TDS on Professional Services

Hi,

for a service firm, when the payment is paid (Professional Fee + Service Tax), can someone help if the TDS should be applicable on the entire invoice value or is it only on Professional fee excluding Service Tax?

Eg:

Prof Fee  : Rs 100,000

Serv.Tax : Rs 10,300

Total : Rs 110,300

Is the TDS applicable on Rs 100,000 or on Rs 110,300 ???

if there is any ITO circular to this effect, it will be of help.

thanks,