1 Scope
The procedures specified in this International Standard do not prevent communication between transport entities conforming to ISO/IEC 8073 only and those conforming to ISO/IEC 8073 as well as to this International Standard.
The use of a protocol identification procedure allows transport entities to be implemented which can support both the OSI transport protocols and non-OSI protocols above the OSI network layer.
NOTE - The use of NSAP addresses as it is defined in ISO/IEC 7498-3 provides another possibility in distinguishing between OSI and non-OSI users of the network service. If however the use of NSAPs incurs unacceptable penalties, for example where each NSAP is charged for by the network provider, then the transport protocol identification mechanism is available.