During route computation, APPN determines the optimum route
through a network in the following steps:
- obtains the required route characteristics from the COS database
using the mode name specified in the session request
- determines all possible combinations of transmission groups and
nodes that form a route to the destination database
- the actual characteristics of the Nodes and TGs in these routes are
compared against the COS tables that contain the required
characteristics of the session. A weight is assigned based on how
well the actual characteristics meet the required characteristics.
Where there is no match between actual and required
characteristics, the route containing the node or TG is excluded
from further computation.
- Each possible route is quantified by adding the weights assigned
to the node and TGs in the route. The route with the lowest weight
is the one used for the session.
This attribute is part of the COS tables and specifies the minimum
cost per byte allowed for a TG to be used for a session. It is a single
byte value in the range 0 to 255 that expresses a relative cost of
transmitting a byte over the associated TG. The units for cost per
byte are user defined. Like cost per connect time, cost per byte is
network specific and will not be uniform across networks unless
assignments are coordinated.