clarification on MTA AE-title

[Kevin Jordan <[e-mail]>]

Section 20 of the Routing document says that X.400/88 MTA's will identify
themselves via the AE-title element of the A-Associate request/response
(AARQ and AARE APDU's).  However these APDU's don't really contain an
AE-title element.  They contain separate AP-title and AE-qualifier elements.
These combine to form an AE-title.

In the case where an MTA supports one application context, MHS-DS allows
the MTA to be defined using a single directory entry.  This entry combines
the attributes of applicationProcess and applicationEntity entries.  So,
what AP-title and AE-qualifier values should be sent/expected by such an
MTA?  The APDU definitions in X.227 indicate that AP-title and AE-qualifier
are both OPTIONAL.  One requirement explicitly stated in X.227 is that if
both are present, they must have the same form.  There appears to be no 
requirement that if one is present, the other must also be present.

Therefore, I suggest that we add some clarification to section 20.1 of the
Routing document.  It should say the following:

   The A-Associate request and response (AARQ and AARE APDU's) of X.227
   include separate AP-title and AE-qualifier elements.  These combine to form
   AE-title elements.

   In the case where an MTA supports one application context and is
   defined by a single directory entry, having no subordinate applicationEntity
   entries, the AP-title element shall be specified as the full distinguished
   name of the MTA, and the AE-qualifier element shall be omitted. In the
   case where an MTA supports more than one application context, so it is
   defined as an applicationProcess entry with one or more subordinate
   applicationEntity entries, the AP-title element shall be specified as the
   full distinguished name of the applicationProcess entry, and the
   AE-qualifier element shall be specified as the relative distinguished name
   of the subordinate applicationEntity entry representing the selected
   application context.