How ES/MSS Understands the Connection

The communication between ES/MSS and MFA Server uses a proprietary TCP/IP protocol that conveys the necessary LU6.2 protocol information in TCP/IP packets. The SYSIDs used in the MFA Server configuration are the key to this communication. In the example definitions, the target z/OS CICS system is identified as CICA and the target ES/MSS server is identified as MTO1. The initial connection messages between ES/MSS and MFA Server use these SYSID values to exactly identify the two target systems.

If ES/MSS initiates the socket connection to MFA Server, ES/MSS will send a "bind" packet for SYSID CICA. The bind packet also contains the SYSID of the originating MSS, MTO1. The initial packet from ES/MSS is identical to the initial packet from a CICS support client, so MFA Server needs to identify the type of requester. If MFA Server finds a definition for an ES/MSS server with a SYSID of MTO1 (the ID parameter in the MCO definition) and the request originated from the IP address specified in that definition, then MFA Server recognizes this as a request from an ES/MSS server. Otherwise, the connection is recognized as a request from a CICS support client.

At this point, it is important to note that support for CICS has been available in earlier versions of MFA Server and this support allows MFA Server clients to originate requests INTO a z/OS CICS system. This same level of support has also been used by ES/MSS systems, before the availability of the ES/MSS outbound feature. This level of support does not require a definition for the ES/MSS server and it does not require the ES/MSS outbound feature support. In this case, the only definition required is the definition of the target z/OS CICS system (number 2 in the diagram). If your only need is for ES/MSS requests into CICS, you may continue to configure your MFA Server in this way. However, our recommendation is that you follow the configuration requirements as outlined in this appendix and define a complete bi-directional connection for the systems that uses MFA Server's ES/MSS outbound feature. The extra effort is minimal and your systems will be ready to support CICS requests into ES/MSS, when they are needed. The complete configuration also results in each ES/MSS having a unique identity from the perspective of the z/OS CICS systems.

Once the initial connection is established, the ES/MSS and CICS definitions have been selected and MFA Server has all of the information it needs to accept a request from ES/MSS and send it into z/OS CICS over an LU6.2 ISC connection. MFA Server will allocate LU6.2 conversations using the MFAMTO1 ACB that has been defined for this ES/MSS. The conversation partner will be the z/OS CICS system that is using the ACB named CICSSYSA and the SNA session for the conversation will use the #INTER SNA logmode. The VTAM SNA logmodes are part of your VTAM SNA configuration and the suggested name can be changed to any other logmode name used for LU6.2 ISC connections in your system. Just be sure that the specified logmode definition is available to both MFA Server and CICS. The MFAMTO1 ACB name used in this sample definition is defined to the VTAM SNA network using a VTAM APPL definition. The APPL definition for MFAMTO1 is provided in another MFA Server sample, the MFAVTAM member in your <hlq>.CNTL data set. This member is installed in your VTAMLST definitions and activated during MFA Server installation.

Each ES/MSS server that you define must have its own ACBNAME and it is this ACBNAME that gives each server a unique identity in the z/OS CICS system(s).