Bridging connectivity gaps

Bridging connectivity gaps

IT infrastructure requirements can shift quite suddenly. Say, for example, your company lands several large new accounts at the same time. The sudden influx of sales and account management staff so quickly outstrips your office's square footage that the only reasonable thing to do in the time available is to look for additional space. That space turns out to be a mile or so down the street. As an IT administrator, you need to get the new location connected to the network as soon as possible.

One option is WAN lines, but they are expensive and often require an unmanageable lead time to set up. Security risks may also be a factor, even for a virtual circuit configuration. Yet another wrinkle might be a mission-critical application, which absolutely requires more than one fat pipe path between the primary and secondary locations. T1s or T3s might suffice for the main link, but what about the backup?

In this expansion scenario, you would sooner or later turn to wireless bridging. A specialty set of products, wireless bridges connect buildings or campuses with bandwidth comparable to that of high-end leased lines.

Most IT administrators have shied away from wireless bridges. Maintaining lasers or microwave installations, and connecting them back to local networks, usually requires a combination of black magic and engineering. Consultant expenses for maintaining long-term infrastructure health can rack up quickly. Moreover, these devices have so far been costly and difficult to configure. And they have taken as long to obtain as it takes a provider to configure a T1 virtual circuit.

Even more critical is the issue of latency. New applications want to use new technologies such as streaming video or VoIP, which require not only goodly portions of fat pipes, but also fast hop transitions with latency measured in milliseconds. Wireless broadband isn't known for these traits.

But wireless bridges are now coming into their own. Manufacturers have spent the past several years revamping their product lines, claiming to have notably improved ease of use, latency, and especially cost.

To prove their worth, we invited several well-known vendors to participate in a wireless-bridging shoot-out conducted at the world-famous ANCL (Advanced Network Computing Laboratory) at the University of Hawaii. Four vendors worked up the necessary courage: Adtran, Canon, LightPointe, and Orthogon Systems. Collectively, this foursome represents the three major wireless-bridge media: microwave, RF, and optical.

We then presented the vendors with the following challenge: Implement two fast site-to-site connections, first a short hop across the ANCL parking lot (about 50 feet), which we dubbed our short-haul test, and then a longer, campus-to-campus jump (about 1.2 miles), dubbed our long-haul test.

Additionally, we added a low-latency test, using VOIP testing tools from Brix and Spirent to ensure these devices could reasonably compete with today's software requirements. These tools had the sensitivity to not only measure total bandwidth, but also to test traffic latency right down to the microsecond.

We had several requirements for our tests. First, the links had to shoot through double-pane, energy-efficient glass, which proved challenging for most of the products. Second, latency and jitter performance had to be robust enough to support VoIP traffic without an additional PBX. Finally, range and security had to be good enough to allow implementation without needing added repeaters or external VPN links for security.

Standing up to the challenge

We were pleasantly surprised by this new crop of wireless wheat. Though the products had performance and management differences, none had any trouble handling our testing suite. That, plus the ability to easily integrate with local wired infrastructure, as well as some surprisingly attractive price tags, put wireless-bridging infrastructure much higher on our list of favorite hardware than it once was.

Yes, Adtran does more than multiplexers. Indeed, the company sports a large line of networking products that covers the gamut of routing, switching, and wireless-bridge boxes. Adtran's two products, the Tracer 5045 and the Tracer 6420, were a pleasant surprise, both from a price perspective and considering their ease of use.

The products look alike and use the same style of microwave antenna. The main difference is flexibility: The Tracer 5045 represents an older yet highly reliable form of connectivity, whereas the 6420 represents a newer and more cutting-edge, modular approach.

The 5045 is designed as a 90Mbps bridge with a distance limitation of about 25 miles point-to-point. The 6420 is housed in a similar case but has a modular design, allowing it to use a variety of connectivity cards, including T1, E1, and Ethernet. The 6420 has the same range as the 5045 but an aggregate throughput of 33.6Mbps. This is offset, however, by its modular architecture, which allows you to customize the unit's capabilities and cost much more readily than you can with the 5045.

