This indicates whether the PDSN, Packet Data Serving Node, system supports call admission control for a given CDMA data session, with true meaning CAC is applied and false meaning it is not. Call admission control is what decides whether a new session gets admitted based on available capacity, so on a PDSN nearing its session-capacity limit, having this enabled specifically prevents oversubscription that would otherwise degrade service for all connected mobile data users rather than cleanly rejecting excess new sessions. A PDSN nearing peak capacity during a regional event with high mobile data demand would rely on this being set to true so new sessions get rejected once capacity limits are reached, rather than degrading service for everyone already connected.