In this multiple part series, I’m exploring the four evils that are the curse of high-quality Virtual PBX: Bandwidth, jitter, packet loss and latency. Today’s subject is jitter.
What is Jitter?
Jitter is a little bit hard to explain. Remember when we talked about how latency is the measure of packet delays over a VoIP network? Jitter is just the variation in the time between packets arriving. In other words, it’s the variation in latency.
Each IP packet comes with a sequence number and time stamp in its header. This is how the VoIP equipment knows in what order they need to be re-assembled and when they were produced. A connection is experiencing jitter if many of the packets come in at varying differences between packet time stamps.
When this happens you get conversation problems like you can hear in this audio example.
Causes of Jitter on a VoIP Network
Jitter is caused by congestion, defective equipment, and poor data service providers. In general, higher levels of jitter are most likely to occur on either slow or heavily congested data circuits.
How to Decrease Jitter on Your VoIP Network
First, you need to find the source of the excessive jitter. This can be accomplished by a competent local IT vendor or in-house IT administrator.
If you don’t have that luxury, two things you can do that will decrease jitter right away are to update your router and/or increase the bandwidth on your WAN
Updating Your Router to Reduce Jitter
Most new routers have something called a jitter buffer. Jitter buffers are shared data areas where voice packets can be collected, stored, and sent to the voice processor in evenly spaced intervals. This reduces the impact of jitter and improves the quality of phone calls. The buffer can be either hardware or software-based. A jitter buffer works to control the effects of jitter on circuits that have small to medium amounts of jitter.
Most quality routers have jitter buffers these days, but that wasn’t always the case. Make sure that you have a modern router and that it can handle the amount of bandwidth delivered by your Internet service provider.
Increase WAN Bandwidth to Reduce Jitter
Wide area networks (WAN) is the term given to the connection between your office building and your internet service provider. It’s your internet connection and it can be a source of bandwidth congestion. A typical small business Internet connection ranges from 1 Mbps to 10 Mbps.
Your San Francisco-based Internet service provider can provide utilization statistics on your data circuit. If the utilization exceeds 80%, then you have too little bandwidth to support quality voice transmission. If this is the case, you’ll have to increase the size of your data circuit.
If the circuit appears to have the necessary bandwidth, but you are still experiencing excessive jitter, it is your Internet provider who is the culprit. You need to move to a data carrier that has the proper bandwidth to maintain acceptable VoIP quality.
Excessive jitter causes problems with VoIP, no doubt. But these days, it’s happening less as Internet speeds continue to improve. Working with quality providers and making sure that your data hardware is current and of sufficient capacity to handle your traffic will reduce jitter to an acceptable level for VoIP.