Carrier Ethernet Gets a Boost

Richard Chirgwin explains how advances in Carrier Ethernet will trickle down into better, faster WANs.

Layer 2 versus Layer 3 is an old us-versus-them battle that's been with us as long as IP.

It revolves around whether you should build your WAN using a lower-layer protocol (Layer 2), and keep track of your own inter-office routing, or build your WAN using IP (Layer 3), and hand off inter-office communications to the carrier.

For much of the 1990s, the Layer 3 camp has been in the ascendant, partly because IP became ubiquitous and cheap, partly because Layer 2 services such as Frame Relay and ATM were relatively expensive (because of the low-volume specialist switching equipment involved) and complex, and partly because handing routing off to a carrier relieved IT departments of the need to manage their own IP routing schemes.

However, even as ATM and Frame Relay continue their slow decline, Ethernet has become the technology of choice for Layer 2 advocates - and it's carrier Ethernet that Extreme Networks is pursuing with this weeks' launch of a new range of high-capacity, high-port-density, high-speed switches.

Targeted at carriers, the Extreme Black Diamond 20808 series of switches offers plenty of big numbers: each line card can run 64 10 Gbps Ethernet ports, and can handle 120 Gbps of customer traffic. Each rack of 20808s can run up to 192 10 Gbps Ethernet ports - which translates into lots of customer ports, given that most Ethernet customers in Australia are currently at 10 Mbps or below.

And, the company says, all of this is offered at a lower per-port price than carrier products from its competitors - Alcatel, Juniper and Cisco.

So what does this mean for TechTarget ANZ readers - given that you're not in the market for a carrier switch?

The ongoing development of carrier Ethernet switching is going to be reflected in faster, more affordable, and more transparent Ethernet-based WAN services.

As Craig Adams, Extreme's director of solutions marketing, told TechTarget ANZ, Ethernet-based carrier services are now based on platforms that reflect the characteristics that made old-fashioned Layer 2 services so expensive.

For example, Adams said, the vendor has put a lot of effort into what it calls "hitless failover". By separating the management modules from switching modules, products like the 20808 allow carriers to move customers between switches without service interruption (something which has barely reached the DSL world at this point).

"If you need to move the switch, you can take the services from it, onto another switch, power down, and reprovision the services without interruption to the end user, because provisioning and control happen independently of the switching.

"There's also redundancy in the management modules, and in the [switching modules] separately from the management modules."

The View from the End User 

The point of the muscle, the density and the redundancy is that carrier-based Ethernet is becoming a serious end-user service, offering a platform for carriers to build simple, fast and price-competitive Layer 2 services.

Adams says the take-off of carrier Ethernet is the result of work in the Metro Ethernet Forum (MEF). In particular, he said, the definition of "E-line" services (and their implementation in switching equipment) has changed the landscape of Layer 2 services.

(E-line is a point-to-point Ethernet customer service based on an "Ethernet Virtual Circuit", in which the carrier manages the speed offered to the customer's offices.)

"When E-line was defined, customers could begin to directly compare different Ethernet services - an E-line service in New York is comparable to the same service in Sydney.

"The MEF is making Ethernet very easy to buy."

This addresses one of the key advantages IP-based services have over Layer 2 services: everywhere you go, an Internet service (or a private IP service) looks much the same - the difference is in speed and downloads.

And, Adams said, Layer 2 services have other advantages.

"The biggest thing is that customers understand Etherent inside the firewall. Everything - the data centre, all the applications, the voice and the wireless, all run over Ethernet, and people understand it."

And the Ethernet pitch doesn't get in the way of customers' use of IP for data, voice and video - because the WAN service is invisible to the upper layer. Likewise, the customer network remains invisible to the carrier.

"As an enterprise customer, I don't want the carrier knowing all of my MAC (Media Access Control) addresses and all of my end points. I want to drop my traffic at one end, and it appears at the other end, and I take care of it," he said.

Adams says the Extreme 20808 switch is designed to support multiple services - voice, streaming video - with hardware-based QoS and support for multicast streams.

Read more on WAN performance and optimisation

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