Verizon Communications Inc. (NYSE: VZ) has chosen Nortel Networks Ltd. ’s Metro Ethernet Routing Switch 8600 to provide Provider Backbone Bridge (PBB) technology in its metro Ethernet backbone. As Light Reading reported last week, Verizon has been eyeing PBB technology for its metro network but, until now, had not made a formal decision.

Nortel regards PBB as a natural first step towards eventually implementing Provider Backbone Transport (PBT). But when asked if it regarded this win with Verizon as an eventual PBT win, Nortel couldn’t say.

“For us, this is just a confirmation that ultimately the best way to manage Ethernet growth is to use PBB over MPLS,” said Phillip Morin, Nortel's president of metro Ethernet networks.

PBB is a technology that addresses the scaling limitations of MPLS but keeps the operating simplicity of Ethernet. PBT, which is being standardized as PBB-TE, is a more sophisticated form of PBB that adds traffic engineering capabilities. (See A Guide to PBT/PBB-TE.)

Verizon has reportedly decided against PBT, instead using PBB in the metro and VPLS in the core. (See Verizon Also Shunning PBT.)

But not everyone is convinced Verizon has completely written off PBT. "This announcement certainly wouldn't indicate it, but I'm still not convinced that Verizon has shunned PBT altogether," says Sterling Perrin, senior analyst with Heavy Reading.

Verizon won't have trouble finding PBT if it wants it. In addition to Nortel's support, there's the Fujitsu Network Communications Inc. Flashwave 9500, which recently added PBT. While it's never been officially announced by Verizon, it is widely believed that Flashwave is the carrier's packet optical gear of choice. (See Fujitsu Supports PBB-TE, Report: Fujitsu Wins Verizon RFP, and Verizon Preps God Box RFP.)

Fujitsu would not comment on any prospective customer wins for the Flashwave 9500.

In the meantime, Verizon will be using the MERS 8600 for PBB and Multiprotocol Label Switching (MPLS). Nortel is not viewing this as any sort of concession that MPLS is a superior technology to PBB or PBT.

“We all know that MPLS cores have been widely deployed in the industry,” says Morin. “For us not to acknowledge that and not interoperate with it would be foolish. The good news is that they could’ve picked MPLS in the metro, but decided PBB was the right way for them to go forward, especially when the biggest challenge they have is scale.”Verizon's main technology in its core network is VPLS. But VPLS has scaling issues in the metro that have become a problem in larger cities like New York and Washington. Verizon is looking to front-end VPLS with PBB to address those scaling issues.

This is something Nortel and Verizon have been collaborating on for some time, according to Mike Loomis, director of carrier Ethernet sales for Nortel. "We've worked extensively with Verizon on Layer 2," Loomis says.

With Verizon now officially on board for PBB, Nortel is still looking for that big Tier 1 customer for PBT, since BT Group plc (NYSE: BT; London: BTA) appears to be favoring MPLS. (See PBT Sidelined at BT and Nortel: There's More to PBT Than BT.)

— