This read-write enumeration, applying to HDLC protocol only, sets an inter-frame delay in milliseconds, such as 0.5 or 1.0 ms, inserted between frames transmitted on the port to accommodate DTE equipment that needs extra processing time at higher speeds. An administrator adds this delay specifically for connected equipment operating above 56 Kbps that requires breathing room between frames. For example, connecting an older DTE device that struggles at higher HDLC speeds might require selecting a nonzero frame delay to avoid it dropping frames.