Unplugging the LAN

The recently ratified IEEE 802.11 standard for wireless Ethernet promises 2M bit/sec bandwidth at ranges of 500 feet or more - but don't believe everything you hear.

The 802.11 standard is the specification for spread spectrum wireless LAN technologies using multiple channels along the 2.4-GHz band. Its use of multiple frequencies helps prevent eavesdropping on radio traffic. The standard also adds a contention system to wireless nets, similar to the system used in Ethernet networks.

State of the wireless art Look closely and you'll find two slightly different (and incompatible) versions of 802.11 (plus an infrared version). The first, Frequency Hopping Spread Spectrum (FHSS) works by hopping from one frequency to another, staying on each channel for only 1/10 of a second. The competing technology, Direct Sequence Spread Spectrum (DSSS), works in a similar fashion by using bits of noise, called chips, to split the data stream, which the receiver has to be able to decipher on the other end. In most tests, DSSS marginally outperforms FHSS. However, products based on FHSS claim better signal stability and are less expensive. The wireless LAN industry has quickly found itself fragmented along DSSS-FHSS lines. While some vendors have been offering both technologies, most are divesting one line of products. The two camps have formed uneasy alliances, but our invitations to join this comparison went unilaterally unanswered by the FHSS camp (BreezeCOM, Symbol Technologies and Proxim), all of which cited product availability problems or offerings that were not ready for review. When the dust cleared, we had four products to review, all from DSSS vendors. How we did it We tested all the products in a real office environment. We connected each access point to a hub on our shared 10M bit/sec LAN, which hosted a Windows NT 4.0 Service Pack 4 server and several Windows 98 clients. We installed each wireless LAN adapter in an Acer Extensa 368D 233-MHz Pentium laptop with 48M bytes of RAM, running Windows 98. After configuring the LAN with the included utilities, we tested performance by copying a large file (the 23.6M-byte Microsoft Office 97 SR-2A executable patch) through Windows Explorer across the airwaves at two ranges: 32 feet and 70 feet. While you can typically achieve higher throughput by using File Transfer Protocol instead of Windows file copies, we wanted to simulate the most reasonable usage of PC Card wireless technology (for example, checking e-mail and copying files to and from the network) in a Windows environment, with all the overhead that typically entails. We also measured the ultimate range supported by traveling away from the access point with laptop in tow and noting the range where signal was lost. Because of the difficult architecture of our building, distances are estimated. We also measured how well each product assured the security of our data, through support for authentication schemes.

A flurry of new products based on 802.11 have just hit the market, but in our tests of the first standard-compliant Direct Sequence Spread Spectrum (DSSS) wireless adapters and access points, we found that none lived up to their claims of high throughput and long ranges. We also found generally disappointing administration utilities and subpar documentation.

On the other hand, interoperability testing was surprisingly smooth. All the vendors' adapters worked with the others' access points. Throughput tended to hover near the rating associated with the access point, no matter which vendor's adapter was employed.

After extensive testing, we gave Nortel Networks' BayStack 660 our Blue Ribbon on the strength of its management utilities and range, despite the product's lackluster throughput. Aironet's PC4800 was the throughput champion, but the product suffered from poor administration tools and documentation and a high price tag. Lucent's WaveLAN and Cabletron's RoamAbout 2400 - the other products we tested - are both reasonable if not outstanding products.

We saw a definite performance/range trade-off in all the products. In general, the faster the throughput, the shorter the distance that can be traveled without signal degradation and, eventually, loss. Read our story on RadioLAN's high-speed wireless network for an extreme example of this law of wireless LANs.

We did our testing in a concrete-and-steel building in San Francisco, full of radio and electronic interference. While some vendors report ranges in open-space buildings - where there are no obstacles at all between antennae - of 300 to 600 feet, we saw much smaller ranges in our stress-testing environment. This real-world environment also likely explains why performance, even at 32 feet, is substantially off the 2M bit/sec specification.

Surfing another kind of wave

Nortel's BayStack 660 package has an interesting genealogy. It started out as Netwave Technologies' AirSurfer Pro product. The company was purchased by Bay Networks, which merged with Nortel to become Nortel Networks. All packaging and labels still indicate this is a Netwave product, and all product support is available through the Netwave Web site.

