Ethernet as a Carrier Service

No wonder Ethernet is popular. It’s easy to get along with. It talks to everything – Windows, Linux, Unix, Mac, FreeBSD. It’s simple to implement: just about anyone can sling together an Ethernet LAN and it will work, mostly.

Ethernet is technically forgiving. Sketch a LAN on the back of an envelope, plug it all together and it will usually work. Yet, certainly for a large network, the designer should understand the main sources of traffic and segment the network to optimize flows. But even if you don’t do that, the data will still get there. Thanks to Ethernet’s forgivingness, LAN designers do not, generally, need to calculate exact bandwidth requirements in every segment. LAN administrators in many companies don’t rely on complex management systems to tell them if there’s a capacity problem rather they respond to user complaints of network sluggishness and address the congestion problem by throwing more hardware at it. You can throw in some class-of-service prioritization and improve quality for VoIP and video simply by upgrading the switches. And bit-rate conversion comes built-in, unlike in traditional phone networks. There is no thought required: people routinely interconnect devices running at a variety of data rates over an Ethernet LAN.

As a result of Ethernet’s friendliness, every IT department in every enterprise depends on Ethernet. And due to its familiarity and ubiquity, costs of Ethernet switches and routers have steadily decreased; at the same time as performance and reliability have increased. Ethernet on the LAN is a success.

By contrast, ATM is hard work. ATM is a telco-oriented technology that was designed to do the same sort of job in the WAN as Ethernet does in the LAN, and at one time, ATM was the leading candidate for a unifying technology across WANs and LANs. In the world’s public telecommunications networks, ATM was a success. But no one now is seriously talking about ATM migrating into the LAN. It is not that ATM is an inferior technology. Far from it – it is versatile and full of features and it enables management of QoS for multiple types of traffic. But ATM is a complex technology and network architects and engineers need to know what they are doing with ATM to make it work well. As a highly specialist technology aimed at telcos, ATM hardware prices have not experienced the big cost reductions achieved by the deployment of Ethernet as a general purpose technology across millions of corporations, small businesses, and homes.

The success of Ethernet in the LAN led people to think about ways of realizing the same sort of benefits (especially low prices) in the wider network. They understood that if Ethernet could be used across cheap high-capacity fiber that could be privately owned, or rented, or shared (as a municipal or condominium network) then these links could be easily integrated with their enterprise networks. At the same time this approach would reduce reliance on traditional carriers.

The implications of this were not lost on strategists in telcos. If anyone could deploy Ethernet, and Ethernet was everywhere, and any content or application (including voice) could be delivered via IP over Ethernet, then what role would there be for the “common carrier.” If traditional telcos chose not to provide Ethernet-based services then they would eventually be marginalized. Add this to the potential of VoIP and IP in general for relegation of telcos to being simply bit-carriers and we realize that being a telco strategist must be a really interesting job these days.

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