It's the news that the Provider Backbone Transport (PBT) camp had feared: BT Group plc is sidelining its former carrier Ethernet favorite and will focus its data services strategy on Multiprotocol Label Switching (MPLS).

According to a source with knowledge of BT's plans, PBT (or Provider Backbone Bridge – Traffic Engineering, as it's known in the standards world) doesn't have what it takes to meet BT's customers' requirements, so the carrier has decided to build its Ethernet services strategy around MPLS instead. (See A Guide to PBT/PBB-TE, PBT in the Spotlight, and PBT/PBB-TE Guide: Vendor Talk.)

Light Reading's source notes that PBT is not being kicked out of BT or consigned to the waste basket. "BT will carry on looking at what PBT can do. This isn't a 'No' to PBT."

But the source says BT's customers want "multipoint connectivity, and that's what MPLS does better. PBT has an edge in some point-to-point scenarios," and will still be used for some services such as data center connectivity, but "customers want a multipoint technology for content distribution and corporate VPNs, so BT is going with MPLS."

And that includes using MPLS for the mobile backhaul services BT has been selling to the U.K.'s wireless carriers. Previously, PBT had been stipulated as the underlying transport technology for at least one of the major multiyear deals. (See BT Sells PBT-Based Backhaul Service.)

BT's verdict will come as a particular blow to Nortel Networks Ltd., BT's main PBT ally and (planned) supplier of PBT-enabled Ethernet switches. Nortel, while trying to excite the carrier community at large about the merits of using PBT in point-to-point service scenarios, has also been pushing heavily the multipoint capabilities of PLSB (Provider Link State Bridging), an enhancement to PBT that provides control plane and multicasting capabilities. (See Nortel Preps New PBT Switch.)

BT confirmed to Light Reading in an emailed statement that MPLS best meets its immediate needs, but that PBT is still in play. "Next Generation Ethernet is at the heart of BT’s 21CN architecture and is a key service platform in its own right. BT remains interested in what PBT can deliver for the future and continue to actively access [sic] the role PBT may have in BT’s 21CN architecture."

News that PBT, which had previously underpinned the British carrier's next-generation network (NGN) Ethernet strategy, had fallen out of favor had leaked late last week, following a few months of seeming indecision at the carrier. (See BT's PBT D-Day and BT Still Coy on Ethernet.)

That indecision was clear at the recent Ethernet Expo event in London, where Light Reading learned of a new Ethernet ITT (invitation to tender) issued by BT that was more heavily weighted towards MPLS. Previously, BT had made presentations showing PBT deployed throughout its NGN, the now industry-famous 21CN. (See BT Reconsiders PBT Plans, BT Touts 21CN Progress, New Service, and PBT Stars at Ethernet Expo .)

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