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Ethernet takes a step towards service providers

Peter Judge ZDNet.co.uk

Published: 06 Mar 2003 15:34 GMT

The competition: RPR is still there

Metro Ethernet originally had competition from a specification called Resilient Packet Rings (RPR), which was defined within the IEEE as standard 802.17. Like Sonet, it uses a ring-based topology, but one which is optimised for data traffic. Chen politely says, "these technologies give carriers the option to choose whichever fits best into their needs," but many people see RPR as, at best, a niche standard.

RPR is not as scalable as Ethernet, and will not handle Ethernet traffic as easily as native Ethernet, causing more expense to service providers. It is based on pre-standard specifications from Cisco called Dynamic Packet Transport (DPT). It is intended to extend and replsce Sonet, but observers wonder why a service provider would replace its Sonet networks, when it can put in metro Ethernet alongside, and migrate the data traffic away from Sonet to Ethernet.

Surprisingly, even analysts who predict a big role for metro Ethernet still believe RPR will have a strong supporting role -- if only because it has adopted a more sensible strategy with respect to Sonet.

"Will RPR go away? Surprisingly and resoundingly no," said Howard. "A year ago I thought RPR was dead, but now it lives, and carriers want it. Carriers like rings!" RPR's saving grace, says Howard, emerged last summer: "It will be offered as a Layer 2 method to pack bursty packet traffic onto the world's existing Sonet and SDH rings." A recent Infonetics study of 20 North American service providers showed some 25 percent planning pre-standard (DPT) RPR and 19 percent planning to use the final 802.17 standard in their networks by the end of this year. Meanwhile, however, Ethernet is acquiring carrier class attributes. The MEF is working on making it better able to carry TDM traffic, so that it will ultimately be able to support voice. "With these capabilities, service providers can cap their existing networks, and grow a shiny new metro Ethernet, at much less cost and operational expense than Sonet and SDH based networks," says Howard.

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