Specifications

110 IBM System z Personal Development Tool: Volume 3 Additional Topics
Figure 10-2 Shared Ethernet adapter
The awsosa device manager is independent from Linux TCP/IP, although it can use the same
Ethernet adapter. Up to 16 TCP/IP stacks (in z/OS or z/VM) can connect to the awsosa
device manager. Each of these TCP/IP stacks defines its own IP address. The configuration
shown in Figure 10-2 would have two IP addresses, one for Linux TCP/IP and one for z/OS
TCP/IP. These IP addresses are unrelated. External routing rules typically require that both IP
addresses be on the same subnet, but this rule is external to the 1090. (Many examples in
this documentation series use 192.168.0.60 for the Linux IP address and 192.168.0.61 for the
z/OS IP address.)
The system in this illustration provides two paths for a user to connect to z/OS TSO. One path
is through Linux TCP/IP and the aws3274 device manager. The other path is through the
awsosa device manager and z/OS TCP/IP. (In this illustration, the awsosa port could be
operating in either QDIO or non-QDIO mode.)
Note that there is no connection between OSA and the base Linux in this situation. It is a
Linux design oddity that the two users of the physical Ethernet interface cannot communicate
with each other.
Note these differences:
򐂰 The first path mentioned does not involve z/OS TCP/IP. The TN3270e client connects to
the IP address used by the base Linux system. The client also specifies the port number
assigned to the aws3274 device manager; this is port 3270 in our examples. z/OS accepts
the connection as a coax-attached local 3270 terminal and is unaware that the client is
actually connected via Linux TCP/IP. For this operation the z/OS OSA and TCP/IP
functions need not be implemented. The MVS console must use this path.
򐂰 The second path uses a different IP address for OSA connections (assigned by z/OS
PROFILE statements, or equivalent). z/OS TCP/IP internally passes TN3270e client
connections to VTAM and thence to TSO. z/OS TCP/IP can also manage ftp sessions,
telnet sessions, and so forth. The MVS console cannot use this path.
Linux
Linux TCP/IP
System z
Device managers
ftp user Telnet TN3270e Browser Telnet
PC system
TN3270e ftp
Different IP
addresses
One Ethernet port
for everything
awsosa
TSO
ftp Telnet server
ftp
TCP/IP
IOS
aws3274
x3270
VTAM