protocol: unrecognized protocolOp tag

[Hallvard B Furuseth <h.b.furuseth@usit.uio.no>]

[Protocol] 4.1.1 (Message Envelope) says:

   If (...) tag of the protocolOp is not recognized as a request, (...)
   then the server SHOULD return the Notice of Disconnection
   described in Section 4.4.1, with the resultCode set to protocolError,
   and MUST immediately close the connection.

In this case, I think it would be more useful if the server gave a
normal protocolError response and kept the connection open.  That
way, a client could test for the existence of a message type
extension simply by trying to use it.

-- 
Hallvard