The Frame Relay header includes three single-bit flags that Frame Relay can use to help control what occurs inside the Frame Relay cloud.  These bits can be particularly useful when one or more sites use an access rate – the clock rate of the access link – that far exceeds the CIR of a VC.  If a router has a T1 Frame Relay access link, but only a 128-kbps committed information rate (CIR) on a VC that goes over that link, the router can send a lot more data in the Frame Relay network than the business contract with the Frame Relay provider allows.