HP HP-UX SNAplus2, Administration Manual

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Chapter 1 37
SNA Terms and Concepts
Basic SNA Concepts
Before an SSCP-LU session can be established, the PU
controlling the LU must have an active SSCP-PU
session with an SSCP on a type 5 node. The SSCP-PU
session is used to pass control data and network
management data between the PU and SSCP.
CP-CP sessions
In an APPN network, adjacent nodes establish CP-CP
sessions. These sessions are used to search for a
resource in the APPN network and to maintain
topology information (see “APPN Control Point”).
Logical Unit Attributes for Sessions
Logical units have attributes that determine how they interact during
LU-LU sessions. These attributes are determined by the architecture of
SNA. LUs can be primary or secondary, and dependent or independent.
Primary and Secondary LUs.
To establish a session, one LU
requests session activation by sending a BIND request to another LU:
• A primary LU is the LU that sends the
BIND
request for a given
LU-LU session.
• A secondary LU is the LU that receives the
BIND
request.
Peer networks do not use a fixed hierarchy of nodes and do not have
predetermined primary or secondary LUs.
NOTE In a peer network, an independent LU that is participating in multiple
sessions (see “Multiple and Parallel Sessions”) can act as a primary LU
for one session and a secondary LU in another.
Dependent and Independent LUs.
All type 0, 1, 2, and 3 LUs are
dependent LUs. Type 6.2 LUs can be configured as either dependent or
independent LUs.
• A dependent LU (also known as an SSCP-dependent LU) requires the
services of an SSCP to establish a session with another LU. An
SSCP-LU session must be established before a dependent LU-LU
session can be established.
A dependent LU can be in session only with LUs on an SNA host.
Because of this restriction, dependent LUs usually use subarea
networks (also known as host-mediated networks). However, the