OSI/AS Configuration and Management Manual

Installing and Configuring the Subsystem
OSI/AS Configuration and Management Manual—424119-001
4-25
Configuring Loopback Connections
Notice in Figure 4-2 that the called end (the end that issues an attach request) still
creates TAPS, TSP and NSP subdevices, but the calling end (the end that issues a
connect request) creates only a TAPS subdevice. This occurs because the called end is
waiting for a connection and has no prior knowledge of what kind of connection may be
requested; the calls may be external or internal—they are transparent to the called end.
Therefore, the called end must create the appropriate subdevices in each layer. The
calling end, however, determines that the called address is located in the same
subsystem, bypasses its own TAPS process (if the connection is configured for
loopback), locates the appropriate remote TAPS process, and adds a separate subdevice
to that process. The two loopback subdevices communicate with each other within the
same TAPS process.
Figure 4-2. Loopback Connection
042CDT .CDD
Application
TAPS
TSP
NSP
Connect Request
on System A
Application
TAPS
TSP
NSP
Attach Request
on System B
LAN or X.25
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