PBT = Provider Backbone Transport. Developed by Nortel Networks and being STRONGLY backed by the BT Group (a european carrier). The "official" defenition is as follows:
PBT is a management platform that strips out some of the management complexity of Ethernet for the delivery of point-to-point Ethernet services.
Basically, they want to simplifiy Ethernet. No spanning tree, flooding, and all those other features that carriers will never use. I guess it's easier to manage service delivery without all these added features. Nortel claims this approach gives carriers the control and scaleability they want from their Ethernet network without having to resort to MPLS which can be quite expensive. The technology is praised for being standards-based, scaleable, secure, resiliant, providing OAM (operations administration and maintenance), fault-finding, and having TE by default (one of the big pluses of MPLS).
BT quotes:
"There are inherent limitations in the way the Ethernet protocol works that limit the scaleability on the wide-area network". "Things like self-discovery [and] broadcast packets work well in an enterprise, [but once you] start to have many, many thousand end points or a big-scale network, some of those things start to run out of steam effectively."
"So we proposed this idea that the standards world calls 'provider backbone transport,' which is a way of reducing and removing those limits, but still trying to keep the inherently low-cost nature of the Ethernet hardware, which is why we would like to use it."
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