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Network pros troubleshoot VoIP quality, reliability

As the telephone itself disappears from the voice communication process, engineering VoIP quality becomes more critical. Network managers assess what they're hearing now.

This article can also be found in the Premium Editorial Download: Network Evolution: Networking development takes on voice quality, SD-WAN security:

Not long ago, Eric Prosser's nephew asked him about a peculiar piece of technology: the rotary phone, the one with the numbers positioned in a circular layout and "dialed" using a finger to rotate each digit to a fixed-stop position.

With cellphones now ubiquitous -- and the only technology that a growing segment of the workforce has ever known -- even older workers familiar with landlines and corporate private branch exchanges (PBXs) have come around to the idea that a dropped call is normal. And that, Prosser said, has helped smooth the adoption of voice over IP (VoIP).

"Nobody thinks twice about [a dropped call] because their cellphone does it all the time," said Prosser, IT officer for Santa Clara County Central Fire Protection District. "The entire [VoIP] market has matured to where I think the quality is there; it's just a matter of how you design your system." Prosser has switched to VoIP for all calls at the department's 15 fire stations.

How you design your system establishes the VoIP quality you need. The old national Bell telephone system set a high bar for engineering its network so customers could make phone calls that didn't have static, fade in and out, or drop completely. The traditional five-nines standard meant near-constant network uptime, with a mandated maximum of 5.26 minutes of downtime annually. Then came the internet, which gave rise to VoIP, collaboration and video -- applications that depend on high-quality, low-latency connections. While it hasn't performed quite to 20th century standards, most users have found VoIP quality supports their needs.

But as more business is conducted over applications, near-constant uptime and high quality become critical. Companies are reducing UC operating costs by investing in voice quality platforms, according to Irwin Lazar, vice president and service director at Nemertes Research.

"For those engaging with customers, prospects, etc., there is still an expectation of high-quality voice," Lazar said. "There's a lot of interest in figuring out how to maintain voice quality as voice interfaces shift into apps, [like] making calls from within Salesforce, onto mobile devices and into websites."

Simple VoIP features matter to users

Laurie French, director of technology operations at The PGA of America, has cut communications costs by 25% by replacing the PBX phone system with UC services. The golfing organization has implemented unified communications as a service (UCaaS) from RingCentral.

"If you ask anyone in our organization what the coolest thing is, they'll say it's the ability to get voicemail sent to email," French said. "They can configure it so they can put one phone number on their business card, and someone won't know if it's their cellphone or desk phone."

Problems with voice quality are rare, she said, but when they do occur, it's difficult to isolate the cause. Since the PGA has only one network engineer, the organization decided to install a separate circuit fully dedicated to a RingCentral platform. Still, it can be difficult to pin down the source of poor voice quality, especially when mobile phone use is added to the equation.

The entire [VoIP] market has matured to where I think the quality is there; it's just a matter of how you design your system.
Eric ProsserIT officer, Santa Clara County Central Fire Protection District

"With the use of cellphones today, quite often if you have a call quality issue like static or delay, there are so many actors between that cellphone and the call that are outside everybody in the process," French said.

The convenience of VoIP also is a big plus for Private Jets, an air charter company based in Oklahoma. It uses cloud communications services, including VoIP, from Vonage Business.

"The best part of the whole thing is we don't have to be at the office; we don't have to be at our desk to get our calls," said Candy Lovin, charter operations manager for Private Jets. Never missing a call is especially important, since a large part of the company's business is transporting organs for transplant. But that peace of mind only costs Lovin a couple hundred dollars a month for as many extensions and users as she wants.

Monitoring network performance

Clearly, there is a need for monitoring not just video and VoIP quality, but the network traffic and performance of the myriad UC services and applications so every employee, whether at headquarters, on the road or working from home, has a reliable experience.

