Certificate Exchange - Negative MDN

Comment on draft-ediint-certificate-exchange-00.txt.

Please clarify the behavior in the case of a negative MDN.

After this paragraph of section 2.3
   Upon receipt of the CEM Request, the recipient trading partner 
   processes the transport message as normal and returns the MDN. The 
   recipient MUST return the MDN before parsing and interpreting the CEM 
   XML data. The returned MDN only provides information on the veracity 
   of the transport message and not the acceptance of the certificate 
   being exchanged. 
    
add this
	If the recipient rejects the Request message at the transport level, the recipient MUST return a negative MDN if an MDN is requested, and the recipient MUST NOT return a CEM Response.  The recipient has rejected the Request at the transport level, and does not process the Request further.  The initiator's behavior when receiving a negative MDN is not defined.  The initiator MAY retransmit the Request, after taking some action to correct the transport problem, or it may take some other action.

At the end of section 2.3, add
	If the initiator rejects the Response message at the transport level, the initiator MUST return a negative MDN if an MDN is requested.  The initiator has rejected the Response at the transport level, and does not process the Response further.  The recipient's behavior when receiving a negative MDN is not defined.  The recipient MAY retransmit the Response, after taking some action to correct the transport problem.