It seems the designers of both products assumed that all electronics would be located indoors; neither product is weather-resistant. This affected neither our partially indoor short-haul test nor our entirely outdoor long-haul test. Adtran also assumes you have upward of 30 feet of antenna cable leading to the outside, which means you'll have decent flexibility in terms of positioning.

The two products use similar management methods. Initially we were put off because the units indicated signal strength with an external multimeter instead of a Web-based management utility. But this approach reduces the cost of the units, and the multimeter console adequately indicated signal strength for both sides once they were linked. Of all the units we looked at, Adtran's products were easiest to get linked.


Ongoing management is both simple and practical. The system uses VT-100s to display link status, activity, and a table of power settings. These systems also default to two channels to avoid conflict and allow multiple radios to be operational at the same time. Indeed, the Tracers are designed to allow network managers to easily daisy-chain several boxes for truly long hauls, while still managing each of them from a central location.

For dedicated network managers, Adtran doesn't stop there. Customers also get access to a special section of Adtran's Web site, which contains a number of interesting tools. Customers get access to Adtran's virtual lab, where they can take Telnet-based control of running hardware in Adtran's labs. This allows customers to take Adtran equipment for a test drive over the Web -- no canned demo, but actual working equipment. The company also provides downloadable link-analyzer software, which allows owners of Adtran equipment to perform tasks such as intelligent traffic analysis for diagnostic or capacity-planning purposes.

Although we'd love to see a gigabit-capable version of the Tracer, we were plenty impressed with the series' combination of a low price and a five-minute setup easy enough for any IT manager. Both Adtran Tracers impressed us as solid options for site-to-site connectivity, with the 5045 being an excellent fixed-throughput option and the 6420 providing flexibility for organizations with independent needs.

Canon almost didn't manage to play in our shoot-out. Not only were they the last company to accept the invitation, but they were also the only company not to send hardware engineers to ensure a successful test. In Canon's favor, however, this posed no problem for the DT-110, a member of Canon's Canobeam DT-100 family; it managed all of our tests with aplomb.

On the LAN side, this system acts like a fiber-optic pipe. Different models within the DT-100 family accept a wide variety of signals, including 25Mbps for old-style ATM connections, 155Mbps for ATM OC-3, 100Mbps for Ethernet, and 1.25Gbps for Gigabit Ethernet. Even sweeter, though the DT-110 is a laser-based unit, it did not require us to convert speeds or protocols as the LightPointe product did. We simply plugged it in and were off and running.

The Canobeam was also the only laser in our roundup able to shoot through our double-paned, energy-efficient glass. In fact, we had to downshift the laser from full-power mode to low-power mode to avoid overwhelming the optics, which says a lot about this unit's potential flexibility.

As far as the lasers went, Canobeam also had the best alignment system we saw. Canon touts this feature as one of Canobeam's major draws. Each tripod is equipped with small vernier controls, which made slight adjustments really easy. So initial alignment of the two lasers was a quick process. Once we had a few bars indicating a proximity signal, we just hit the Auto Tracking button and the signal strength jumped.

The fragile nature of optic-signal alignment makes the Auto Tracking feature particularly compelling. Bad weather, wind, or even an animal deciding to perch on the equipment can misalign an optic connection badly enough to require recalibration. The DT-110's Auto Tracking feature, however, is in constant mode, meaning the connection is always confirming its own integrity. The only limitation is that the Canobeam has a restricted range for all this ease of use, forcing us to stay within 2 kilometers for Auto Tracking to work.

Our wish list for the Canobeam starts with a dedicated management package. Other products in this test provided their own Web-based management pages and even their own spectrum analyzers. The Canobeam supports SNMP for monitoring and can be monitored or even reconfigured using Telnet, and you can download diagnostic logs to management workstations as well, but this requires a manual FTP operation.

These bare-bones management features suffice; they wouldn't hinder our enthusiasm to buy the Canobeam. But they were Spartan. We would have preferred a few HTML screens that would allow us to centralize and secure these functions more easily. HTML screens would be especially welcome if we were managing a larger number of Canobeams. And Canon, after all, is not a company we think of as skimping on frills.

Seeing the light

The Canobeam was at the top of the heap for our laser line. LightPointe has a good product with superior management capabilities, but the DT-110's Auto Tracking feature and wide array of bandwidth inputs, as well as the ease with which it connects to those inputs, do much to raise the product in our eyes.

