Table of Contents Point-to-Point Protocol (PPP)

5.10 TCP/IP and X.25

IP-X25 is a standard protocol. Its status is elective.

For detail on the Internet Protocol on X.25 networks, please refer to RFC 877 and RFC 1356.

5.10.1 Implementations

MVS, VM, OS/2, OS/400 and AIX/6000 all support TCP/IP over X.25 networks.

5.10.1.1 MVS

The TCPIPX25 address space runs a VTAM application program called XNX25IPI, which is the interface between the TCPIP address space's IUCV driver and your X.25 network. XNX25IPI communicates with the NPSI (X.25 NCP Packet Switching Interface) in a front-end IBM 37XX Communications Controller.

For more details, please refer to the IBM TCP/IP Version 3 Release 1 for MVS: Customization and Administration Guide and X.25 Network Control Program Packet Switching Interface Planning and Installation.

5.10.1.2 VM

The X25IPI virtual machine runs a GCS (Group Control System) application program called X25IPI, which is the interface between the TCPIP virtual machine's IUCV driver and your X.25 network. X25IPI communicates with the NPSI (X.25 NCP Packet Switching Interface) in a front-end IBM 37XX Communications Controller.

For more details, please refer to the IBM TCP/IP Version 2 Release 3 for VM: Planning and Customization and X.25 Network Control Program Packet Switching Interface Planning and Installation.

The provides support for non-SNA users. It is designed to support communications between hosts running TCP/IP over an X.25 network. For more details, please refer to IBM 9370 Information System X.25 Communications Subsystem Description.

5.10.1.3 X.25 Scenario using the IBM 9370

• From System A, a user can access System B using the supported by TCP/IP. This is transparent for the user doing a TELNET or FTP, which are standard functions of TCP/IP.
• From System A to System C, the user enters the SNA world by an access to NPSI. Then we are in the VTAM area. The link between VTAM and TCP/IP is realized by X25IPI, which is a virtual machine owned by TCP/IP.
• From System A to System D, the TCP/IP connection is an SNA link over an X.25 network. Viewed from TCP/IP, the physical network can be any one supported by SNA.
• System B and System E may be linked through XI capabilities.

Note: The integrated into the IBM 9370 is only supported by the Virtual Telecommunication Access Method (VTAM). It is designed as a part of . On the other hand, the is supported only by TCP/IP.

Table of Contents 3745 and Ethernet Adapter