Your Internet Connection and VoIP

One of the biggest factors that can affect the experience of using VoIP is the internet connection. VoIP does stand for Voice over Internet Protocol, after all. The main misconception is that as long as you have a fast internet connection, VoIP should work. While bandwidth does play a large factor, there are also other things to take into consideration. We will take a look at the MOS, or Mean Opinion Sore, to help you get a better idea of how suited your connection is for VoIP.

How Your Internet Connection Affects Your VoIP Experience

There are other factors that can affect your VoIP experience such as the audio codec used during a call, latency, jitter, packet loss and packet order. Bandwidth usage and internet connection requirements for VoIP primarily depend on the codec used during the call. The two most common codecs used are G.711 (ulaw and alaw) and G.729. G.729 requires less bandwidth due to its higher compression rate, while G.711 uses less data compression for better audio quality but requires more bandwidth. As your audio is sent audio through a series of sequential data packets, both codecs can experience audio quality issues if the packets get delayed, corrupted, lost or received out of order.

Two Common SIP Codecs and Their Bandwidth Requirements:

Codec

To Internet (Up) From Internet (Down)

G.711

80 Kbps 80 Kbps

G.729

16 Kbps 16 Kbps

Common Types of Connections

DSL

Slowest and, generally, not much of an improvement compared to Dial-up

Mobile Data

Speeds vary widely, from slower 2G/Edge to faster 4G and LTE networks. Lots of restrictions on usage allowed by carriers (cellular providers)

Cable

Some latency and possible congestion during peak hours. Otherwise good choice for speed and stability

Fiber Optic

Higher bandwidth and less susceptible to congestion

Satellite

Slow upload speed, high latency and highly affected by weather conditions. Generally the worst choice for VoIP

Testing Your Connection

The best way to see how well your experience with VoIP will be on your current internet connection, is to find your MOS (Mean Opinion Score) score. A MOS score of 4.5 is Very Good, with 4.0 being Good, 3.0 being Fair and 2.0 being Poor.

There are ways to find out how well your internet connection can handle VoIP/SIP communications. We typically use the following three tests:

  1. Test your ping to our servers
  2. Test your connection for general quality for VoIP (When replying to trouble tickets, please provide the URL that you are given at the end of the test specifically under the “Summary” section of the test).
  3. Test your overall bandwidth

*** Please select the server closest to New York, NY — this will provide us with real world results as our servers are located in New York, NY.

MOS is More Important than SPEED (a.k.a. Bandwidth)

As we mentioned, having a lot of bandwidth (which most people equate to SPEED) does not automatically mean you will get good results using VoIP. Below illustrates how MOS trumps bandwidth with regards to VoIP. As you can see, among the 3 internet connection results, the internet connection with the highest downstream bandwidth actually scored the lowest MOS score of 3.7.

While 3.7 is not completely bad, it does show that there are other factors that do your VoIP experience. The follow graph show the same 3 internet connections and the factors that can affect your VoIP experience. You’ll notice the correlation between MOS and the different test results — notably, the Downstream packet loss affected the MOS the most.


Jitter, Packet Loss, Packet Discards and Packet Order are all used to define Quality of service in network connections.

Quality of Service Terminology

Jitter

Packets from the source will reach the destination with different delays, possibly resulting in stuttering audio.

Packet Loss

Some packets may fail to be delivered if their payload/data is corrupted or they arrive when their buffers are already full.

Packet Order

When a collection of related packets is routed through a network, different packets may take different routes, each resulting in a different delay. The result is that the packets arrive in a different order than they were sent. When reconstructing the audio information on particularly poor connections some audio may be delayed or sound out of place.

Conclusion

At the end of the day, both the stability of the connection and available bandwidth can affect your experience with VoIP. While you can work around some lower bandwidth situations (by using a higher compression codec like G.729), jitter and packet loss are harder to get around. There are also other factors that we did not cover, as it is beyond the scope of this article.
Knowing this, you will have more control over your experience with VoIP.

“Knowing is half the battle.”

— Famous Character