gtps2m4d | ACF/SNA Data Communications Reference |
A TPF Communications and Transmission Control Program (CTCP) is a user-written control program that manages the data flow between devices accessed through a Packet Switched Data Network (PSDN) and existing or new TPF applications. A TPF CTCP is a collection of one or more ECB-controlled programs implemented as a standard TPF application or as a Process Selection Vector (PSV). The main difference of implementing a CTCP as a TPF application, versus a TPF PSV, is related to which side of the TPF ROUTC Application Program Interface (API) the CTCP processing occurs.
A CTCP is required when either a Generalized Access to X.25 Transport Extension (GATE) or Dedicated Access to X.25 Transport Extension (DATE) is specified as an NCP Packet Switching Interface (NPSI) option for handling an X.25 link connected to a PSDN. The information presented in this appendix is based upon the requirements of an interface between a TPF/CTCP and the NPSI/GATE option.
The following sections cover a suggested X.25 Control Block structure to be defined by you for a GATE CTCP implementation using PSV routines to handle X.25 commands and X.25 data messages. These sections are based on the flows shown in Figure 102 and Figure 103.