By Serge-Paul Carrasco on March 30, 2007

The Versatility of Ethernet

(T) With 100 Gb Ethernet coming soon, Ethernet, by all means, is a versatile technology. It can be deployed in many applications over many data rates. But, we need to distinguish Ethernet as a service and as a transport; Ethernet for residential and businesses; Ethernet in North America and Ethernet in Europe and Asia.

First, Ethernet target market is mostly businesses

Residential customers just want a cheap convenient high-speed Internet access.

Second, Ethernet as a transport technology is getting traction by incumbent service providers

It took about 10 years for SONET/SDH to be standardized. And, SONET/SDH products have been deployed since the early 90s. Resilient Packet Ring (RPR) or IEEE 802.17 was technically a wonderful technology because of its bandwidth multiplication capability but failed because of a lack of greenfield opportunity investments.

The Metro Ethernet Forum (MEF) has made in the past a number of initiatives to make Ethernet “carrier-grade” such as protection switching with MPLS FRR, OAM management (like ATM F4/F5), QoS, and even CES/TDM support…Those initiatives sparked the adoption of Ethernet as a transport technology.

Third, Ethernet as a service

Every business wants an Ethernet interface as a service instead of DS1/DS3/OC-n. And, Ethernet as a service is cannibalizing service providers’ legacy leased lines and Frame Relay revenues. So, the difficult question is how economically service providers can provide Ethernet services.

Ethernet Service over Fiber/SONET

In North America, Service Providers were initially very clear: Ethernet must be delivered through the existing fiber and SONET infrastructure. Ethernet has been initially provided mostly so far with Ethernet switches (sometimes a router) connected to an Ethernet port of an MSPP (SONET ADM with data capability). Those solutions are started to be replaced as we speak by micro-MSPPs that offer Ethernet over a SONET CPE. In particular, with GFP/VCAT/LCAS, SONET is becoming much more efficient to transport Ethernet and IP.

For a specific area, some service providers (such as Verizon) had as well provided in the past Ethernet as a simple Layer 1 point connection with media converters over existing fiber layouts. Same story with service providers trying to deliver now Ethernet over broadband, Ethernet over copper and, Ethernet over PON…

Ethernet Service from an IP/MPLS Router

So besides Ethernet over SONET, service providers are offering more and more Ethernet through an IP/MPLS routing or an Ethernet switching infrastructure.

Large enterprises have been quick to adopt IP VPNs with BGP/MPLS. But a lot of service providers’ business model is to provide commodity “bandwidth”, pure Layer 2 services. So definitely, there is a fair opportunity to provide Ethernet services through Virtual Private LAN Services (VPLS), a trend that was started in early 2002/2003 by TiMetra (now Alcatel), Riverstone and Vivace (now Tellabs), companies that developed the first generation of ASICs to support the MAC learning/aging functions of VPLS. VPLS is a “brilliant” engineering technology. However, the challenge about VPLS is that it is using basically an Ethernet learning bridge model through MPLS. And, we have learned 10 to 15 years ago that bridging does not scale that the reason why routing was invented. The addition of H-VPLS by Tenor Networks (now a company that does not exist anymore) attempts to solve the scalability issues of the VPLS bridge model.

Ethernet Service from an Ethernet Switch

The market for service provider Ethernet switches has been so far mostly in Asia and in Europe and had very little traction in North America (because of North America SONET’s legacy). The major players that can provide a carrier-grade switch are Cisco, Nortel, Foundry, Atrica, Tellabs and Extreme.

The Rapid Technology Evolution of Metro Ethernet

A number of initiatives both on MPLS and on Ethernet/VLANs are trying to improve the present state of the Ethernet transport technology.

The ITU-T is defining T-MPLS which is a subset of MPLS encapsulation for point-to-point transport with MPLS OAM as defined in Y.1711/Y.1731. And, various switch vendors are working on various ways to creatively use VLANs tags. First, Q-in-Q/vMAN or IEEE 802.1ad, called Provider Bridge (PB), provides a way to assign VLANs to multiple customers and stack them over the same connection. Second, Mac-in-Mac or IEEE 802.1ah, called Provider Backbone Bridging (PBB), improves the scalability of Q-in-Q limited to 4,096 VLAN tags through the use of a VLAN provider tag (very similar mechanisms to VPLS).

So as Ethernet is more adopted as a transport technology, more and more of those efforts will succeed in the soon future.

Carrier-Grade Ethernet Versus Enterprise Ethernet

Enterprise Ethernet switching markets and requirements are quite different from carrier-grade Ethernet switching. The market is a healthy $14 B market worldwide where Cisco is making around $10 B. But the requirements are now driven by the integration of wireless LANs (802.11), security built into the switch and facilitating the deployment of VoIP applications.

But obviously, there is a lot of technology synergy between Enterprise and Carrier Ethernet switching.

Definitely, Ethernet is Versatile

It can be used both for enterprises and service providers. And, for service providers, it is now both a service for their customers and a transport system. And, with 100 Gb Ethernet coming soon, Ethernet has still a long life ahead.

Categories: Networking