gtpc1m0hTransmission Control Protocol/Internet Protocol

Data Flow between the Offload Device and the TPF System

The TPF system implementation of TCP/IP support is based on the IBM 3172 Model 3 Interconnect Controller with the TCP/IP Offload program and supports applications using the Berkeley Software Distribution (BSD) standard socket API functions to communicate with the Internet.

See Socket Overview for a discussion of socket programming concepts used by TCP/IP support. Figure 6 shows the data flow between the TPF system and the IBM 3172 Model 3 Interconnect Controller. The following steps correspond to numbers in Figure 6:

  1. An application in the TPF system issues a socket API function and the socket API is forwarded to the TPF socket API support component.
  2. The TPF socket API support component builds an inter-user communication vehicle (IUCV) message that contains the socket API function call, parameters, and user data. This message is transmitted through the TPF CLAW device interface to the IBM 3172 Model 3 Interconnect Controller.
  3. The return code from the IBM 3172 Model 3 Interconnect Controller is returned to the application.

Figure 6. TPF Implementation of the IBM 3172 Model 3 Interconnect Controller with the Offload Program