The pacing window size between two endpoints of a pacing stage is constant when fixed session-level pacing is being used. The window size is passed in the BIND request during session activation. The window size in the BIND response is the actual window size used. The number of pacing stages can be the same for both directions (primary-secondary and secondary-primary) in a session, or it can be different. In Figure 1, APPL1 is in session with a type 2.0 node. Two-stage pacing occurs from APPL1 (primary logical unit) to the type 2.0 node (secondary logical unit), and one-stage pacing occurs from the secondary logical unit to APPL1. In this case, the NCP provides the boundary function for the LU.

Figure 1. Fixed-session pacing (one- and two-stage)