Founded in 1998, LightPointe is another young player in the wireless-bridging market. Even so, the company has come a long way very quickly with innovative and powerful optical wireless-bridging products.

LightPointe brought two product families to our shoot-out: the FlightLite and the FlightStrata. The FlightLite is a single-beam, fixed-laser system aimed at short-haul outdoor links ranging from 350 meters to 1,000 meters. The unit supports 15Mbps, 100Mbps, and 1.25Gbps network-side connectivity via optical or copper-cable connects. Additionally, the laser ran just fine using the PoE (Power over Ethernet) functionality of one of ANCL's Netgear switches.

LightPointe brought to the short-haul test was configured with only 100Mbps Ethernet connectivity, but it was light and easy to set up. Its mounting gear is heavy-duty, and it was easy to see that LightPointe paid good attention to the details, including waterproof grommets where cables enter, to keep water out of the unit.

LightPointe also brought to the test a FlightLite G, which is essentially the same unit as the FlightLite 100, except it's configured with gigabit-capable optical and copper inputs. The only other difference is that the G requires an external power supply whereas the 100 supports itself using the Netgear's PoE capability.

For our long-haul test, LightPointe broke out its state-of-the-art product: the FlightStrata. This is a multibeam unit with array-tracking capabilities as well as optical-beam-shaping features, both of which mean the FlightStrata can better recover automatically from slight misalignments and atmospheric interference. It also means that if a bird, for example, crosses the path of the beams, it interrupts only one beam at a time, so the two beams provide true uninterrupted service.

Both units used a combination of visual and audio features for setting up initial tracking. The FlightStrata turned out to be slightly more difficult to set up than the FlightLite. Once we got the initial audio tone indicating proximity, the two nodes tracked each other quickly, though they were definitely the slowest of the group.

LightPointe doesn't provide its own mounting hardware, instead offering customers a choice of third-party mounting hardware depending on the intended environment. Additionally, although the FlightLite and the FlightStrata can be used indoors and outdoors, both systems were definitely designed for outdoor use.

On the management side, LightPointe provides its own Web-based configuration and monitoring utility. Although the management utility looked a little raw, it was way ahead of the other laser in the roundup, the Canobeam. The management tool is designed for administration security and managing multiple LightPointe products, so you can manage a chain of FlightLites or FlightStratas from a central console.

Since we completed our tests, LightPointe released a version of the FlightStrata based on a patent-pending dual-path system architecture. Dubbed the FlightStrata XA, it combines the optical power of the FlightStrata with an RF-based link the system uses for seamless fail-over in case of extreme weather conditions, for example. This provides physical layer redundancy in a single package for little additional cost.

LightPointe has manufactured two product lines capable of competing with a player such as Canon, which has worked the optical space for decades. Although LightPointe bridges are definitely more difficult to set up than is the Canobeam, and although the FlightStrata is slightly more expensive, both LightPointe bridges are as robust and far easier to manage once they're configured. And LightPointe's dual-path architecture should make subsequent versions of the FlightStrata even more competitive next to single-path products such as the Canobeam.

Orthogon was a new name to us, and, indeed, the Waltham, Mass.-based company is only a few years old. Its executives, however, all have extensive background in manufacturing RF-based networking devices, and that's precisely Orthogon's focus.

Orthogon brought two products to our test, the OS-Gemini I and the OS-Spectra. Gemini is Orthogon's slightly older, more mature product line, defined mainly by its bandwidth limitation of 33.6Mbps and need for a 10/100 copper interface back to the network. The Spectra is Orthogon's newest release, capable of 10 times the throughput of the Gemini and able to run fiber uplinks back to the wired world.

The OS-Gemini runs in the 5.8GHz range and handles throughput of as much as 33.6Mbps. The product handled our short-haul jump just fine, but its latency numbers were the highest in the test. This could be attributed to the office glass in between the connection. The resulting multipath errors caused the unit to do a lot of retransmitting, giving it a higher latency score.

