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Troubleshooting VoIP Problems: Packet Delay

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There are a number of issues arising from network connections that affect the VoIP user experience. Of these, packet delay has the most perceptible effect on user experience. Delays result in high latency – defined as the amount of time a packet takes to reach its destination – which then causes echo and/ or feedback. Voice call quality is affected..

Delay is not really a new thing – it is not even uniquely VoIP. Wire line telephony experiences delays, usually caused by satellite connections. In the case of VoIP, there are several kinds of delays to consider.

Types of Packet Delays in VoIP
When delay is caused within the IP Network, the voice packet is stalled during transmission or queuing. In small milliseconds, this sort of delay is natural. A packet has to travel through different VoIP hardware, routers and switches. Delay may also be compounded by network congestion at the time of transmission, as well as the type of network used. Slower connections, such as through cable modems and DSL, will likely experience greater delay. IP Network delays can then go from less than ten milliseconds to a thousand milliseconds.

End System Delays, on the other hand, refer to delays caused during voice data handling. Packets necessarily go through encoding, jitter buffer, decoding and other processes within the VoIP service. The milliseconds added here largely depend on the jitter buffer size. Decoding delay is negligible. Encoding delay takes about 30 milliseconds or shorter. The jitter buffer size adds the most, and is affected by IP Network delays. The longer the IP network delay, the bigger the buffer size since the jitter buffer is supposed to remove delay variations that affect voice quality. Buffer size can grow to hundreds of milliseconds.

External delays refer to anything outside the VoIP system, and are beyond the control of the user and the service provider.

Effects of Delay on the VoIP User Experience
Regardless of the source of delays, the VoIP user experience is affected. Voice call quality is reduced, and may suffer echo and conversation problems.

Foremost here is how delays affect conversations. If the conversation is one-way, or only one side of the connection is sending out voice packets, the interaction problems may not be apparent. However, in the more likely scenario where two (or multiple) ends of the interaction engage in the conversation, delays can become apparent as speech pauses and interruptions or doubletalk.

VoIP users may also experience conversation echoes. With little delay, echoes can be unperceivable. With larger delays, however, this can be an irritation.

Needless to say, delays can make or break VoIP service providers. It can turn users off or the least encourage them to make the switch to another VoIP provider.

Troubleshooting Packet Delays
Troubleshooting packet delays can mean different things, depending on which side you’re on.

For network administrators and IT professionals, troubleshooting packet delays means getting to the root of the problem. A way to do this is through services like VoIP Spear, which analyse jitter, latency, packet delays, among other factors, at specified end points (origination and destination points) during given intervals. Once problem areas are identified, action can be taken.

Home and business VoIP users can also use VoIP Spear’s services to determine the root of the packet delay. If the problem is at their end, they can:
1. Cut down the systems that packets travel through. If the user connects via Wi-Fi, they need to turn this off and connect directly to the router or switch. This should minimize interference.
2. Check adapters and cables for damage. Damaged hardware can cause delays.
3. If the user is already directly connected to the router, it may help to switch this off first, and turn it back on after a few seconds. Sometimes, a power cycle is all that’s needed.
4. Close all other applications that eat up bandwidth. Dedicate bandwidth to VoIP. If you can, access your router’s software and adjust QoS by assigning voice the highest priority. Current router models allow this.
5. As a general rule of thumb the latency measured in milliseconds to the closest VoIP server shall be under 150 ms in order to maintain a good quality VoIP conversation.

About VoIP Spear
VoIP Spear started in 2009. It is based in SK, Canada, and maintains testing servers all over North America.

About Matt Larson
Matt is a tech blogger, currently associated with VoIP Spear. He is based in the US, and enjoys diving in his free time.

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