Quality Of Services (QOS) Troubleshooting Print

This article covers the following topics:

• Quality of Service issues list
• Most common symptoms and their causes
• Information needed for Technical Support
• VoIP Scout test interpretation
  
  • VoIP Scout user interface
  • Packet Loss
  • Delay
  • Jitter
  • Connectivity Loss

Quality of Service (QoS) issues include:

• one-way audio
• dropped calls
• garbled sound
• static
• echo
• sound delay
• fax failures

The most common Quality of Service issues and the likely causes are described in the table below:

If the information above did not help, contact our Technical Support team. Be prepared to provide the following information:

• exact description of issue;
• affected period of the calls (e.g. whole call, or starting in a middle of a conversation);
• affected phones;
• affected numbers;
• accessories (headsets) usage;
• presence of the issue on handset and speakerphone;
• your working hours and peak hours;
• timeframe when issues occur (e.g. all the time, randomly, during peak hours)
• bandwidth test results (Telecomsvc.com/broadbandtester & speedtest.net)
• your network eqipment information and passwords:
• Internet Service Provider (ISP) & Type.
• Modem(s) make and model.
• Router(s) make and model.
• Switch(es) make and model.
• The number of computers, servers and other devices on the network.
• The latest call examples:
  • exact time,
  • time zone,
  • to number,
  • from number.
    Note: collect examples for the last 24 hours.

Intermedia Technical Support will run a VoIP Scout test using one of the computers on your network. Make sure that PC used for VoIP Scout is not powered off, hybernated, put to sleep or disconnected from the Internet for the whole duration of this test. Once the test is completed, you or your IT can use the following guide to interpret it:

VoIP Scout report measurements, explanation and possible issues are described below:

Packet Loss

Packet loss is the complete loss of data packets as they travel between our network and the VoIP Tester.

Packet Loss causes the following issues:

• Robotic speech.
• Cutting in and out.
• Fax failures.
• In extreme cases, packet loss will be interpreted as a Connectivity Loss.

Packet loss thresholds:

• 0% to 1% Good call quality. Faxes will begin failing.
• 1% to 2% Borderline for Voice.  Sensitive ears will begin to hear robotic sounding speech. Faxing failing.
• 2% or more Abnormal audio.

The screenshot below shows Packet Loss (red bars):

Recommendations:

• Check the network equipment for compatibility.
• Re-configure the network equipment per our instructions if needed.
• Provide your ISP with the test results for investigation.
• In case if spikes in delay occur during your normal business hours ensure that Bandwidth Management is  configured properly.
• Check if you have enough bandwidth and upgrade if needed.
• Move your phones to separate circuit. 

Delay

Delay is the amount of time required for a data packet to travel from one specific point to another. 

Causes the following issues:

• Robotic speech.
• Audio delay / parties will begin to talk over each other.
• Audio cutting in & out.
• Fax failures.

Delay thresholds:

• 0 to 100ms — Excellent call quality & faxing.
• 100 to 200ms — Good call quality & faxing.
• 200 to 250ms — Call quality and faxing starts degrading.
• 250 to 300ms — Callers start noticing audio delay, faxes fail.
• 300 and above— Poor call quality, faxes fail completely.

The screenshot below shows Delay represented in blue lines:

Recommendations:

• In case if spikes in delay occur during your normal business hours ensure that Bandwidth Management is  configured properly. Proritize sensitive VoIP traffic.
• Provide your ISP with the test results.
• Check if you have enough bandwidth and upgrade if needed.
• Move your phones to separate circuit.

Jitter

Jitter occurs when the packet arrival varies from the expected interval.
Jitter is the variation in latency/delay (see above).  When there are spikes in latency, the Intermedia jitter-buffer will try to compensate by expanding the jitter buffer.

Causes the following problems:

• Static or robotic speech.
• Audio delay / parties will begin to talk over each other.
• Fax failures.

Threshold:

• No more than 100ms Jitter.

The screenshot below shows Jitter represented in green lines:

• In case if spikes in jitter occur during your normal business hours ensure that Bandwidth Management is  configured properly. Proritize sensitive VoIP traffic.
• Provide your ISP with the test results.
• Check if you have enough bandwidth and upgrade if needed.
• Move your phones to separate circuit.

Connectivity Loss

Connectivity Loss occurs when packet loss reaches 100%, or in other words, no data is passing either direction between our network and the VoIP Tester.

Causes the following problems:

• Dropped phone calls.
• Fax Failures.
• Loss of registration.
• Inbound call failures.
• Outbound call failures.

No level of unexplainable Connectivity Loss is acceptable in the VoIP Test results.  Explainable connectivity loss would include:

• The computer running the VoIP Tester goes into sleep mode.
• The computer running the VoIP Tester is accidently turned off.
• Power loss in the customer's building.

The screenshot below shows Connectivity Loss (black bars):

No level of unexplainable Connectivity Loss is acceptable in the VoIP Scout results. Explainable connectivity loss would include:

• The computer running the test goes into sleep mode
• The computer running the test is accidently turned off
• Power loss in your building

Provide your ISP with the results of the VoIP Scout test in case of unexplainable Connectivity Loss.