White Paper
SNI Replacement
The IBM Communications Controller, commonly known as the front-end processor (FEP), has been used for many specific functions during the several decades that it served as a network attachment point for IBM mainframes. Of these, almost all either have been rendered obsolete or are now being done by more modern equipment. The only significant exception to this change is a function known as SNA Network Interconnection (SNI). SNI is the connection, by gateways, of two or more independent SNA networks to allow communication between logical units (LUs) in those networks. In many cases FEPs that were purchased to support hundreds or thousands of networks devices are now being used to support a very small number of attachments to other SNA networks. This may create an extremely inefficient use of resources and a disproportionate cost to benefit. The largest impediment to replacing this technology is usually a result of it being embedded in at least two separate organizations, meaning that both must simultaneously agree to change.
The general advice from Cisco is to replace SNI at the application level. For each business function that is being performed through an SNI connection, there is almost certainly a readily available equivalent solution that uses the open IP protocol for connectivity.
Cisco acknowledges, however, that there are cases where an SNA-based alternative may be more expedient and, equally important, may require less inter-company agreement. This paper addresses these scenarios, first showing the parameters for the typical configuration that uses FEPs at both organizations, and then four alternatives that continue to use SNA but allow either one or both of the organizations to decommission their FEPs.
This paper details the following five SNI and SNI replacement configuration examples:
- Back-to-back configuration
- Extended Border Node (EBN) over Enterprise Extender (EE) connections
- Single-sided (adjacent) SNI configuration
- Advanced Peer-to-Peer Networking (APPN) EBN over a Layer 2 SNA link
- Casual Connection
Example 1: Back-to-Back Configuration
The back-to-back configuration is the current configuration in many cases. It is included here to show the "before" picture: two gateway Virtual Telecommunications Access Methods (VTAMs) and two gateway Network Control Programs (NCPs) that connect through a null network (see Figure 1). According to recent Cisco surveys, this is the most popular configuration used between client and partner networks.
Figure 1 Back-to-Back Configuration
Replacing a back-to-back SNI connection to a partner's network requires changes to VTAM and changes and additions to the partner's VTAMs, gateway NCP, and subarea path definitions. The source statements for the gateway NCP-NCP04 are as follows:
OPTIONS NEWDEFN=(YES,ECHO,SUPP,REUSE)
***********************************************************************
* CISCO - BACK-TO-BACK CONFIGURATION *
* NET01.MVS2----NCP03—---SA13----NETX—--SA14----NCP04-----NET05.MVS6 *
***********************************************************************
***************************** M * *
* ACF/NCP FOR PDVC 3745 * S * SUBAREA = 04 *
***********************************************************************
* PCCU SPECIFICATIONS - ACF/VTAM NCP04 (SUBAREA 04) *
***********************************************************************
AUTOIPL=YES, LOAD 37XX IF FOUND IN LOAD MODE *
AUTOSYN=YES, TELL VTAM NCP NAME *
BACKUP=YES, TELL VTAM NCP NAME *
VFYLM=YES ASK OPERATOR BEFORE LOADING
**********************************************************************
BUILD STATEMENT SPECIFICATIONS **
**********************************************************************
CPBUILD BUILD BFRS=(240), NCP BUFFER SIZE,EP FREE BUFFER *
NETID=NET05, NATIVE NETWORK NAME *
USGTIER=1, NCP USGAE TIER *
CSMHDR=27F5C711C3F0405C40C8C4D9405C, 3270 CRITSIT HDR *
CSMHDRC=40E3C5E7E3405C5C, 3270 CRITST HEADER XTRA TXT *
CSMSG=C3D9C9E3E2C9E35A40E385819440F040, CRITSIT MESG *
CSMSGC=6040C1D5E240828587A4954B, CRITST MESG XTRA TXT *