The initial Gemini configuration for the short-haul test came with the radio and antenna on one big flat panel. To go to a high-gain long-haul configuration, Orthogon replaced this configuration with one where the front flat antenna plate broke out the antenna leads. These leads could then be run to wave guides or higher-gain antenna systems for additional range and flexibility.

Mounting the Gemini is straightforward, but the product uses an older style of mounting hardware, including an easy-to-loose nut in the back. This increases the risk of dropping the whole rig while you're precariously perched up a radio tower. The newer hardware used on the Spectra employs a hanger rather than a nut, making it less likely that you'll drop the hardware during installation.

The OS-Spectra is definitely Orthogon's state-of-the-art offering. Also operating in the 5.8GHz range, this bridge supports both IP and circuit-switched networks with latency comparable to the other bridging media. In addition, the Spectra handles data rates of as much as 300Mbps and carries improved interference capabilities using dynamic frequency selection and adaptive modulation techniques. All this may sound confusing, but it's easily configured with a laptop tool. The Spectra also has WiMAX compatibility, which will become increasingly important as a low-cost backup-path technology as its penetration increases during the next few years.

Non line of sight

Finally, the fanciest Spectra feature allows it to bend its signal around buildings and other obstacles during long-haul hops. That means the Spectra doesn't require clear line of sight in order to function.

During our long-haul test, the Spectra managed full bandwidth in one direction, but only half bandwidth on the return trip. With some tweaking to the configuration, however, we easily solved that. The only limitation we found with this feature is that you need to give the waveform a chance to fully form, so don't try to bend around buildings too close to you.

Our wish list for Orthogon's products is only two items long. First, the company needs to change its aiming system. These products shared a truly obnoxious aiming system that indicated signal strength by the pitch of the tone transmitted through a set of earphones worn by the hapless technician. The more grating the sound (like a missing-keyboard-error beep extended and then run through a shredder), the better the overall signal.

Second, we'd love to see a lower price. These products took the longest to configure, had the highest overall latency (though still at acceptable levels even for VoIP applications), and they had the highest price.

These wishes aside, Orthogon shows that RF is still very much in the game. Optical may have the edge in speed, but Orthogon keeps RF alive in speed tests and takes RF's angle, range, and reliability options to a whole new level. For tight urban scenarios or other challenging environments, Orthogon is definitely a solution to consider.

We chose our competitors carefully, making sure to find representatives of all three major wireless-bridging media: RF, microwave (a close RF relative), and optical. After using all three types in the real world of Honolulu last February, we have a far more favorable impression of wireless bridging than we did prior to testing.

First, all these products can be configured by even general IT managers, with the RF products definitely the easiest of the bunch. Second, their prices are well within the realm of mainstream wired infrastructure, and all of them are readily available -- easily competing with the average six-week lead time for installing leased WAN lines.

Third, although we were worried about security, the optical products turned out not to pose as high a security risk as we had thought: Their beams are so tight, they're practically impossible to tap. RF doesn't share this advantage, but both our RF contenders provide VPN compatibility or optional encryption protocols (typically AES [Advanced Encryption Standard] or 3DES).

Our last worry concerned, quite naturally, the elements. These include the impact of weather on the transmission media, the hardware, and the mounting brackets. We also had two more esoteric considerations. Double-paned, tinted security glass that graces many office buildings and the proximity of other wireless infrastructures can raise serious obstacles.

Thankfully, our fears were mostly allayed. All the vendors did significant work to improve their resistance to the elements. RF is practically weather-immune, but optical is no slouch either. Lasers are affected only by truly huge raindrops or dense fog, and the proximity of other laser links doesn't affect them. Unfortunately, other RF transmitters in the same area does hamper the effectiveness of RF.

Lasers have a much easier time reaching gigabit throughput speeds, and their latency numbers were well below the numbers of their RF cousins. The only other downside to the optical products is that they're a little less flexible when it comes to extreme angles. If your point-to-point connection has both line of sight and a relatively straight shot, optical is for you. But for urban situations where more extreme angles are required, RF is a more effective choice.

Taking all these considerations into account, we find that wireless bridging has come a long way from its consultant and black-magic roots. These products proved not only stable and cost-effective, but also surprisingly easy to manage. For situations where leased lines won't cut it, wireless bridging is definitely a mainstream alternative.

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