VoIP Alternatives

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VoIP Alternatives Feature Article

September 13, 2006

Carrier Ethernet, Pseudowire and Compression--Oh My!

Mae Kowalke, TMCnet Associate Editor

This summer, RAD Data Communications introduced several new products, including a line of Metro Ethernet fiber-to-copper converters, a multiplexer for E1, and an Ethernet modem. The company, which specializes in Ethernet connectivity solutions for carriers, also recently highlighted its expansion into the Russian market.
To find out more about RAD’s products, and particularly the company’s work developing pseudowire and compression solutions, TMCnet recently spoke with Eitan Schwartz, vice president of RAD’s pseudowire and Ethernet access division. This article is based on that interview.
RAD and the Carrier Ethernet Market
RAD’s main focus, Schwartz told TMCnet, is on network access solutions for carriers. The company manufactures an extensive line of “smart jacks”—devices that act as demarcating devices between the carrier network and the customer network.
These devices help carriers use Ethernet in similar ways to traditional TDM infrastructure, while at the same time ensuring that services meet the expectations of customers.
Specifically, RAD’s devices are used by carriers to reliably deliver on service level agreements (SLAs). SLAs are documents that detail specifications about a service being provided—for example, speed and the quality of voice signal. The carrier needs a device that can measure these variables.
“This becomes even more important when there are multiple carriers involved,” Schwartz stressed.
To illustrate a multi-carrier scenario, Schwartz used the example of an enterprise that selects a single carrier for all its communications needs. In truth, that carrier does not actually own equipment needed to deliver services to all the enterprise's locations. So, it negotiates with partners to extend its footprint.
Through partnerships, the carrier is able to deliver the services, but in doing so it has to rely on someone else’s network, which may or may not perform as expected. Yet the carrier must still answer to the customer for all services involved.
In order to ensure that the SLA is fulfilled, the carrier installs one of RAD’s intelligent demarcation devices at the customer location. This device acts like a probe, talking to other devices involved in delivering the service and reporting back if there are problems. This way, the carrier can be proactive and fix problems as they occur.
Drivers for Carrier Ethernet
So, we’ve established that, thanks to RAD, carriers have access to the tools they need to deliver reliable services using Ethernet. But, one might ask, why are carriers using Ethernet to begin with?
Why indeed.
Schwartz told TMCnet that a primary driver for carrier Ethernet is cost—Ethernet can be as much as ten times cheaper than other types of networks. In large part, this is because Ethernet offers more bandwidth per circuit than other types of connections.
For example, Schwartz said, a single Gigabit Ethernet switch can carry one hundred times the bandwidth of a T1 line. He noted that Ethernet is also simpler to deploy.
As a result of these advantages—cost, bandwidth, ease of deployment—Ethernet is becoming very popular among carriers, Schwartz said. Ethernet bandwidth can be used for many applications—including VoIP and Internet connections.
Many cellular companies now are using Ethernet for backhaul, he noted. In part, this is because of the demand for high-speed data services, which require a lot of bandwidth.
“Big enterprises are looking for big Ethernet pipes," Schwartz noted.
Of course, the same amount of bandwidth can be produced by bridging together T1s, but that’s expensive because the carrier has to provision multiple lines.
Introducing Pseudowire
As great as Ethernet is, though, the restraints of existing services or infrastructures sometimes mean that carriers need T1s. In order to serve their customers, carriers could provision both T1s and Ethernet. Or, they could use RAD’s solutions to emulate T1s using Ethernet.
That’s right—a carrier can provision an Ethernet circuit, and carve out part of the bandwidth in that circuit for use as an emulated T1 line. This allows the carrier to take advantage of the cost savings of Ethernet, but still deliver cellular and other services that require T1s.
Pseudowire also makes it possible to emulate TDM circuits, Schwartz noted.
To illustrate how this might be useful, he presented an example of a school district that uses a T1 for telephone and Internet service.
In order to save money, the school decides to go with VoIP instead of traditional telephony. But, there's a problem—VoIP requires reengineering the network using new switching methods, which is expensive.
Luckily, RAD’s products offer a more affordable solution: the school can provision an Ethernet circuit, and use pseudowire to emulate TDM with part of the bandwidth. The result is that the school’s existing PBXs remain functional. Since the school doesn't have to replace its equipment, there are funds for Ethernet and the benefits of VoIP are realized.
The Power of Pseudowire
From a carrier perspective, Schwartz noted, fiber is often the preferred method of delivering network bandwidth to customers. Yet, fiber may not be available the full distance to the customer location. Instead, the carrier may have to terminate the network using copper or some other type of architecture.
This presents a problem, since fiber carries more bandwidth per circuit than copper: how can the carrier deliver the full amount of bandwidth user a “lesser” circuit?
The answer, Schwartz told TMCnet, lies in RAD’s solutions that allow carriers to bond together multiple copper circuits to create a bigger pipe, as it were.
Using products from RAD, circuit bonding can be achieved using any type of equipment, including copper, T1, and coax.
As an example, Schwartz presented a scenario in which Ethernet is used to bring 6 Megs of bandwidth almost all the way to a carrier’s customer. At a certain point, the Ethernet infrastructure ends and all that is available is T1. So, using RAD’s equipment, the carrier bonds together four T1s, which together provide the needed 6 Megs of bandwidth.
One Step Further: Compression
Of course, in some situations the architecture needed to deliver a desired amount of bandwidth simply isn’t available—or is too expensive. To solve the problem of limited bandwidth, RAD takes pseudowire a step further by introducing compression.
Compression is of particular interest to call centers, since these businesses often need to deliver bandwidth for voice internationally, which can get quite expensive.
RAD’s compression equipment, Schwartz noted, can squeeze as many as 16 calls onto a circuit designed to handle a single call. The result is a significant reduction in the number of circuits a call center has to contract for—and big savings.
Voice compression, Schwartz said, is all about saving money. For example, suppose a call center uses 16 E1 lines, at $8,000 per. Each of those lines can carry 30 calls simultaneously.
Now, consider the fact that RAD’s compression solutions make it possible for a single E1 line to carry the same amount of traffic as sixteen uncompressed lines. If the call center goes this route, it only has to provision one E1 line at a cost of $8,000 instead of 16 at a cost of $128,000.
Compression, Schwartz noted, is an excellent choice not just for call centers, but any business that uses expensive circuits.
He added that any type of compression does have an effect on the quality of voice signal. But, in RAD’s experience, the quality of compressed voice is similar to VoIP—or better.
VoIP’s Effect on Compression
There has been some speculation in the networking industry that the introduction of VoIP will reduce or eliminate the need for voice compression. But, Schwartz said that hasn’t been the case.
The reason: compression is still necessary in situations where bandwidth is expensive.
“VoIP allows you to put voice calls over IP networks,” he noted. “So does RAD’s pseudowire.”
VoIP and pseudowire both allow for compression, but since pseudowire is more efficient at performing this function, it is the better choice if the cost of bandwidth is an issue, Schwartz said.
Mae Kowalke previously wrote for Cleveland Magazine in Ohio and The Burlington Free Press in Vermont. To see more of her articles, please visit Mae Kowalke’s columnist page.

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