CWALL=50, MIN. BUFFERS BEFORE SLOWDOWN *
DSABLTO=11.5, DATA SET READY TIME OUT=11.5 SEC *
ENABLTO=11.5, IBM 386X REQUIRE 6.5 AS MINIMUM *
HPR=YES, IBM 386X REQUIRE 6.5 AS MINIMUM *
NUMHSAS=6, UP TO 6 CONCURRENT HOSTS *
LOADLIB=LOADLIB, DDNAME FOR VTAM TO FIND NCP LOADLIB *
MAXSSCP=8, 8 SSCP'S CAN ACTIVATE THIS NCP *
MAXSUBA=63, ALLOW FOR UP TO 63 SUBAREAS *
NAMTAB=50, INDEPENDENT LU SUPPORT *
SUBAREA=04, SUBAREA ADDRESS = 04 *
MODEL=3745-170, LOAD MODULE FOR A 3745 CONTROLLER *
SLODOWN=12, % OF BUFFERS LEFT *
TYPSYS=OS, OS/MVS GENERATION *
VERSION=V7R7, NCP VERSION 6 RELEASE 2.0 *
NEWNAME=NCP04, MEMBERNAME IN LOADLIB AND VTAMLST *
TYPGEN=NCP, NCP ONLY, NO EP OR PEP *
VRPOOL=128, NUMBER OF VR POOL *
NETLIM=500, HSCBS ASSIGNED AT ONE TIME TO ALL ADDRS *
HSBPOOL=150 HALF-SESSION CBS FOR XNET SSCPS AND LUS
***********************************************************************
* SYSCNTRL STATEMENT SPECIFICATIONS *
***********************************************************************
**NOTE: IF THE NCP DOES NOT CONTAIN START/STOP OR BSC DEVICES, *
** SYSCNTRL OPTIONS WILL NOT BE INCLUDED IN THE ACF/NCP/VS *
** GENERATION EVEN IF INCLUDED IN THE SOURCE DECK *
SYSCNT03 SYSCNTRL OPTIONS=(BHSASSC,ENDCALL,MODE,RCNTRL,RCOND,RECMD,RIMM*
,NAKLIM,SESSION,SSPAUSE,XMTLMT,STORDSP,DLRID,RDEVQ)
***********************************************************************
***********************************************************************
PHOST05 HOST MAXBFRU=64, *
***********************************************************************
* PREDEFINED NON-NATIVE NAU'S FOR CROSS-NETWORK SESSIONS *
***********************************************************************
***********************************************************************
***********************************************************************
PPOOL09 PUDRPOOL NUMBER=500
LPOOL09 LUDRPOOL NUMILU=750,NUMTYP1=750,NUMTYP2=750
***********************************************************************
***********************************************************************
VR0=0,VR1=1,VR2=2,VR3=3,VR4=4 8 S
***********************************************************************
* GROUP SPECIFICATION FOR SDLC LINES *
***********************************************************************
G07STP SDLCST GROUP=G07NCPP, ASSOCIATED GROUP *
MAXOUT=7, FULL DUPLEX FACILITY *
MODE=PRIMARY, NON-RETURN-TO-ZERO-INVERTED *
PASSLIM=254, REPLY TIME-OUT= 1 SECOND *
RETRIES=(7,7,15) 7 RETRIES PAUSE 4 SECONDS 5 TIMES
G07STS SDLCST GROUP=G07NCPS, ASSOCIATED GROUP *
MAXOUT=7, FULL DUPLEX FACILITY *
MODE=SECONDARY, NON-RETURN-TO-ZERO-INVERTED *
PASSLIM=254, REPLY TIME-OUT= 1 SECOND *
RETRIES=(7,7,15) 7 RETRIES PAUSE 4 SECONDS 5 TIMES
***********************************************************************
* GROUP SPECIFICATION FOR NCP-NCP LINKS *
***********************************************************************
G07NCPS GROUP LNCTL=SDLC, *
G07NCPP GROUP LNCTL=SDLC, *
G80NCPP GROUP LNCTL=SDLC, *
***********************************************************************
* PU4 TO PU4 NCP04---NCP03 *
***********************************************************************
L0916 LINE ADDRESS=(16,FULL), USE ONE ADDRESS *
DUPLEX=(FULL), REQUEST TO SEND ALWAYS UP *
CLOCKNG=DIRECT, CLOCKING BY 3745 *
P0916A PU PUTYPE=4,NETID=NETX, *
CAN09 GROUP LNCTL=CA CHANNEL ADAPTER GROUP
CA1N09LN LINE CA=TYPE6,ADDRESS=00 FIRST CHANNEL ADAPTER
CA1N09PU PU PUTYPE=5,TGN=1,NETID=NET05
***********************************************************************
***********************************************************************
NET01 NETWORK SUBAREA=13, *
GWNAU NETID=NET05,NAME=MVS6,ELEMENT=1,NUMSESS=5
PATH DESTSA=04,ER0=(04,1),VR0=0,ER1=(04,1),VR1=1, *
VRPWS00=(2,6),VRPWS01=(2,6),VRPWS02=(3,9), *
VRPWS10=(2,6),VRPWS11=(2,6),VRPWS12=(3,9)
************************************************************************
* E N D E N D E N D E N D E N D E N D E N D E N D *
***********************************************************************
The source statements for the Cross Domain Resource Manager (CDRM) in NET05 VTAM are as follows:
