When there is a single transport provider, and the relationship
of server to transport provider is 1:1, port management is relatively
simple. Using the PORT statement, the port number can be reserved
for the server in the PROFILE.TCPIP for that single transport provider.
Port management becomes more complex in a CINET environment where
there are multiple transport providers (multiple instances of TCP/IP)
and a potential for multiple combinations of the same server (for
example, z/OS® UNIX and TN3270E Telnet servers).
In a multiple transport provider environment, the following questions
need to be answered for each server in an installation:
- Is the server generic so that it can communicate with multiple
TCP/IPs or does the server have an affinity for one instance of the
transport providers and can communicate with only one TCP/IP?
- How can ports be reserved across multiple transport providers?
When is the port reservation determined by MVS™ rather than by the job name, procedure name,
or user ID?
- How can you synchronize between BPXPARMS and PORTRANGE for ephemeral
port reservation?
- How can TCP/IP distinguish between two different instances of
Telnet (z/OS UNIX Telnet and TN3270E Telnet servers)?