Roaming with the BayStack PC Card is a pleasant network experience. If you leave the coverage area, the unit automatically reconnects you to the network when you reenter it. Of the products we tested, the BayStack had the best range at 88 feet. Unfortunately, it also had the worst performance at short range, with 1.11M bit/sec throughput at 32 feet and 0.97M bit/sec throughput at 70 feet. This isn't appalling, but it is slower than competing products.

BayStack 660's access point is housed in a flimsy piece of plastic with five unlabeled LEDs that ostensibly indicate connectivity status. It includes 10Base-T and 10Base-2 interfaces.

The Java-based setup and configuration utility for the access point is glacially slow but functionally complete. Once you launch the configuration utility, it traps the access point's periodic BOOTP requests and lets you assign a new IP address to the unit. Other advanced configuration options are probably not necessary for most users. The access point can also be managed through SNMP tools. As with all DSSS products, BayStack access points can be overlapped to provide load-balancing services and higher throughput.

While the access point management is somewhat weak, the setup and management of the PC Card clients are exceptionally good. Installing drivers and assigning an IP address to a card is a snap, and the extra utilities (especially the detailed Site Survey utility, for determining how many access points you need and where they should be located) are quite good. Overall, you should be able to get up and running with a BayStack Wireless LAN quickly and relatively painlessly. It's also simple to build an ad hoc network without an access point, if you want to share files between two Windows 95 notebooks on the train to work.

The BayStack includes a neat security feature that lets you allow and deny access on a card-by-card basis, by designating media access control (MAC) addresses.

Nortel's manuals are fair, often showing you screen shots of dialog boxes but not explaining what they do. However, the Planning Guide offers some good advice on building large wireless LANs.

Despite relatively poor performance and other flaws, the BayStack 660 came out on top of this comparison thanks to good range and exceptional client manageability. It's a good product for sites where blazing throughput is not a concern, but ease of use is critical.

An old standard

Lucent has been providing wireless networking in the form of its WaveLAN product line for more than seven years. However, with middling performance and weak management tools, the latest WaveLAN product fails to stand out.

Performance was a bit disappointing, with a 1.15M bit/sec throughput at 32 feet. However, throughput held up well at 70 feet, falling only to 1.11M bit/sec. Range was 80 feet, fair for this comparison. The card reconnects automatically after reentering the coverage area. Lucent also markets a $95 WaveLAN Range Extender Antenna, a bulky device that plugs into the the PC Card on your laptop or the access point. Using the antenna improved signal strength considerably at short ranges but had no effect on the ultimate range of our LAN.

Lucent provides 10Base-T and 10Base-2 interfaces on its WavePoint-II access point. Be careful when working with the WavePoint-II: its metal construction left our test area badly scratched.

The access point setup utilities are more of a hassle than competing products, making WaveLAN network configuration an hours-long, tedious affair. Of particular concern was a frequent problem with the access point management software timing out in the middle of uploading or downloading settings to the antenna unit.

We also found WaveLAN's client-based utilities to be less friendly than Nortel's, although they get the job done. Advanced setup options are cleanly implemented, and security by MAC filtering is supported.

Part of the usability problem stems from the WaveLAN manuals, which are like working with bad translations from some other language. The information is there if you dig long enough, but finding it is a struggle. Online help and support are better, consisting of well-organized documentation and driver updates.

Of special note with the WaveLAN product is its broad support for numerous operating systems, including MacOS. You can also add a second PC Card to the access point for extra bandwidth, a feature unique among the products in this comparison.

Still, working with the WaveLAN products can try your patience, and the fact that we had to send the first batch back to Lucent because they didn't work did not encourage us.

Cabletron . . . without the cable

Cabletron's RoamAbout 2400 wireless LAN is high-speed hardware without many usability amenities. While the RoamAbout access point came from the company's acquisition of Digital's network division, the RoamAbout PC Card is clearly an OEM version of Lucent's WaveLAN. The two PC Cards function identically and even work with each other's drivers. They also use the same client management software and an identical external antenna can be attached to either.

