AT&T MAN Architecture and Services

The AT&T proposed MAN architecture, which was approved for standardization by IEEE 802.6 Committee on Metropolitan Area Network standards, is a hybrid two level switching hierarchy in which distributed switching is used at the lower level and centralized switching at the upper. Centralized and distributed switching have previously been discussed as distinct alternatives. The AT&T MAN architecture merges the two approaches of distributed and centralized switching into a single, integrated architecture, preserving the advantages of both and offering a graceful evolution towards the anticipated Broadband ISDN networks. The central switch provides fast interconnectivity between networks, removes the bandwidth limitations of shared medium architectures, and ensures security. The shared medium approach efficiently utilizes the available bandwidth, provides mechanisms for congestion control, supports broadcast/multicast services, and reduces the load offered to the central switch.