Connections through boundary function-based transmission groups

Nodes are connected by transmission groups (TGs). A TG connects a pair of adjacent link stations across the transmission medium. A boundary function (BF)-based APPN TG is used to connect two APPN nodes that use the NCP or VTAM® boundary function.

Transmission groups are described with the following standard APPN characteristics:

Cost per connect time
Cost per byte
Security
Propagation delay
Effective capacity
User-defined values

The values specified for these characteristics are saved in the topology database and are used to determine the weight of the TG for route calculation. The values you specify represent the characteristics of the link; the values do not affect the actual physical characteristics of the link. If the physical characteristics of the link change, the values specified for the TG characteristics should probably be changed to reflect the new physical characteristics. For more information about the topology database, see Topology database.

By default, all TGs assume the same characteristics. To distinguish one TG from another, TG characteristics can be specified in the following ways:

As TG profiles, which are groups of TG characteristics that can be applied to several PUs
On definition statements

The characteristics of TGs owned by other nodes are learned through topology database updates (TDUs).