Written by: Howard Green, Sylvain Monette, Jonathan Olsson, Panagiotis Saltsidis and Attila Takács

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This article reviews the developments and emerging standards of native Ethernet technology that give Ethernet the features of a packet transport technology for public networks. The increasing dominance of IP and Ethernet is enabling a convergence of networks and allowing for a wide range of services (to business and residential customers and for mobile backhaul) to be carried over the same infrastructure.

Introduction
IP and Ethernet are becoming ubiquitous - IP packets make up the majority of traffic carried over the world's communication networks (by volume, if not yet by value) and more often than not this traffic is presented to the network in Ethernet frames. In short, Ethernet is increasingly becoming the bearer technology of converging networks.

The advantage of Ethernet has always been its ability to leverage high volumes, thanks especially to its dominance in the enterprise market. Throughout its thirty-year history, Ethernet has shown an extraordinary capacity to adapt and grow. It is popular largely because of its ability to self-configure, based on the key concepts of

• learning bridge" (flooding and associating learned destination addresses with bridge ports); and
• spanning tree" (the protocol used to avoid loops).

Despite this, these features have weaknesses in the context of large-scale public networks. The learning bridge procedure, for example, broadcasts unknown addresses, resulting in flooding, which clearly does not scale well. Similarly, the spanning tree protocol often makes poor use of underlying transport resources. Moreover, standard Ethernet lacks key public network features, in particular for operation, administration and maintenance (OAM) and for isolating customers.

Public networks are evolving into what Ericsson terms Full Service Broadband, which carries a steadily widening range of rich multimedia services to fixed and mobile devices over a common network with carrier-class characteristics, such as scalability, robustness, and resilience.1 Current developments in Ethernet as a public network transport technology include

• the definition of standardized services to be provided by an Ethernet-based public network;
• flexibility, to enable scaling a network to a global size while supporting many concurrent service networks;
• comprehensive OAM mechanisms for monitoring service quality and service level agreements (SLA), and for detecting and locating faults and misconfigurations; and
• the creation of a highly scalable transport control plane solution that facilitates rapid restoration of service and supports automated provisioning.

Several technologies including generic framing procedure/synchronous digital hierarchy (GFP/SDH) or multiprotocol label switching (MPLS) can be used to transport carrier-grade Ethernet services. The focus of this article, however, is on the evolution of native Ethernet technology to carry these services.