SNA Terms and Concepts
Basic APPN Concepts
•If the session partner is not on an adjacent node, the network node server for the LU requesting the session uses the network topology database to identify network nodes and intermediate transmission groups in the route to the session partner.
•If the session partner is on an end node, the end node (or its network node server) provides information about the link between the network node server and that end node (or the link between the end node and a connection network).
3.Excludes all network nodes and transmission groups that do not meet the specified characteristics for the session route.
4.Computes the optimal route for the session.
Depending on the specified class of service, the route calculation algorithm computes a weight value for each node and logical link and then totals the weights for each route. To select the optimal path, the network node computes the current
Intermediate routing enables an APPN network node to receive and route data destined for another node. The origin and destination of the data can be an end node, another network node, or a LEN.
Intermediate routing supports sessions between LUs that are not on adjacent nodes. After a route has been selected for a session, APPN network nodes in the route use intermediate routing to forward session data to the next node in the route.
Resource characteristics maintained by the topology database can include congestion status. If a network node becomes heavily congested, the network node can relay this information to other network nodes in the network, making the congested network node less likely to be included in session routes calculated for new sessions.
APPN provides two types of intermediate routing:
•In intermediate session routing (ISR), available in all network nodes, the network node keeps track of each intermediate session. Each intermediate node adjusts the pacing of session data to control the rate at which data flows between adjacent nodes. Each intermediate node can also perform segmentation and reassembly of segmented
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