This ITU-T Recommendation specifies the requirements on how to map ATM on a "circuit-mode connection" supporting unrestricted information transfer rates at integer multiples of 64 kbit/s up to the maximum rate of the interface (ITU-T Recommendation 1.231.10 [1]). The physical interface may typically be DS1 or EI (or any other physical interface). The specification shall apply for any N * 64 kbit/s rate up to 1920 kbit/s (N = 30) and be independent of type of interface (UNI or NNI).