The protocol is actually called 'scheme'. And it's lower case.
http://www.ietf.org/rfc/rfc2396.txt3.1. Scheme Component
Just as there are many different methods of access to resources,
there are a variety of schemes for identifying such resources. The
URI syntax consists of a sequence of components separated by reserved
characters, with the first component defining the semantics for the
remainder of the URI string.
Scheme names consist of a sequence of characters beginning with a
lower case letter and followed by any combination of lower case
letters, digits, plus ("+"), period ("."), or hyphen ("-"). For
resiliency, programs interpreting URI should treat upper case letters
as equivalent to lower case in scheme names (e.g., allow "HTTP" as
well as "http").
scheme = alpha *( alpha | digit | "+" | "-" | "." )