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.

Free IT resource TechNet: More ways to know it, share it, and keep it running. Sponsored by Microsoft Free IT resource Attend the SOA Executive Forum: Breaking SOA Bottlenecks SOAExecForum.com/may2007 Sponsored by InfoWorld Return to special report DOWNLOAD PDF Click here to download InfoWorld's special report Extending your network

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 the balmy shores of Honolulu 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.

Click for larger view.

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.

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.

Adtran Tracer 5045 and 6420
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.