Troubleshooting VoIP quality problems

The most common tech support call, the one that every tech dreads, and makes every customer want to throw their phone out the window, is the elusive “Poor call quality.”

The problem with most call quality issues is that they are easy to diagnose, but depending on the issue, difficult to fix for most customers.

I’ll list the most common causes of call quality issues I saw during 4 years of managing a VoIP carrier, and give my advice on how to easily fix them.

The biggest offender: Jitter

Jitter shows up as choppy audio, or sometimes garbled words. The problem is that VoIP voice traffic is sent over UDP which is connectionless. A VoIP call is chopped up into packets to be sent across the network. Because each packet can take a different route or path to get from the carrier’s switch to the customer’s phone they can take slightly different amounts of time to get from point A to point B. This causes the packets to arrive in a different order, resulting in a call with choppy or scrambled audio. We call this Jitter. Jitter is actually defined as the variability over time of the network latency, and it sucks on most small business internet connections.

The Fix: Use Jitter Buffers

Most VoIP devices support using a jitter buffer, which will store all of the packets in a queue once they’ve arrived and make sure they all get put back in the proper order. Depending on the size of the jitter buffer you can get a small delay in the call, but it’s usually a fraction of a second or less, which isn’t even noticeable to the human ear.

2. Latency

Latency is the amount of time it takes for the voice data to get from the caller to the callee. Latency is caused by a few things: Propagation, Handling, and Queuing.

Propagation is just physics at work. The electrons carrying your voice have to travel through copper wires and fiber. Electrons travel through wire at about 125K miles per second. If you figure your call has to travel from your phone, through your ISP’s infrastructure, over fiber to your ITSP, through their network to the caller’s carrier, and then do the whole thing in reverse, it’s not uncommon to have a delay up to 70 milliseconds. This doesn’t seem like much, and your ear would never be able to detect this small of a delay, but once you add handling and queuing delays it starts to add up.

Handling delays is caused by the equipment that forwards your packets around, such as routers and switches. Every time a router has to decide where to send your packet next, there’s a tiny delay. Again, these can add up.

Finally, Queuing is a result of network congestion. When a network interface somewhere in the path of your call gets congested it causes a small packet traffic jam. Normally you would never notice this while browsing the web, or downloading a file, but in real time communications like a phone call, there’s no “buffering” like when you start a YouTube video. So you instantly feel this delay.

The Fix: Prioritize

High end Internet service can prioritize VoIP traffic which give you lower latency and more predictable jitter on your ISP’s side, and a investing in a quality VoIP router can fix these problems on your side. Unfortunately it’s hard to get an Internet connection which features Policy based network management, QoS (Quality of Service), CoS (Class of Service) or MPLS (Multi-Protocol Label Switching) for less than $250/month.

3. Poor Internet Connection

Similar to above. Most Internet service is designed for web browsing and download speeds, which they can optimize using some of the tricks mentioned above like Queuing and bursting which can cause Jitter.

The Fix: Business Class High Speed

Most Providers will offer a “Business Class” service, but many providers unfortunately just charge more and offer the same residential service for a higher “business” price.

4. Inadequate Router

Unfortunately, Bad equipment is bad equipment. That great $30 Linksys you got on eBay probably can’t cut it.

The Fix: Install a VoIP Router

The problem stems from the fact that most companies use the same Internet connection for both VoIP and data. You can do this without a problem as long as your router prioritizes the VoIP traffic. If you don’t your call quality is going to tank everytime your other network users downloads a large file for example. A good router will prevent this by prioritizing your VoIP traffic. Depending on your network you can get a good VoIP router for $350.

5. Internal Network Improperly Configured

Commercial VoIP is still young. If you haven’t designed your internal network to handle the high demands of VoIP traffic and especially if you share your network between VoIP and data, you can expect quality issues to pop-up.

The Fix: Network Configuration

Get a VoIP router, try to operate a dedicated Voice network if possible, and make sure all of your network cabling is up to snuff.

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