Nortel will enhance a proprietary technology for improving the performance of Ethernet as part of its emphasis on becoming a leading supplier of metro Ethernet systems for carriers.

Nortel will be adding link state protocols and synchronization to Provider Backbone Transport (PBT), a Nortel-developed derivative of the Ethernet standard intended to bring connection-oriented characteristics and deterministic behavior to Ethernet. PBT turns off Ethernet's Spanning Tree and MAC address flooding and learning characteristics to enable Ethernet to behave more like a traditional carrier transport technology.

Nortel recently announced a strategic plan to focus on metro Ethernet as one of the key market drivers for the company's future growth. Market tracker Infonetics Research predicts the Ethernet services market will reach $22 billion in 2009 from $2.5 billion in 2004.

The addition of link state protocols to PBT will enable carriers to configure Layer 3 topologies within their metro Ethernet/PBT network, said John Roese, Nortel CTO during an interview last week at the company’s Ottawa labs. A Layer 3 topology will make the Ethernet network look and behave more like an OSPF or IS-IS router network, in which each router broadcasts or multicasts information on the cost of reaching each of its neighbor nodes.

This is what carriers prefer, according to Roese, adding that it will also facilitate multipath trunking. Multipath trunking allows operators to configure multiple links between switches and servers instead of traditional point-to-point trunks, which in turn enables network configurations for optimal traffic handling and load balancing.

"We've realized that the topology requirements of the carrier are much more sophisticated: they like the idea of Layer 3 topologies because it gives you the ability to have multipath, and more intelligent multipath," Roese said. "While you could try to use things like (IEEE) 802.1s and multiple Spanning Trees, that's not really desired by the carrier to be running Spanning Tree across their network."

Link-state PBT is in Nortel's labs. It is unclear when it will emerge in PBT-enabled products, which currently includes Nortel's Metro Ethernet Routing Switch 8600 and next year the Optical Multiservice Edge 6500 provisioning platform.