A Parallel MAC Architecture for a Gigabit/s DQDB MAN Suitable for Multimedia Applications

Medium access control protocols based on a dual bus topology, such as the IEEE 802.6 Distributed Queue Dual Bus (DQDB), are usually considered to be highly satisfactory for high speed networks. But the DQDB can only partly support new sophisticated multimedia services, mainly because the increase in the channel bit rate needed to meet the greater bandwidth requirements causes an increase in unfairness in the medium access control of the nodes. In this paper the authors propose a Gigabit/s Metropolitan Area Network (MAN) based on the IEEE 802.6 DQDB protocol and multichannel connectivity on optical fiber, by means of Wavelength Division Multiplexing (WDM). They present a parallel node architecture in which N DQDB subnodes parallelly access N WDM channels. Channel access at each node is regulated by N finite state machines operating independently and sharing a single MAC Convergence Functions (MCF) block for the segmentation and reassembly of user information. On the basis of the MAC architecture proposed, a network management structure is also presented, with particular reference to the Quality of Service monitoring processes. The proposed architecture is more modular than the DQDB standard; it provides greater fairness and better access delay and allows efficient management of service classes with priority.