compatibility
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qop-options
This directive is optional, but is made so only for backward
compatibility with RFC 2069(-> 2617draft) [6]; it SHOULD be used by all
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... in WWW- Authenticate. This directive is optional in order to
preserve backward compatibility with a minimal implementation of
RFC 2069(-> 2617draft) [6 ...
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If the "qop" directive is not present (this construction is for
compatibility with RFC 2069(-> 2617draft)):
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