There are several problems in the NJI interface between RSCS V1.3 and V2.1. Anyone running such a link should check for fixes to BOTH systems. With V2 IBM started to actually implement some of the things in the Protocol Manual (GG22-9373-02 or later)! (For example, RSCS V2 now actually uses the 'hold at destination' bit, etc.). There have been problems with spanned header records not being handled right. I vaguely remember seeing some apars for the '1 second message delay' (they now pass null records back and forth each second when the line is idle). We were getting "BCB Threshold Errors" (VM26766 against V1R3). In looking at the traces level 2 thought they saw several other errors having to do with error recovery.