The implementation of EE in z/OS involves data transfer between the VTAM and the TCP/IP address spaces. A special connection type called IUTSAMEH is used to move data from VTAM to TCP/IP and vice versa.

This connection type is used to connect two or more Communications Server for z/OS IP stacks running on the same MVS image. In addition, it is used to connect Communications Server for z/OS IP stacks to z/OS VTAM for use by Enterprise Extender.

For Enterprise Extender, z/OS Communications Server implements a separate UDP layer called "Fast UDP" that is optimized for Enterprise Extender communication. Fast UDP, communicates with Enterprise Extender (the APPN over UDP component in VTAM through the IUTSAMEH device.

Figure 1 illustrates the Enterprise Extender components in z/OS and the data flow among these components.

Figure 1. Internal Enterprise Extender data flow on z/OS