how to test QOS?

Hi,

How I can test my internet accesses to verify if the QOS is supported and
correctly used?

I have a VOIP server and an ISA Server, my VOIP server is setup to priorize
the delay.
So I want to verify that the packets are correctly scheduled and the
priority is correctly used.

which tool can I use to do this?

I don't have access to my internet router, I just have access to my servers.

Thanks for your guides and links.

Jerome.