Ethernet Tackles Access, Aggregation And Transport
By Kamran Sistanizadeh
Published April 2007; Posted August 2007



Which does a better job replacing SONET/SDH rings in the metro: Ethernet or MPLS?

Throughout the evolution of local and wide area networks, enterprise customers have been exposed to a variety of service interfaces at different OSI layers—xWDM (wave division multiplexing) at Layer 1, SONET and Ethernet at Layer 2, MPLS at Layer 2.5, and of course, the ubiquitous IP at Layer 3. Each of these interfaces can be appropriate, depending on the customer’s application environment, the connectivity requirements among various sites and the need for more or less signaling, control and SLA (service level agreement) management.

Since customer premises networking environments are primarily built on Ethernet LANs, it would be highly desirable for carriers and service providers to find a proper combination of access and transport technologies optimized for transporting Ethernet among geographically dispersed LANs—within either the customers’ intranet or extranet service domains. Service providers and carriers require platforms in some parts of their networks that are optimized for Ethernet access, and in some parts of their network they need platforms that are optimized for Ethernet transport.

The evolution of Ethernet from the LAN into the access network (e.g., metro environment) began in earnest in 1999 after standardized Gigabit Ethernet technology interfaces on switches and routers became readily available. However, carriers had been deploying SONET since the mid 1980s, for their inter-office and regional transport backbones, so SONET was the more frequent choice in the metro. For long haul and for backbones in the core, SONET, ATM (asynchronous transfer mode), and frame relay ruled until the late 1990s, when MPLS began to attract more attention from carrier network planners.

Today, Ethernet’s proliferation in the LAN environment, and its ongoing speed advancements (e.g., 10-Gbps, and soon 40-Gbps/100-Gbps), have carriers contemplating Ethernet as the technology of choice for replacing SONET and MPLS. Recent initiatives in the IEEE, IETF and ITU are making changes to Ethernet aimed at pushing it from the access network into the transport backbone environment while also providing the operational and network management strengths and features of SONET/SDH. Ethernet is also being adopted as an “aggregation” and “backhaul” technology of choice by carriers for consumer broadband services and cellular data.



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About the author:

Dr. Kamran Sistanizadeh is cofounder and CTO with Yipes Enterprise Services, Inc., a provider of managed Ethernet services. He has been a leading contributor to various industry Forums (ANSI-T1, ADSL and MEF) and an ardent advocate of Ethernet services for enterprises.


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