Secrets of Successful VoIP

Don't stutter, jitter or drop
It Takes a Network to Raise a Conversation.

If you're out to impress larger business customers or affluent consumers with your communications, the last thing you want are dropped calls, stutters, echoes and garbled conversations. (Actually, you don't want this with any calls--customers or family or friends.) These annoyances can be tolerated up to a point on a cell phone but the standard for your office is much higher.

You may have heard IP phones criticized for inconsistent performance and, justified or not, the technology has received a few black eyes. But how much of the problem can be attributed to the corporate data network (and its component devices, the bandwidth provider (DSL, cable), the telephony access provider (ITSP) or even the particular VoIP phone?

You know the drill. Bring in a trusted consultant or VAR to help you with plans and choices. Avoid unnecessary points of failure and the "throwing the whole mess out of the window" syndrome. A knowledgeable network professional is like a good auto mechanic. You keep a phone number handy.

Still, it doesn't hurt to know a little about what you're discussing. You feel more in control if you'll at least educate yourself on the right questions to ask.

A Gentle Education

During a VoIP call, speech is captured as analog information by a phone, then converted into digital information, compressed, and divided into packets for transmission. The whole process is relatively fast, easy and reliable.

Checklist for successful IP PBX implementation

LAN engineered to limit latency to below 200ms
Protocol that recognizes and prioritizes voice packets
Full duplex, non-blocking switches
Business grade routers, cable and related hardware
Voice-capable modems without firewall
Quality IP or analog phones
Business class DSL (upgrade to ISDN or E1/T1 if possible)
Internet service connected to a private backbone
Quality IP PBX hardware (see Epygi Quadro)

If any problems happen, they'll happen at the receiving end where the packets must be reassembled real time, in the correct order, without errors. Even minor glitches in transmission will cause a VoIP call to "break up" like the reception from a distant radio station.

Engineers will say the audio stream "stutters." The people on the call will tell y.., it s..nds ..ke gibberish. Worst case, the transmission becomes so overwhelmed by problems that the connection simply fails.

Properly engineered, VoIP is equal to or better than toll-quality voice. In fact, if bandwidth and system costs weren't an issue, everybody would be enjoying phone calls with CD quality audio. Rather, the best you can do is fine tune your network and subscribe to quality services to ensure minimal disruption.

Is your corporate network voice ready?

The LANs and Internet connections (WANs) used by most small businesses aren't quite ready to handle VoIP. The basic firewalls commonly used for security and virus protection can and do break up VoIP calls.

The low cost routers from the local computer store don’t typically have the horsepower to drive quality VoIP calls. LANs can also become congested, especially when users are transferring large files across the internal network.

Even the best designed network will, from time to time, experience glitches and outages. The goal should be to minimize such problems and, to the extent that the project's budget allows, provide a solid and reliable VoIP experience. IP voice killers are latency, jitter and packet loss.

Are your Internet service providers voice ready?

Your VoIP network includes not only your internal network, or LAN but also your wide area network, the WAN. Your WAN begins with your broadband modem and ends with your broadband Internet provider.

Most people don’t understand that just having a broadband connection is not enough. You actually need a high quality connection to deliver the call fineness you need to run a business.

A lot of smaller businesses connect to the Internet via DSL or cable, most often with inexpensive modems. While such connections work fine for web browsing and email, they are not designed to handle VoIP transmissions. Much less the combination of voice and data.

Likewise, many of the WANs now in use by ISPs were built before the advent of IP telephony. They weren’t originally designed to meet the demanding requirements of error-free, reliable VoIP transmission.

In fact, most of them actually run on a business model designed for oversubscription, which results in frequent latency and jitter. Even the ISPs that aren’t oversubscribed often haven't yet deployed true quality-of-service (QoS) technology to ensure that voice packets get priority over data packets across their networks.

As if ensuring you have a great LAN and WAN weren't enough, you also have to choose a high quality VoIP provider (VoIP Service Provider (VSP) or (Internet Telephony Service Provider) ITSP).

Much like LD providers, which deliver long distance services over the PSTN, VSPs provide you with VoIP calling over the Internet. Like ISPs, not all ITSPs are created equal in terms of network strength, proximity to the PSTN backbone and, of course, good old fashioned customer service.

Regardless of the service provider you ultimately select, you may decide to specify a service level agreement (SLA) that guarantees basic performance benchmarks, usually in exchange for a commitment to spend a fixed amount with the provider over a time period.

VoIP service SLAs tend to be judged on their Mean Opinion Scores (MOS). They can include such factors as call completion rates and the length of time required for a user to hear a dial tone or to connect to the dialed party. Various measurement techniques are used in association with SLAs, including active network tests made at regular time intervals as well as passive measurements that are based on actual calls placed across network.

The bottom line

At the absolute minimum, you must upgrade your broadband connection to ensure sufficient bandwidth for voice traffic from your premises to the Internet.

A typical VoIP call will use about 64KB of upstream and downstream. You should factor in at least 90KB for your first call due to what's called "IP overhead." Assuming peak concurrent line usage, the math looks like this: If your peak usage will be 5 concurrent calls, then you add 90KB + (4 x 64KB) = 346KB.

Be sure to remember that this is 346KB up and down. Most broadband providers will give you much more downstream than they will upstream. Clarify this up front.

If you can't afford a T1, at a minimum spring for a "business-grade" DSL. Anything less and you and yours are in for a big disappointment.

Two last things

First, ensure that your ITSP has a local public switched telephone network (PSTN) media gateway in your area. This will shorten the path your VoIP calls have to take over the Internet before they are converted to travel across the PSTN.

Second, try to use the same broadband provider at your main office and all remote offices. VoIP performance improves when calls travel over a single provider’s backbone vs. having to "hop" across multiple backbones.

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