The APPN Class of Service indicates the required characteristics of the nodes and lines in a route and the transmission priority of sessions. The possible line characteristics that can be specified include the security, speed (line capacity), propagation delay, and cost (both per unit of time and per byte). There are also three user-defined parameters that can be used to specify additional characteristics. The node characteristics that can be specified are the level of congestion allowed when selecting a node for routing and the desirability of the node for intermediate routing. The desirability of using a node for intermediate routing is called route resistance.

The characteristics are specified in ranges, with a low weight assigned to the most desirable set of ranges and a high weight assigned to the least desirable set of ranges. The first row in the default Class of Service has a very low weight and has the most restrictive set of ranges. The next set of ranges is less restrictive but has a higher weight. (These sets of ranges are called LINEROWs and NODEROWs.) The last set of ranges has the widest range of acceptable characteristics but has a very high weight. By coding the rows in this manner, the best resources (lowest weight and best characteristics) are chosen when determining the route.