gtps2m0y | ACF/SNA Data Communications Reference |
The Fast Transaction Processing Interface (FTPI) facility of the X.25 NCP Packet Switching Interface (NPSI) enhances the GATE facility. (GATE is General Access to X.25 Transport Extension.) GATE allows communications between non-SNA devices and a Communication and Transmission Control Program (CTCP) running under TPF or VTAM. A CTCP assumes control of the X.25 DTE/DCE interface protocol. The communications between a CTCP and the NCP is established through SNA sessions. With FTPI, all virtual circuit traffic is multiplexed on a single SNA session between the CTCP and NPSI.
Without the FTPI option, NPSI requires the traffic for each virtual circuit to flow on its own unique SNA session. By reducing the multiple sessions required for each virtual circuit to a single session for each NCP, the time to activate the network is greatly reduced, and less main storage is required by NPSI. FTPI also improves NCP performance by blocking several packets into a single PIU for transfer to the host. TPF similarly blocks output to the NCP.
The essential parts of FTPI support include:
For more information regarding coding of a GATE/FTPI CTCP, as well as more detailed information regarding NPSI and its command flows, see the NPSI Host Programming and the NPSI Planning and Installation.
The format of the traffic sent between NCP and TPF is shown in Figure 10. The data transferred is always complete messages and is prefixed by a command header. The header provides the data length, X.25 link identifier (MCH_ID), the virtual circuit identifier (VC_ID), and the correlation number. The correlation number is assigned to the virtual circuit by NPSI at CALL REQUEST time and is used for all control and data exchanges for the life of the virtual circuit. Figure 11 shows the data content of each of the FTPI commands.
Figure 10. FTPI Message Blocking Format. For additional information on the Q and D bits, see the NPSI Planning and Installation.
Figure 11. FTPI Command Content. As represented in this figure, the X.25 link identifier is MCH, the virtual circuit identifier is VC, and the correlation number is CN. Additional information on the FTPI command content is found in the NPSI Host Programming.
The input logic is located in OPZERO and provides demultiplexing support for message traffic received over an FTPI session. The flow of input processing follows:
The logic in the SNA Output (SOUTC) routine accumulates output destined for an FTPI session. The general SOUTC processing recognizes traffic destined for an FTPI LU and:
FTPI message traffic is presented to the application using the standard TPF API:
Similarly, the application sends output messages by issuing a ROUTC macro with the data in a core block and a register pointing to the RCPL. On input to the application, the message text starts with an FTPI command header as shown in Figure 10. Output sent by the application must also prefix the message text with an FTPI command header. Optionally, the PSV routine that handles the call setup and takedown for the X.25 resources supported by the FTPI multiplexed session can insulate the application from processing FTPI headers by also performing the FTPI header management. The PSV routine defined for the FTPI LU can remove the FTPI header from input messages and store for recall and appending to the corresponding output message.
Define the following to NPSI:
Define the following to the TPF system:
For more information about defining SNA resources to the TPF system, see Defining SNA Resources to the TPF System.
CTCP is the host LU that handles X.25 traffic. In VTAM, the CTCP is viewed as an intermediate program that translates between X.25 and SNA message formats. In TPF, you have different implementation choices for a CTCP. A TPF LU that serves the role of a CTCP can be any of the following:
The use of a PSV routine to intercept message traffic and modify TPF output processing is supported for the following resource types:
Regardless of the method used to create a CTCP LU, your application or PSV routine is responsible for translating between the data formats used by NPSI and those required by the TPF application.
The CTCP pseudo LU is an LU that serves as a port between FTPI and the CTCP. There is a difference between operating with or without FTPI. Without FTPI, NPSI requires an LU and a session for each virtual circuit; with FTPI, there is a single LU and a single session for each CTCP or host. The format and parameters used to define a CPLU are shown in Figure 12.
Figure 12. RSC Definition Statement for an FTPI LU
lu_name RSC LUTYPE=FTPI [,PACING=0|n] [,AWARE=YES|NO] [,PSV=name] [,LEID=nnnnnn] |
The description of the FTPI values are:
An example of the coding of the RSC statement for a CPLU is shown in Figure 13.
