
404 Networking Explained, Second Edition
lying somewhere between X.25 and ATM relative to their respective data transmission
rates. Frame relay data rates dovetailed nicely with the local loop—the link between a cus-
tomer’s site and the telco’s nearest point of presence (POP). SMDS and B-ISDN were ini-
tially designed to transmit data, fax, graphics, video, and voice at speeds from 45 Mbps to
155 Mbps. ATM was designed initially to offer the same kinds of services as SMDS and
B-ISDN, but its transmission rates were from 45 Mbps to 2.4 Gbps.
Much has changed in such a short period of time. In the United States, frame relay has
essentially pushed SMDS ...