Transporting Ethernet services in metropolitan area networks (MANS)

In many big cities in the industrialized world, large dedicated data transport networks (the MANs, metropolitan area networks) have been deployed in the last few years to provide cheap broadband Internet access to citizens, as well as broadband interconnections between different branches of a business company. The current MANs are based, in the backbone side, on legacy TDM (time division multiplexing) techniques, like SONET (synchronous optical network) and SDH (synchronous digital hierarchy). The enormous diffusion of the Ethernet technology (wired 8023 or wireless 802.11) in the LAN environments and the availability of Ethernet interfaces with a very low cost has almost forced telecom operators to consider it as the only possible MAN access technology to sell Internet access services to the large public and business. The MPLS protocol has been chosen by the metro Ethernet forum (MEF) to adapt Ethernet traffic to the SONET/SDH networks. This article aims to characterize the behaviour of the different solutions for transporting Ethernet services in the MANs, with or without MPLS support, in terms of efficiency, delay, traffic Engineering capability, fault tolerance, scalability, cost and complexity.