kit@gateway.mitre.ORG (03/18/91)
Regarding the AU delaying DN/NDN until Fax or Tlx message is sent successfully:
Presumably if the UA or AU is controlling whether the MTA generates
a DN or NDN, it would be done via the RESULT SET and ERRORS in the
response to the MessageDelivery Abstract Operation. The problem is
that the errors that can be indicated are not relevant to this case
of delivery error to the actual end recipient.
The errors listed in 1988 X.411 are
DeliveryControlViolated
SecurityError
UnsupportedCriticalFunction
You would also want errors such as
DecodeErrorOfMessageContents (if ASN.1 decode error)
TranslationFailureOfMessageContents (e.g., failure when translate TTX to FAX,
such as due to that translation not
having been implemented by that AU.)
TransmissionFailureToRecipient (e.g., due to network errors)
DeliveryFailureToRecipient (e.g., due to problems with recipient h/w,
or TLX answerback that didn't match)
UnrecognizedRecipient (e.g., error in recipient name that is not
detected by MTA)
IncompatibleMediaForRecipient (e.g., sending voice msg to telex recip)
ServiceSuspended (or -Terminated) (e.g., of either the AU service or the
service for a particular recipient)
TimeoutOnDelivery (or -Transmission) (if no ack received from tlx network)
UnsupportedServiceRequest (e.g., if postal service not supported)
RecipientDeviceBusy (or -NoAnswer) (e.g., for Fax phone number busy or NA)
ContentsTooLarge (e.g., a megabyte sent to tlx recip)
You could also have errors for preventing international telex or fax,
detecting routing loops between tlx network and X.400 network, etc.
I could go on forever with this...I will stop here.
Kit Lueder,
MITRE Corporation
(The statements here are my own opinions, not those of my employer.)