***********************************************************************
* NET05 VTAM LIST FOR SNI BACK-TO-BACK CONNECTIONS *
***********************************************************************
* CDRM FOR BACK-TO-BACK SNI CONNECTION *
***********************************************************************
NET5M6M2 NETWORK NETID=NET01
MVS2MVS6 CDRM CDRDYN=YES,CDRSC=OPT,ISTATUS=ACTIVE
The NET05 VTAM PATH definition statement for NCP04 is as follows:
***********************************************************************
***********************************************************************
NCPSA04 PATH DESTSA=04, X
The source statements for the gateway NCP NCP03 are as follows:
OPTIONS NEWDEFN=(YES,ECHO,SUPP,REUSE)
***********************************************************************
* NCP03 - BACK TO BACK SNI DEFINITIONS *
* NET01.MVS2--NCP03<--SA13------NETX----SA14----->NET04----NET05.MVS6 *
***********************************************************************
***********************************************************************
***************************** M * *
* ACF/NCP FOR SNI 3745 * S * SUBAREA = 03 *
***********************************************************************
* PCCU SPECIFICATIONS - ACF/VTAM N06 (SUBAREA 11) *
***********************************************************************
AUTOIPL=YES, LOAD 37XX IF FOUND IN LOAD MODE
AUTOSYN=YES, TELL VTAM NCP NAME
BACKUP=YES, TELL VTAM NCP NAME
VFYLM=YES ASK OPERATOR BEFORE LOADING
***********************************************************************
* BUILD STATEMENT SPECIFICATIONS **
***********************************************************************
NCPBUILD BUILD BFRS=(240), NCP BUFFER SIZE,EP FREE BUFFER
NETID=NET01, NATIVE NETWORK NAME
USGTIER=1, NCP USGAE TIER
CSMHDR=27F5C711C3F0405C40C8C4D9405C, 3270 CRITSIT HDR
CSMHDRC=40E3C5E7E3405C5C, 3270 CRITST HEADER XTRA TXT
CSMSG=C3D9C9E3E2C9E35A40E385819440F040, CRITSIT MESG
CSMSGC=6040C1D5E240828587A4954B, CRITST MESG XTRA TXT
CWALL=50, MIN. BUFFERS BEFORE SLOWDOWN
DSABLTO=11.5, DATA SET READY TIME OUT=11.5 SEC
ENABLTO=11.5, IBM 386X REQUIRE 6.5 AS MINIMUM
HPR=YES, IBM 386X REQUIRE 6.5 AS MINIMUM
NUMHSAS=6, UP TO 6 CONCURRENT HOSTS
LOADLIB=LOADLIB, DDNAME FOR VTAM TO FIND NCP LOADLIB
MAXSSCP=8, 8 SSCP'S CAN ACTIVATE THIS NCP
MAXSUBA=63, ALLOW FOR UP TO 63 SUBAREAS
NAMTAB=50, INDEPENDENT LU SUPPORT
SUBAREA=03, SUBAREA ADDRESS = 11
MODEL=3745-170, LOAD MODULE FOR A 3745 CONTROLLER
SLODOWN=12, % OF BUFFERS LEFT
TYPSYS=OS, OS/MVS GENERATION
VERSION=V7R7, NCP VERSION 6 RELEASE 2.0
NEWNAME=NCP03, MEMBERNAME IN LOADLIB AND VTAMLST
TYPGEN=NCP, NCP ONLY, NO EP OR PEP
VRPOOL=128, NUMBER OF VR POOL
NETLIM=500, HSCBS ASSIGNED AT ONE TIME TO ALL ADDRS
HSBPOOL=150 HALF-SESSION CBS FOR XNET SSCPS AND LUS
***********************************************************************
* SYSCNTRL STATEMENT SPECIFICATIONS *
***********************************************************************
**NOTE: IF THE NCP DOES NOT CONTAIN START/STOP OR BSC DEVICES, *
** SYSCNTRL OPTIONS WILL NOT BE INCLUDED IN THE ACF/NCP/VS *
** GENERATION EVEN IF INCLUDED IN THE SOURCE DECK *
SYSCNT03 SYSCNTRL OPTIONS=(BHSASSC,ENDCALL,MODE,RCNTRL,RCOND,RECMD,RIMM
,NAKLIM,SESSION,SSPAUSE,XMTLMT,STORDSP,DLRID,RDEVQ)
***********************************************************************
***********************************************************************
***********************************************************************
* PREDEFINED NON-NATIVE NAU'S FOR CROSS-NETWORK SESSIONS *
***********************************************************************
***********************************************************************
***********************************************************************
PPOOL11 PUDRPOOL NUMBER=500
LPOOL11 LUDRPOOL NUMILU=750,NUMTYP1=750,NUMTYP2=750
***********************************************************************
***********************************************************************
VR0=0,VR1=1,VR2=2,VR3=3,VR4=4
***********************************************************************
