HP-UX SNAplus2 General Information (October 1998)

18 Chapter 1
SNA Networking
Components of a Subarea Network
Additionally, the SSCP establishes a session to the remote LU (the
SSCP-LU session). The SSCP-LU session is used to control and manage
both the LU itself and the session between the host and remote LUs. The
remote LU uses the SSCP-LU session to request the SSCP to establish a
session between the host and remote LUs (the LU-LU session).
When a session is requested, the SSCP manages the host LU to establish
the LU-LU session with the remote LU. The LU on the host is called the
“primary LU”; it initiates the LU-LU session and is also able to
terminate the session. The LU on the remote node is called the
“secondary LU”; it responds to the session initiation but is unable to
initiate or terminate sessions in its own right.
Peer-to-Peer Connections
The description of the remote node in a subarea network assumes that
the remote node is a type 2 node, which can communicate only with a
host system. In more modern subarea networks, however, pairs of type
2.1 nodes (such as SNAplus2) can communicate without needing to send
information through the host. Each node is configured with information
about the other node's LUs; the nodes can then use a direct
communications link to establish LU-LU sessions.