transmit and receive at optimal data rates of 56.6 Kbps. In terms of throughput, a WLAN operating at 1.6 Mbps is almost thirty times faster.

Compatibility with the existing network: Most WLANs provide industry-standard interconnection with wired networks that use Ethernet or Token Ring. WLAN nodes are supported by NOSs with the help of appropriate drivers just like any other LAN node. Once installed, the network treats wireless nodes like any other network component.

Interoperability of Wireless Devices: WLAN systems from different vendors may not interoperate for many reasons.

They use different frequency bands, different vendors have different implementation procedures, and different products may use different standards.

You can look for Wi-Fi certified products. WECA is an organization behind Wi-Fi that certifies products meeting the 802.11b specification through compatibility testing.

Licensing Issues: WLANs are typically designed to operate in portions of the radio spectrum where government regulatory bodies do not require the end-user to purchase a license to use the airwaves. Look for a WLAN manufacturer who is certified by the appropriate agency.

Security: Since your data travels in the air, security provisions are typically built into WLANs. This makes WLANs more secure than many wired LANs. It is extremely difficult for unintended receivers to listen in on WLAN traffic. Complex encryption techniques make it impossible for all but the most sophisticated to gain unauthorized access to network traffic.

Cost: A WLAN implementation includes infrastructure costs for the wireless access points and user costs for WLAN adapters. The cost of installing and maintaining a WLAN is generally lower than the cost of installing and maintaining a traditional wired LAN. A WLAN eliminates the direct costs of cabling and the labor associated with installing and repairing it.

Safety: The output power of WLAN systems is much less than that of a handheld cellular phone. Even then, WLANs must meet stringent government and industry regulations for safety from radiation. However, no adverse health affects have been attributed to WLANs, so far.

Soutiman Das Gupta can be reached at soutimand@networkmagazineindia.com

 
     
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