Session Routing - HP -UX SNAplus2 Administration Manual

An APPN end node can also receive (and respond to) LOCATE search
requests from its network node server to search for, or confirm the
continued presence of, specific LUs in the end node.
Each APPN end node registers its LUs with its network node server by
sending the network node a registration message. In this way, the
network node maintains current directory information for the end nodes
in its domain. A LEN node cannot register LUs with its network node
server. Therefore, all LUs on the LEN node must be predefined, through
configuration, to the network node server.

Session Routing

APPN supports the following dynamic route selection procedures:
• For sessions with adjacent nodes, direct session routing.
• For sessions that traverse one or more intermediate nodes, one of the
following:
• Intermediate session routing (ISR), which provides a route that
does not change during the course of the session.
• High-Performance Routing (HPR), which includes the Rapid
Transport Protocol (RTP) and automatic network routing (ANR)
facilities. RTP enables you to reroute session traffic around route
failures or congestion, and ANR minimizes cycles and storage
requirements for routing network layer packets through
intermediate nodes on a session route.
The APPN functions that provide dynamic route selection are known as
topology and routing services (TRS).
Topology and Routing Services
Each APPN node includes a topology database that stores information
about other APPN nodes and about transmission groups, which are sets
of links between a specific pair of nodes. The contents of the database for
a specific node depend on the node type:
• All network nodes share a copy of the network topology database.
This shared database includes information about all other network
nodes—including network IDs, CP names, and other node
characteristics—and about the transmission groups between each
pair of network nodes. This database provides a complete view of the
Chapter 1
SNA Terms and Concepts
Basic APPN Concepts
53