This is an example of a normal HTTP response by a WebDAV server:
HTTP/1.1 200 OK
Server: Microsoft-IIS/5.0
Date: Wed, 11 Jul 2001 20:43:45 GMT
Allow-Extension: urn:schemas:httpmail, http://schemas.microsoft.com/repl/
MS-Author-Via: DAV
Public-Extension: urn:schemas:httpmail, http://schemas.microsoft.com/repl/
Content-Length: 0
Accept-Ranges: rows
DASL: <DAV:sql>
DAV: 1, 2
Allow: OPTIONS, TRACE, GET, HEAD, DELETE, COPY, MOVE, PROPFIND, PROPPATCH, SEARCH, SUBSCRIBE, UNSUBSCRIBE, POLL, BDELETE, BCOPY, BMOVE, BPROPPATCH, BPROPFIND, MKCOL, LOCK, UNLOCK
Public: OPTIONS, TRACE, GET, HEAD, DELETE, PUT, POST, COPY, MOVE, MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, SEARCH, SUBSCRIBE, UNSUBSCRIBE, POLL, BDELETE, BCOPY, BMOVE, BPROPPATCH, BPROPFIND
MS-WebStorage: 6.0.5686
Cache-Control: private
However, if you use Web publishing to make this site available, ISA Server filters the Options field and returns the following canned response to the requesting browser:
HTTP/1.1 200 OK
Content-Length: 0
Date: Wed, 11 Jul 2001 20:44:38 GMT
Public: GET, HEAD, POST, PUT, DELETE, TRACE, OPTIONS, CONNECT
Allow: GET, HEAD, POST, PUT, DELETE, TRACE, OPTIONS, CONNECT
Cache-Control: private
As you can see, not all of the Options fields are passed to the client. This causes the client to be unable to connect.