Class of service (CoS)

An APPN class of service (CoS) defines the required or requested characteristics of a route for a session. A class of service consists of a set of ranges of acceptable values for the characteristics of links and nodes to be used for a session specifying that particular class of service.

APPN classes of service are defined in a VTAMLST definition list. Unlike the class of service for the subarea network, where the class of service is actually a list of VRs that are acceptable for a particular class of service, APPN class of service specifies the types of routes that are acceptable for a class of service.

Each APPN class of service has a table of definitions.
Each column represents a transmission group or node characteristic.
Each row represents a "class" of transmission groups or nodes; see Table 1.

Table 1. #CONNECT class of service LINEROW values
LINE ROW	CAPACITY	COSTBYTE	COSTIME	PDELAY	SECURITY	Weight
1	4M MAXIMUM	0 0	0 0	MINIMUM NEGLIGIB	UNSECURE MAXIMUM	30
2	56000 MAXIMUM	0 0	0 0	MINIMUM TERRESTR	UNSECURE MAXIMUM	60
3	19200 MAXIMUM	0 0	0 0	MINIMUM TERRESTR	UNSECURE MAXIMUM	90
4	9600 MAXIMUM	0 0	0 0	MINIMUM TERRESTR	UNSECURE MAXIMUM	120
5	19200 MAXIMUM	0 0	0 0	MINIMUM PACKET	UNSECURE MAXIMUM	150
6	9600 MAXIMUM	0 128	0 128	MINIMUM PACKET	UNSECURE MAXIMUM	180
7	4800 MAXIMUM	0 196	0 196	MINIMUM MAXIMUM	UNSECURE MAXIMUM	210
8	MINIMUM MAXIMUM	0 255	0 255	MINIMUM MAXIMUM	UNSECURE MAXIMUM	240

Note the following:

Each row is defined by (min/max) range for each characteristic.
Each row defines a weight for transmission groups or nodes that fit the range.
Rows are typically defined from most to least restrictive (low weight to high weight).

Session paths in VTAM

VTAM chooses a route by comparing the actual characteristics of the available nodes and transmission groups to the allowed characteristic ranges specified in the requested class of service. For each APPN class of service entry, there are 1 to 8 LINEROW operands and 1 to 8 NODEROW operands. These operands give up to 8 acceptable sets of characteristics for the lines and up to 8 for the nodes in each class of service.

The WEIGHT parameter on the NODEROW and LINEROW operands is coded to indicate the desirability of that set of characteristics. The lower the value of the WEIGHT parameter, the higher the desirability of a node or transmission group that fits that set of characteristics.

The values shown in Table 1 for capacity, cost per byte, cost per unit of time, propagation delay, security level, and the user-defined characteristics (UPARM1, UPARM2, and UPARM3) represent ranges, with the top value in a LINEROW representing the minimum value and the bottom value in a LINEROW representing the maximum value. These values are compared the total path weight (links and nodes).