Don't rely on the monitoring tools that are built into enterprise applications, Frost & Sullivan wrote in a recent white paper on monitoring unified communications and collaboration networks, pointing out that that those tools may miss data, overlook poor performance or ignore key information. 

"Instead, IT managers should deploy a full suite of network monitoring and management solutions that can deliver robust, complete reports -- and the analysis to enable proactive and reactive responses in real time," the consultancy wrote.

Troubleshooting VoIP quality

The network is probably the most significant factor affecting voice quality, but it's not the only factor, said Rafael Benitez, a research director for Gartner. When companies have problems with the quality of their VoIP service, he suggested a variety of starting points for troubleshooting:

  1. Confirm your data service is suited for real-time services. There could be insufficient capacity on the WAN.
  2. Change the codec configuration of a phone from the default G.711, which is not the best algorithm to handle imperfect network conditions, to something more resilient, such as G.722.2 or VP8. Some phones may also support forward error correction or have other features to improve quality by consuming less bandwidth, including silence suppression.
  3. Decrease the size of the voice payload. The issue might not be bandwidth; it might be packet loss. One way to overcome it is to make the payload size smaller, if the phone supports it, and reduce packet size by half -- for example, from the typical 20 milliseconds to 10 milliseconds. The drawback is that handling twice as many packets increases the amount of bandwidth required for a call.

In trying to sort out and troubleshoot voice quality issues, it's possible that the network may not be at fault. For users with a VoIP or video client on a laptop, poor quality could be a case of resources with another CPU-bound program, for example. But chances are it's the network.

"Often, voice quality issues are network-related or the way solution elements -- gateways, phones, media servers -- have been configured in a less than optimal way that won't deal well [with problems]," Benitez said.

Interface errors can be another source of poor voice quality, according to Terry Slattery, principal architect at NetCraftsmen, who writes about VoIP quality issues in his blog. Interface errors can be caused by poor cabling, cables that run next to magnetic sources, or radio frequency (RF) noise or power loss in fiber optic cables.

One cause of packet loss to look for is network congestion at speed mismatch points and aggregation points of multiple high-speed data flows, Slattery added. In the end, though, it all starts with the network handling the calls.

"The network design will make or break you," said Prosser, who separates voice and data traffic on multiple virtual LANs (VLANs) at his Santa Clara County fire stations.

Although Prosser chose RingCentral to provide UCaaS, his advice for others who control their infrastructure is not to rely on vendors to make sure everything's running smoothly.

"RingCentral is good at helping you determine how your network is designed and for security, but they're not the people behind the scenes chunking away at the keyboard," Prosser said.

Prioritizing traffic is key

One interesting development for VoIP quality and other time-sensitive UC services is the potential of the software-defined wide area network (SD-WAN). "There's a lot of anticipation and hope that SD-WAN technology will allow real-time services like voice and video to run over cheap transport and network access," Gartner's Benitez said. "That's one area that is getting considerable attention in the last year or so."

He estimated that reducing the amount of required MPLS service and supplementing it with dedicated internet or broadband could lead to a potential WAN cost savings of as much as 20%, without sacrificing much voice quality. 

Of course, that will still require quality of service to prioritize the most important traffic. Slattery said he was once asked to diagnose connection problems at a billing office fed by a T3 link (40 Mbps) and found that streaming video and music from Pandora and other sites was hogging half of all the available bandwidth.

"We prioritized voice and business traffic over entertainment traffic," Slattery said. "Then what we heard was, 'The internet seems sluggish, but the applications are running great, and there's no problem with voice calls.'"

You can't make everyone happy, so his general advice for network engineers is to keep it simple.

"If you have a truly unique network, you probably have truly unique problems. That's probably not where you want to be operating an IP network. You want to use common practices on how to design and operate IP networks," Slattery said. "You'd like the problems to be already known and understand how to diagnose those problems and correct them."

Next Steps

The business case for VoIP

Tips for robust VoIP infrastructure

How enterprises are enhancing VoIP

This was last published in June 2017

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