A useful tool to stresstest your VoIP server or PBX: 
<a href="http:&#x2F;&#x2F;www.mizu-voip.com&#x2F;Software&#x2F;VoIPTester.aspx" rel="nofollow">http:&#x2F;&#x2F;www.mizu-voip.com&#x2F;Software&#x2F;VoIPTester.aspx</a>