We were surprised when we put the RoamAbout system to the throughput test and it performed better than the WaveLAN. At 32 feet, the RoamAbout turned in a top-flight 1.35M bit/sec performance. Throughput held up remarkably at 70 feet, even when the signal had noticeably downgraded, turning in a best-of-show 1.37M bit/sec. Range topped out at 75 feet, the lowest in this comparison, but not by much. Roaming and reconnecting worked well.

The RoamAbout access point is a bizarre device. The design is awkward and requires that you mount it on a wall or balance it precariously on one end. You have to connect cables to three of the six faces of the unit, making the balancing act all the more difficult. The hardware supports 10Base-T and 10Base-2 connections.

Cabletron's management application, RoamAbout Access Point Manager, is on par with applications from other vendors. If you happen to have a Digital hub, you can use its centralized management utilities, and you can manage the access point via SNMP.

On the downside, the RoamAbout access point has vanilla security features - protocol filtering is supported, but MAC filtering is not.

While performance was good, we can't say the same about the documentation. The access point manuals often don't match the setup screens. Online help is nothing more than product brochures. Wireless newcomers will quickly find themselves lost.

All told, weaker security options, out-of-date documentation and text-based setup combine to make Cabletron's RoamAbout a poor choice for wireless newcomers. However, for experienced professionals, its top throughput makes it an attractive choice.

The not-so-friendly skies

Straight out of beta comes the Aironet Wireless Communications PC4800 Turbo DS Series 11M bit/sec adapter. While remaining compliant with the 802.11 standard, the PC4800 promises 11M bit/sec throughput at short range when connected to an Aironet access point. Our tests with the PC4800 clocked maximum throughput at 2.84M bit/sec at 32 feet and 2.22M bit/sec at 70 feet. Range topped out at 75 feet.

How does Aironet's wireless card command roughly twice the performance of its competitors? The trick is in a proprietary transfer protocol layered on top of the 802.11 standard that Aironet boasts can realistically support traffic at up to 6M bit/sec under the right conditions.

Aironet's AP4800 access point wins some points as the only access point we tested that doesn't require a PC Card to operate. It also supports 10Base-2, 10Base-5, 10Base-T and token-ring connections, and has the most stylish design in this group, with snazzy dual antennae.

Setting up the PC4800 and AP4800, however, was an exercise in frustration. For starters, the AP4800, like the Cabletron RoamAbout, requires an ASCII console for setup. But to make matters worse, rather than using a standard null modem cable, you need a nine-pin male-to-female serial cable to hook up to your administration station. This sent us off to dig through the supply closet for the right wires. After the unit is configured it can be modified through a telnet or HTTP session. We thought Aironet's client-based software also needed major work to enhance its functionality and usability, but overall, the management tools got the job done.

Installing the PC4800 PC Card in our test laptop was even more frustrating. By default, the PC4800 is set to work in 1M bit/sec mode only. You have to dig around in the network configuration to find the appropriate setting for high-speed access.

Digging through the console utilities reveals some interesting options, such as password security, SNMP support and built-in packet filtering, but you won't find these documented anywhere. The slim manual isn't much help. A mere two pages are devoted to configuring the access point, and the vast majority of the unit's settings are completely undocumented. Online help is nonexistent.

Aironet's PC Card will work with 802.11 access points and vice versa; of course, they are limited to 802.11 throughput, which we clocked at an average of 1.28M bit/sec at 32 feet. That puts Aironet just behind Cabletron, the standards-compliant speed leader, but its severe manageability and documentation problems leave us hesitant to recommend it. The fact that you'll also spend almost twice as much on an Aironet wireless LAN than on any of its competitors is not a point in its favor, either.

RELATED LINKS Scorecard and NetResults
How we ranked the units in different categories, pricing and vendor info and performance/ range summary.

Not standard, but not bad
A look at RadioLAN, which works well but doesn't support. 802.11.

What is the IEEE 802.11 Wireless Standard?
Overview from the Wireless LAN Interoperability Forum.

Null is the co-author of the upcoming Network Administrator's Reference (Osborne). He can be reached at null@ sirius.com .