gtps2m0iACF/SNA Data Communications Reference

Low-Entry Networking (PUT 2.1) Environment

See IBM Systems Network Architecture Advanced Peer-to-Peer Networking Architecture Reference for additional information about the PU 2.1 environment.

Control Points

With PU 2.1 support, the SSCP is replaced by a control point (CP). The control point serves as a means of identifying the node externally. The CP name is used in qualifying communications with other nodes in the network.

Control LUs

Control LUs (CLUs) are the mechanisms used to establish LU-LU sessions in the PU 2.1 LEN environment. A VTAM application program called the logon manager (LM) appears to the TPF system as a CLU and has a CLU-CLU session with a TPF CLU over which session initiation requests are passed. Any terminal that is not at the level where it can send a BIND, must request an LU-LU session from its control point. For TPF applications, the VTAM control point views all TPF applications as running under the control of the logon manager. Therefore, it forwards all requests (CINITs) to the logon manager to be serviced. The logon manager includes the CINIT in a request sent on the CLU-CLU session to the TPF CLU that contains the TPF application. TPF then generates and sends the BIND request to the originating LU to establish the session.

When the TPF system is operating in LEN mode, the TPF CP name is different for each link connected to the TPF system. This allows a unique CLU to be defined for each link that is part of the logon manager design.

3174 APPN Considerations

When TPF is connected to a 3174 Advanced Peer-to-Peer Networking (APPN) controller, there is no VTAM system involved. Without a CLU-CLU session to transport session initiation requests, TPF has no way of sending a BIND request through the 3174 to the PS/2 computer, PS/2 devices, PS/2 units on the token ring. The PS/2 computer, PS/2 devices, PS/2 units must be independent LUs, capable of sending a BIND request to TPF. Only sessions using the LU 6.2 protocol are supported for a 3174 APPN connection.