Metro Ethernet Ain't Easy

Telecommunications magazine has an case study on Southern Light's experience with Metro Ethernet (over fiber):

While Ethernet is a core part of Southern Light’s metro services offering, Daniels holds no punches in saying Ethernet has been nothing but easy to deploy in a carrier network. “You know, Ethernet is the ugly sister that shouldn’t have made it to the prom, but she did,” he said. “Ethernet was not designed for metro transport [but with] creativity and lack of available resources, we, as an industry, have made it work.” At issue were a series of technical gremlins, particularly Spanning Tree Protocol (STP), which, while not necessarily an issue in the Ethernet-based LAN, were quite problematic in a Layer-2 carrier metro network. In fact, spanning tree issues were a major contributor to outages on its VoIP LEC (Local Exchange Carrier) customer’s networks. Traditionally, Southern Light used to run a Layer-2 network off two core switches to provide Ethernet services, but when that began to have issues, it switched to using Layer-2 switching off a single core switch. The operator has now found its savior in Provider Backbone Transport (PBT), a technology that enhances Ethernet transport with SONET-like deterministic qualities. [using Nortel MERS 8600s]