Networking

Is your network ready for VoIP?

Switching to VoIP telephony systems is gaining momentum with consumers and businesses alike. If you are planning to make the leap, make sure your network is ready.

We may tolerate a web page loading slowly, but get irritated when the quality of an Internet telephony conversation is less than pristine. With that in mind, I would like to share a "network admin" experience with you.

A friend of mine uses Skype, a form of Voice over Internet Protocol (VoIP) telephony to talk to her daughter in France. It saves lots of money and the video option is nice. For several months now, everything has been working famously.

Every once in a while they could not understand each other during their Skype call. But, they could chat using the messaging option. So, they would suggest switching to their mobile phones. Doing so upped the cost per call significantly.

What changed

My friend finally called, explaining the problem and how it was sporadic in nature. One time everything was fine. The next, it was impossible to understand each other. They were living with it, but the outages were increasing in frequency. That's not something a concerned mother wants to deal with.

Luckily, I was somewhat prepared for this. Another friend of mine just passed the CCNA Voice. After my heart-felt congratulations, I put him to work, asking about the intermittent Skype problem. His first question: What changed? I felt somewhat smug. That was my first question as well. Trouble is he got the same answer I did: Don't know.

Test the network connection

Based on the random occurrences, he suggested testing both ends of the connection when Skype is working correctly and when it's not. Before I could ask how, he mentioned there are websites that measure network connections for VoIP quality.

Visualware is one such website. It is unique in that their online networking tests do not need to install an associated application on computers being tested. Just connect to one of their servers located around the world:

In my friend's case, she picked Paris and her daughter selected their home town in the United States.

Results

I was not able to get actual test results from my friend. Yet, I wanted to show the wealth of information obtained from the test. Below are test results when I connected to a server in Paris:

Notice the test requires choosing a codec. We used the G.729 codec. It and SILK are the codecs used by Skype.

In my case, jitter and packet loss were acceptable, but that was not the case with the daughter's test results. Both were down in the red zone when the Skype connection was unusable. The next slide depicts the results in graph form, showing jitter and packet loss information for individual packets:

It's somewhat subjective, but the Mean Opinion Score (MOS) is the best way to have a remote user convey their test results. The score range extends from 5 (perfect) to 1 (impossible to communicate). The following slide displays the test connection summary and my MOS score of 4.1:

The daughter's MOS score slid below 1.5 when the conversation was not understandable.

Now what?

The randomness had me puzzled. With mom's permission, I fired off an email to the daughter with some questions. I asked about existing bandwidth, how many were using the same Internet connection, and what it was being used for.

It turns out the apartment is part of a multi-dwelling building. An internal Ethernet network funnels all traffic to the Internet. The biggest clue was several people in her apartment complex play the same Internet game, usually at the same time to compete against each other. Guess when she was having trouble talking to her mother on Skype?

I felt it best to mention that this kind of testing cannot duplicate the exact route VoIP packets take between the two connection points. Meaning there is a chance that the problem may be missed. That said, the tests provided by Visualware are a good starting point due to their simplicity to use.

Final thoughts

If you are considering installing a VoIP telephony system, or are having problems with an existing install, the first step is to check out network performance with tests like those provided by Visualware. I also recommend reading this white paper. It explains the importance of testing for connection quality as well as connection bandwidth.

To get an idea how pervasive VoIP telephony will become, check out this link. It explains how Cisco upgraded an orbiting satellite and made the first VoIP call without the help of any terrestrial infrastructure.

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Information is my field...Writing is my passion...Coupling the two is my mission.

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