Figure 13. RSC Coding Example Statement for an FTPI LU
CPLU1 RSC LUTYPE=FTPI, PACING=0, AWARE=NO, PSV=FTPI |
See TPF ACF/SNA Network Generation for more information about the OSTG RSC statement.
The only VTAM consideration for FTPI support is to provide a default VTAM log mode definition for the FTPI LU, as shown in Figure 14.
Figure 14. VTAM Log Mode Entry for FTPI
FTPI MODENT FMPROF=X'03', FM Profile 3 TSPROF=X'03', TS Profile 3 PRIPROT=X'90', Exception response SECPROT=X'90', Exception response COMPROT=X'0040', Half-duplex contention RUSIZES=X'8989' Max 3860 in, 3860 out SSNDPAC=X'00' No send pacing SRCVPAC=X'00' No receive pacing PSERVIC=X'010000000000000000000000 LU type 1 |
For more information about the VTAM log mode definition, see VTAM Resource Definition Reference.
NPSI stage 1 user macros describe the X.25 network. The overall structure of the macro is shown in Figure 15. For additional information on the NPSI macros, see NPSI Planning and Installation.
Figure 15. Organization of NPSI Macros
X25.CPL One for each CTCP X25.NET One for each network X25.VCCPT X25.OUFT X25.MCH One per multi-channel link X25.LCG One per logical channel group X25.LINE One per virtual circuit X25.PU One per virtual circuit X25.END |
There are two macro changes to NPSI definition for FTPI:
The X25.CPL macro creates the NCP system generation statements to define a virtual link, PU, and LU. The virtual LU provides a port between NPSI and the CTCP for exchanging message traffic. One X25.CPL macro is required for each CTCP or TPF host. The macro format is shown in Figure 16.
Figure 16. Organization of X25.CPL Macro
X25.CPL CTCPNO=n, LOGAPPL=ctcp_name, MINDATA=mm, MAXTIME=time, MAXDATA=size, DLOGMODE=mode_name, MODTAB=mode_table |
The description of the X25.CPL macro values are:
The coding of X25.CPL card is shown in Figure 17.
Figure 17. CTCP Pseudo LU Coding Example
X25.CPL CTCPNO=0,LOGAPPL=NEFA,MINDATA=120,MAXTIME=10, X MAXDATA=35665 * X25.CPL CTCPNO=1,LOGAPPL=NEFB,MINDATA=121,MAXTIME=20 |
The parameter to indicate that the Fast Transaction Processing Interface (FTPI) option of NPSI is to be used is on the X25.MCH macro. An MCH macro is required for every X.25 physical link. The macro, with the operands specific to FTPI support, is shown in Figure 18.
X25.MCH FTPI=YES|CUD0|SUBD [,CTCP=(m1,m2,...mn)] [,CUD0=(n1,n2,...nn)] [,SUBD=(p1,p2,...pn)] |
The description of the X25.MCH values are:
or:
An example of the coding of X25.MCH card is shown in Figure 19. For additional information on coding the X25.MCH card, see the NPSI Planning and Installation.
Figure 19. X.25 Link Definition
X25.MCH ADDRESS=1, X FTPI=CUD0, X CUD0=(00,09,01), X CTCP=(01,02,03), X LCGDEF=(1,10), X PKTMODL=8, X FRMLGTH=3500, X TDTIMER=3, X LCN0=NOTUSED, X LLCLIST=(LLC4), X GATE=GENERAL, X MWINDOW=2 |
To allow traffic to flow between TPF and the network requires activating:
With FTPI there are two additional steps to the activation procedure:
Figure 20 summarizes the line flows needed to establish a session between the TPF CTCP and the FTPI pseudo LU. NPSI FTPI support uses a pseudo link, PU, and LU to provide a port or connection to the CTCP. Typically, the session between the CTCP and the FTPI LU is automatically activated when the VTAM operator requests activation of the pseudo link, PU, and LU.
Figure 20. Pseudo Link Activation
Figure 21 shows the activation of an X.25 link. The description is for a single link; however, in practice, a single operator command activates both the CTCP session and the X.25 links.
Figure 21. Multi-Channel Link Activation
The 3 traces provided for FTPI are: