C-Cubed Protocol Definition

C-Cubed is a protocol which is used to transfer data between a Microsoft Windows-based workstation (client) and MVS-based mainframe (server) computers. C-Cubed is at the application layer in the OSI model, and utilizes either a TCP or APPC transport layer to transfer data between the client and the server. The protocol is proprietary, meaning only products developed and marketed by C-Cubed can utilize the C-Cubed protocol. There is no published RFC (or any other) standard on the internals of the protocol or how it works.

APPC vs TCP/IP Connectivity Notes

The C-Cubed APPC Transaction Program provides both TCP/IP (EZAxxx) and APPC (ATBxxx) protocol support. A C-Cubed client running on a PC workstation can connect to the C-Cubed MVS server via TCP/IP or APPC.

When connecting via TCP/IP, the C-Cubed TCP Listener started task must be running in order to accept TCP/IP connections from remote C-Cubed client workstations. The C-Cubed TCP Listener started task simply starts an APPC Transaction Program session for the requesting TCP/IP client, and transfers socket control to it. This ensures that the connected user is running in the security context of their supplied MVS credentials, and not the started task security context.

When connecting via APPC, the C-Cubed APPC Transaction Program is started as part of the session request. This ensures that the connected user is running in the security context of their supplied MVS credentials, and not the APPC started task security context. The C-Cubed TCP Listener started task is not required if C-Cubed clients are connecting via APPC only.