If you’ve deployed VoIP at any level then it is quite likely that you have received complaints about poor call quality.  How exactly does one measure VoIP call quality and how does one go about troubleshooting the cause of the poor quality?

VoIP Metrics

Maintaining high quality VoIP calls can be difficult as VoIP is more sensitive to network delays and packet loss compared to any other network applications.  VoIP quality is measured based on the following metrics:

  • Network Jitter and Delay - excess jitter and delay result in calls breaking up and can be mitigated by the use of jitter buffers, however, too much jitter buffer can cause unacceptable voice delays
  • Packet Data Loss – packet loss can occur for a variety of reasons including link failure, high congestion levels, misrouted packets, buffer overflows and a number of other factors.  Packet loss can be controlled using packet loss concealment techniques within the playback codec.
  • Latency – measured in milliseconds (ms) results in voice delay and echo
  • Mean Opinion Score (MOS ) – indicates the percieved quality of the call and is expressed as a number in the range of 1 (poor) to 5 (excellent)

Troubleshooting the Old Way

Historically, network or VoIP engineers have used a variety of tools to monitor and measure the call quality components including:

  • Passive network monitoring tools that monitor VoIP performance based on network performance statistics and estimate MOS score
  • Protocol analyzers - hardware or software tools that capture and analyze VoIP traffic packets and calculate jitter, and latency directly from the packet stream.
  • Dedicated VoIP tools - originally developed for the telecomm industry and are great for testing IP phone and gateway designs but not as good at solving deployment problems within the network.

Unfortunately, these tools will not provide a correlation between the specific call detail and the underlying network performance to identify the root cause of the poor quality.  Enter SolarWinds VoIP & Network Quality Manager.

Troubleshooting With SolarWinds VoIP & Network Quality Manager

SolarWinds VoIP & Network Quality Manager is an evolution of our IP SLA Manager and provides VoIP monitoring and troubleshooting alongside WAN performance monitoring.  VoIP & Network Quality Manager works by correlating the call detail record (CDR) with the IP SLA operation that corresponds to the network call path.  With VoIP & Network Quality Manager you can:

  • Get at-a-glance insight into VoIP sites, calls by region, failed calls, and more
  • Monitor site-to-site WAN performance using Cisco IP SLA technology
  • Search and retrieve call detail records by call origination & destination, region, call time, call status, or quality metrics
  • Correlate detailed call metrics with underlying network performance data for faster troubleshooting and root cause analysis


With VoIP & Network Quality Manager, you can troubleshoot poor VoIP calls in three easy steps:

  1. Retrieve the call detail record of the affected call using VoIP & Network Quality Manager’s call search
  2. View the IP SLA performance details for the corresponding call path
  3. Drill down for detailed performance statistics for each router in the call path


SolarWinds VoIP & Network Quality Manager will soon be available for download.  In the meantime, you can learn more here.