These scenarios explain how system request processing works with multiple types of systems.
Scenario 1
All servers are iSeries™ servers. System request processing works normally.
The image depicts the following setup: Home system A in New York connects to intermediate system B in Chicago, which connects to intermediate system C in Los Angeles, which connects to end system D in Houston.
Scenario 2
The New York system is a non-iSeries server using 3270 or VTxxx Telnet.
The image depicts the following
setup: System A in New York, a non-iSeries server, connects to home system
B in Chicago, which connects to intermediate system C in Los Angeles, which
connects to end system D in Houston. 
The system request processing works like the first scenario except that Chicago is considered as the home system. All system requests sent to the home system process on the Chicago system.
Scenario 3
The Houston system is a non-iSeries servers using 3270 or VTxxx Telnet.
The image depicts the following setup:
Home system A in New York connects to intermediate system B in Chicago, which
connects to intermediate system C in Los Angeles, which connects to end system
D, a non-iSeries server in Houston. 
The system request processing works like the first scenario except that Los Angeles is considered as the end system for all system request processing. If you press the System Request key and then press the Enter key, the System Request menu for Los Angeles displays.
Scenario 4
The Los Angeles system is a non-iSeries server using 3270 or VTxxx Telnet.
Home system A in New York connects
to end system B in Chicago, which connects to non-iSeries server system C
in Los Angeles, which connects to home system D in Houston, which connects
to end system E in Tokyo. 
The system request processing works like the first scenario except that the Chicago system is considered as the end system for system request processing. If you press the System Request key and then press the Enter key, the System Request menu for Chicago displays.
If you want to send a system request to the Tokyo system, you can map a function key on the Houston system to the System Request key. If you map this function, then the Tokyo system is the end system, and Houston is the home system.
The image depicts the following setup: System A in New York connects to system B in Chicago, which connects to non-iSeries server C in Los Angeles, which connects to home system D in Houston, which connects to end system E in Tokyo.
As an example of this mapping function for an iSeries 3270 Telnet server, the default keyboard mapping identifies the System Request key as a 3270 PF11 key. For an iSeries 3270 Telnet client, the F11 key is mapped to the 3270 PF11 key. If the Los Angeles system is a system that uses the 3270 data stream, then pressing F11 maps the Los Angeles system to the System Request key on the Houston system. The system request transmits to the Tokyo system, and the System Request menu for Tokyo displays.