The present document describes the additions to the ISDN User Part (ISUP) for providing a transport mechanism used
by applications requiring a bearer in conjunction with the support of the applications signalling information flow. It
specifies the Application Transport Mechanism (APM) for the pan-European Integrated Services Digital Network
(ISDN) as provided by the European public telecommunications operators. This transport mechanism shall provide the
same capabilities as the Transaction Capabilities Application Part (TCAP) provides to its users. The definition of the
applications that use this mechanism are documented in their own specification and are therefore outside the scope of
the present document.
The Application Transport Mechanism (APM) is capable of creating signalling associations between APM-user
application logic located at a Public Initiating Node (PIN) and its peer APM-user application logic located at the Public
Addressed Node (PAN).
This transport mechanism provides the APM-user applications (APM2000-user applications) with both an implicit and
an explicit APM addressing capability. The applications originally designed to use the APM 98 [3] (APM98-user
applications) can be supported without alterations by the mechanism described in the present document. APM98-user
and APM2000-user applications are differentiated by their application context identifiers.
The coexistence along a call path of nodes with the APM 98 capability and nodes supporting the APM 2 000
functionality may cause in two very specific configurations an inappropriate handling of application transport
parameters sent by an APM 2000-user application.
1) The first scenario is the following:
- an APM 2 000-user application sends information at call set-up towards a remote application,
- an intermediate node supporting the previous APM version [3] is encountered in the call path before the node
where the application i (...abbreviated)