When making a twping RPC call, you can specify the number of test sessions to create. However, because each session requires a port, if you specify a port range such that the number of ports is fewer than the number of test sessions, the following error message is returned.

[port-range] Size of the port-range must be at least as large as session-count

To prevent this error from occurring, make sure that you specify a wide port range in the RPC call. If you do not specify a port range, make sure that you do not specify more than 201 test sessions in the call because the default range (8760 through 8960) accommodates as many as 201 ports.

The following example shows the XML structure of a twping RPC call in which the number of test sessions is greater than the number of ports in the port range.

<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="3">
  <twping xmlns="urn:vyatta.com:mgmt:vyatta-service-twamp:1">
    <host>localhost</host>
    <session-count>100</session-count>
    <port-range>
      <start>8000</start>
      <end>8005</end>
    </port-range>
  </twping>
</rpc>]]>]]>