The pictures show hub-and spoke (left) or full-mesh (right) generation of VoIP media streams over UDP, using a selected voice codec, for measuring voice quality.

Client Test Agents can be placed behind NAT, since traffic will be initiated from the clients to the server.

By running a VoIP UDP test, you will be able to measure how your network influences the quality of VoIP traffic. An objective quality score on the MOS (Mean Opinion Score) scale is calculated for VoIP based mainly on network jitter and packet loss.

When you start a VoIP test, the Test Agents will generate UDP traffic with a fixed rate and packet loss, matching the codec you have selected. For example, for G.711 the frame size is 218 bytes, and the bitrate is 87.2 kbit/s.

No SIP or H.323 signaling is included.


To run VoIP UDP measurements you need to have at least two Netrounds Test Agents installed. If you haven't already done the installation, consult our quick start guides for various types of Test Agents in the section Netrounds Test Agents.

Then create a new VoIP UDP test or monitoring and fill in the mandatory parameters below: 


Tests only

  • Duration (seconds): The duration of this test step in seconds. Min: 30 s. Max: 604800 s. Default: 60 s.
  • Fail threshold (seconds): The maximum number of errored seconds (ES) that may occur without triggering a fail for this test step. Default: 0.
  • Wait for ready: Time to wait before starting the test. The purpose of inserting a wait is to allow all Test Agents time to come online and acquire good time sync. Min: 1 min. Max: 24 hours. Default: "Don't wait", i.e. zero wait time.


  • Setup type: Select how to set up the measurement: "Client-Server" or "Full-Mesh". The default is Client-Server.
  • Server: A Test Agent that is going to act as the server side. If a NAT router or firewall is present, the server must be located on the outer (public) side.
  • Clients: Test Agents that should participate in the VoIP measurement and exchange VoIP-like traffic with the server Test Agent. 
  • Number of streams: The number of VoIP streams. The streams will use different UDP ports on the client but the same port on the server side. Min: 1. Max: 20. Default: 1. Note: Even if multiple streams are used, a single set of statistics is shown with the worst value picked for each parameter: min (rate), max (loss), max (misorders), min (minimum delay), average (average delay), max (maximum delay), max (jitter), min (MOS), and max (ES).
  • Codec: The following codecs are supported.
    • G.711: Frame size 218 bytes, bit rate 87.2 kbit/s (default)
    • G.729: Frame size 78 bytes, bit rate 31.2 kbit/s
    • G.723: Frame size 82 bytes, bit rate 21.9 kbit/s
    • GSM EFR: Frame size 89 bytes, bit rate 35.6 kbit/s
  • Port: UDP destination port for the VoIP streams. Range: 1 ... 65535. Default: 5000.

Thresholds for errored seconds (ES)

  • MOS: Mean Opinion Score threshold for triggering an errored second. The MOS scale is defined as follows: 5 = Excellent, 4 = Good, 3 = Fair, 2 = Poor, 1 = Bad. Range: 1 ... 5. Default: 4.


  • Up/Down DSCP/IPP: The Differentiated Services Code Point (DSCP) or IP Precedence to be used in IP packet headers. The available choices are listed in the drop-down box. Default: "0/ IPP 0". Note: Test Agents Lite currently do not support DSCP settings in outgoing IP packets.
  • Up/Down VLAN priority (PCP): The Priority Code Point to be used in the VLAN header. Range: 0 ... 7. Default: 0. Note: Test Agents Lite currently do not support DSCP settings in outgoing IP packets.
  • Delayed start (s): (Tests only) Time by which to delay the start of the test within a test step. Default: 0 s.

SLA thresholds (monitorings only)

  • SLA Good: Threshold for good fulfillment of service level agreement. Default: 99.95%.
  • SLA Acceptable: Threshold for acceptable fulfillment of service level agreement. Default: 99.5%.

Result metrics

  • Rate (Mbit/s): Ethernet rate of the VoIP UDP stream. 
  • Loss (%): Packet loss measured.
  • Misordered (packets):  Number of misordered VoIP UDP frames.
  • Delay min (ms): Minimum one-way delay measured.
  • Delay average (ms): Average one-way delay.
  • Delay max (ms): Maximum one-way delay.
  • Jitter (ms): Measured jitter (difference between maximum and minimum one-way delay).
  • Received packets (packets): Number of received frames.
  • Lost packets (packets): Number of lost frames.
  • MOS: Estimated MOS calculated from network metrics.
  • ES (%): Aggregated errored second (ES) percentage.
  • SLA: Service level agreement fulfillment for the test or monitoring: equal to (100 – ES) %.
Have more questions? Submit a request


Powered by Zendesk