San Antonio, TX
Looks like someone wants help with homework. =)
To answer your "question":
Ensure the IAS service is running on Radius server
However, i suggest that what you may want to do is research into WHY this is the answer rather than have us tell you. It will make you a better tech.
Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so. -Douglas Adams