http

Dear Mr.

We have read the paper "Hypertext Transfer Protocol-- HTTP/1.1". It was
issued by your orgniazation. About proxy, we don't know how to send an
application to a proxy server through HTTP/1.1. We want to know the
structure of "challenge" and "credentials" used in Proxy-Authorization
and Proxy-Authentication also.

We are looking forward to hearing from you. 

Thanks a lot!