Hi Greg,
I am not sure i get the question properly. But client authentication is part of SSL handshake process where client is also challenged for its certificate which is verified by server/ACE and the process proceeds further. This is more secure since client identity is also being verified. For HTTP sites, there is no ssl and hence this step is irrelevant.
If this is not what are you asking, please elaborate a bit and i will answer.
Regards,
Kanwal
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