Dodging VOIP Predeployment Pitfalls

By Paula Musich  |  Posted 2005-12-12

Dodging VOIP Predeployment Pitfalls

Adding voice onto an existing IP network is not the same as adding any other data application. Successful VOIP rollouts require careful planning, proper design and—in most cases—changes to the networking infrastructure to adequately support latency-sensitive voice traffic.

But the first and most critical step that enterprises can take to ensure a successful voice-over-IP installation is a predeployment assessment of the network that will carry the voice traffic.

Fully 85 percent of existing networks cant handle VOIP traffic, and 75 percent of enterprises that dont analyze their IP network infrastructure before deployment wont see a successful VOIP implementation, according to Gartner Inc., of Stamford, Conn.

Click here to read about why some VOIP operators arent dialing in to 911.

To handle the increased demands that voice places on data networks, "90 percent of networks in North America today will require additional build-out to support voice, and 100 percent of them will require some configuration changes," said Gartner analyst Jeff Snyder.

Beyond the obvious changes required—such as upgrading slow LAN or WAN links, and adding POE (power over Ethernet) to network switches—there is a host of network problems that often are not seen by data applications or are tolerated because of their infrequency. No matter how good network engineers believe the network is, such problems can derail a VOIP implementation.

"IP networks by design are just good enough," said Loki Jorgenson, chief scientist at Apparent Networks Inc., a Vancouver, British Columbia, company that supplies VARs and systems integrators with a tool that can find such problems. "Things that have been a nuisance for network engineers are critical tripping points for voice. Networks are riddled with potential degradations that are often hard to find but easy to resolve. So you have to start out with the assumption that your network is dirty, and you have to bring it up to an acceptable level for voice."

Jorgenson said he believes there is "an ecology of Layer 1, 2 and 3 defects" that can derail VOIP deployments. A predeployment assessment using tools such as Apparent Networks AppareNet Voice can uncover NIC (network interface card) driver issues such as full- and half-duplex conflicts.

When ISPs implement rate-limiting queues that throttle predefined traffic groups when bandwidth is in contention in their Cisco Systems Inc. routers, packets can be lost, and voice quality suffers, according to Jorgenson.

In addition, there is always latency that can be caused by myriad contributors.

"Satellites introduce 250 milliseconds of delay," Jorgenson said. "Voice should always be below 150 milliseconds. Devices being added in the path can push you over a threshold. I dont think theres a lot of awareness of latency at this level, and that makes it hard to make good design choices."

Then there are media errors that can be caused by "anything from cabling to bad optic ends, electromagnetic interference, wireless random loss or corruption," Jorgenson said. "Media errors are extremely difficult to detect and resolve, and they will show up as jitter variation and loss and have no impact on any other application except voice."

Using the AppareNet Voice tool, engineers at managed services provider IPC Technologies Inc., in Richmond, Va., start their predeployment assessments by testing a customers WAN links.

"Youll see call-quality issues there first," said Kurt Wright, senior network engineer at IPC. Engineers execute tests that measure bandwidth utilization, packet loss, round-trip time, latency and packet reordering. They also look at mean Opinion scores, which measure call quality.

Next Page: Asking the right questions to prevent disaster.


The speed of frame relay links was a concern for premium movie channel provider Starz Entertainment Group LLC when it was planning a VOIP rollout. "We were going to try to do a VOIP rollout with a WAN infrastructure not quite big enough," said Gary Pfeiffer, vice president of IT for Starz, in Englewood, Colo.

Beyond detecting such issues, a predeployment assessment establishes a base line for existing calling patterns to help in guiding the design of a VOIP system, according to IPCs Wright, whose company resells ShoreTel VOIP equipment.

One surprise that emerged from such an assessment at Starz was the discovery of much unnecessary traffic on the network, according to Pfeiffer.

Network providers are fighting the FCC on VOIP wiretapping Click here to read more.

For small and midsize enterprises, a predeployment assessment can transcend just looking at whether the network can carry voice calls.

"What people are not thinking about are issues like, Do you have any change management processes in place? Do you have uninterruptible power supplies in your phone closets? Do you [track problems in] a trouble report?" said Grant Vogelsang, senior customer systems analyst at SaskTel, in Regina, Saskatchewan.

SaskTel, in its full network assessments, looks at environmental elements that can affect a VOIP deployment.

"We look at all their [wiring] closets, cabling structure, patch panels. Most people dont even know what is hanging off which port," Vogelsang said. "People talk about five nines [reliability] but dont know whats required for it in terms of organizational structure."

Beyond solving the kinds of problems that such assessments turn up, another critical success factor for VOIP implementations is the use of QOS (quality of service) prioritization to ensure that latency-sensitive voice traffic gets priority when applications contend for limited bandwidth.

Some resellers might be tempted to take a shortcut to QOS by recommending a boost in performance, believing that contention wont take place on a fast LAN.

"When [bandwidth contention] does happen—and it always does—the users network isnt provisioned to prioritize voice over data," said Gregg Jankowski, IP communications practice manager at Cisco reseller Analysts International Corp., in Auburn Hills, Mich. "From a resellers perspective, its a shortcut that can be taken that saves on engineering services hours and makes it a [more] profitable deal."

Jankowski said he believes its critical to ensure that QOS provisioning is consistent between the customers network and the carriers implementation of QOS, which is called Multiprotocol Label Switching, or MPLS.

"The critical component is making MPLS work properly between the customers distributed facilities. People dont thoroughly investigate and work with carriers to make sure QOS stays consistent and true throughout the WAN," Jankowski said.

Within the customers own network, a preassessment can also look for QOS capabilities within switches and routers and ensure that those functions are "turned on in every component on the network," said Richard McLeod, director of IP communication solutions for worldwide channels at Cisco, in Atlanta.

Predeployment assessments can go a long way toward ensuring the success of a VOIP implementation, but its also important to continue to monitor the network to ensure that it stays up to par. Because change is constant in a network, performance problems can be introduced without detection until users start complaining about call quality.

"The key is that network assessment is not a one-time thing," McLeod said. "Ongoing checking and monitoring the health of the network is an important value add the VAR always brings to the customer."

Check out eWEEK.coms for the latest news, views and analysis on voice over IP and telephony.

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