Tips for a successful VoIP conversion

A VoIP expert at a national voice and data carrier draws on his experience to help smooth the transition

In recent years, voice over IP (VoIP) has become a byword in Global 2,000 organizations. Increasing numbers of corporations worldwide are moving their voice traffic off aging private branch exchanges to unify communications on a single network and gain the advantages of integrating voice with key applications such as customer relationship management.

Inevitably, this trend is moving into midrange organizations and will become a standard part of data network traffic in the next decade. It's also an important part of service-oriented architectures.

With this in mind, Randy Nicklas, chief technology officer of XO Communications, offers the following suggestions for networking executives facing an internal conversion to VoIP, based on his extensive experience. XO is a national business voice and data carrier with more than $1.4 billion in annual revenue. Its network carried more that 15 billion minutes of VoIP traffic last year. Commercial VoIP carrier Vonage Holdings Corp. is one of its wholesale clients. However, while XO will resell VoIP equipment to its business customers, it is agnostic concerning brand, supplying whatever switches its customer requests, and it does not sell internal services to business, making it a disinterested party in internal VoIP projects.

1. Upgrade old network components: To run well, VoIP needs a modern switched Ethernet infrastructure that can support high data volumes and class-of-service prioritization. "A 10Mbit/sec. Internet hub that has been chugging along for years won't make it," Nicklas says.

Tip: Nicklas says all the leading Ethernet switch vendors provide proven technology, so if you are facing an extensive network upgrade, talk to two or three, and make sure they know about one another. When Cisco Systems Inc. representatives come to visit, have an Avaya Inc. coffee mug on your desk, and vice versa. That will go a long way toward getting you the best discounts.

Discounts depend on contract size. So you might consider bundling the VoIP headsets and any other equipment you need with the switch purchase to maximize the size of the deal.

2. Class of service: While modern switches support class-of-service coding, many corporate data networks don't take advantage of the technology. Nicklas describes class-of-service technology as almost a secret key for dealing with the strict latency and packet loss requirements of a true real-time service like VoIP. Basically class-of-service ensures that VoIP packets get priority, so that if the network slows down, other, less time-sensitive packets, such as machine-to-machine transfers and e-mail, are delayed rather than the voice traffic.

"Often you can get away without this," he says, because a switched Ethernet network is hard to overrun. But it does improve quality of service and can be a lifesaver in a denial-of-service attack. It virtually eliminates "jitter," a condition that arises when packets arrive scrambled, with some delayed. This isn't a problem with most applications, which can wait until the packets arrive and the file is rebuilt. Voice can't tolerate these delays.

Tip: Adapt your carrier's service-level coding scheme, Nicklas says. That saves the overhead of recoding packets at the network interfaces.

3. Identify choke points: "VoIP is the canonical real-time application," Nicklas says. "Most voice applications spit out a steady stream of packets." While that may not strain the switched Ethernet network as a whole, it can cause problems at choke points such as T1 connections. So these should be evaluated before switching from analog to digital voice. Also, while class-of-service protects VoIP packets from network slowdowns, other traffic may suffer. Be alert for decreasing quality of service of other applications.

Tip: While analog voice runs at a standard 64Kbit/sec., that same traffic digitized requires 83Kbit/sec. Compression can lower that but also can affect quality and cost because the end-point equipment needs extra intelligence to compress and decompress the signal in real time. The carriers charge more per simultaneous channel for compressed voice service because it requires extra silicon in the switches. "At XO, we support 16 simultaneous uncompressed voice channels per T1," Nicklas says. This allows some bandwidth for TCP traffic during peak loads. So he suggests dividing the peak call load by that number to estimate your T1 requirements.

4. Ensure dependable service: "People have the idea that VoIP is less dependable than POTS [plain old telephone service]," says Nicklas, whose network handles both. "But that is not necessarily true. Class-of-service equipment has been common in carrier-class networks for years now, and it is very dependable. So the technology being sold for on-premise building installation is very solid."

Presuming you have modern network equipment internally, therefore, the most likely causes of service interruptions are external -- for example, damage to the underground cable carrying the service to the building. "If you really need uninterrupted service, you need to do an end-to-end analysis," Nicklas says. "If your service provider is running your POTS and data into your office on the same cable, maintaining emergency POTS lines offers little extra security.

"Many medium-size companies depend on cell phones for emergency communications when their main phone service is out," Nicklas says. Depending on how critical telephone service is to the business, you might want to consider dual cable connections to your carrier and even splitting your voice/data traffic between two carriers.

Tip: Unlike POTS, which powers hard-wired phones through its own network, VoIP handsets are usually powered from a wall socket, which means that if the power goes out, the phones do, too. If this is a problem, and cellular isn't an adequate backup, Nicklas suggests considering power over Ethernet. "This adds to the cost of the network but provides an independent source of power to the handsets."

Overall, he says, moving to VoIP is not as demanding as it might seem. "If you have the opportunity, start small, with a satellite office for instance, to gain experience," he says. "But we have clients who have cut their entire organization over from POTS to VoIP overnight without a ripple."

XO offers a free white paper on VoIP issues.

For more information, read the following articles:

"VoIP converts say good riddance to Centrex"

"VoIP systems increase network support burdens"

"10 steps to VoIP nirvana"

Bert Latamore is a journalist with 10 years' experience in daily newspapers and 25 in the computer industry. He has written for several computer industry and consumer publications. He lives in Linden, Va., with his wife, two parrots and a cat.


Copyright © 2007 IDG Communications, Inc.

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