X400: Transports Supported by the X.400 Gateway

MORE INFORMATION

The X.400 gateway supports multiple connections (two incoming and one outgoing) on either of these transports. These transport stacks are implemented according to International Standards Organization (ISO) Open Systems Interconnection (OSI) specifications:

                TP0
        |--------------------|
        |     Application    |\ 
        |--------------------|  \ 
        |     Presentation   |- \ \ 
        |--------------------|      > X.400 Gateway Layers
        |     Session        |- / / 
        |--------------------|  / 
        |     Transport      |/ 
        |--------------------|
        |     Network        |\ 
        |--------------------|  \ 
        |     Data Link      |---->   TP0/X.25 Layers
        |--------------------|  / 
        |     Physical       |/ 
        |--------------------|


                TP4
        |--------------------|
        |     Application    |\ 
        |--------------------|  \ 
        |     Presentation   |---->   X.400 Gateway Layers
        |--------------------|  / 
        |     Session        |/ 
        |--------------------|
        |     Transport      |\ 
        |--------------------|  \ 
        |     Network        |- \ \ 
        |--------------------|      > TP4/CLNP Layers
        |     Data Link      |- / / 
        |--------------------|  / 
        |     Physical       |/ 
        |--------------------|
				

NOTE: The TPO/X.25 works with the bottom three layers of the OSI stack, whereas TP4/CLNP works with the bottom four.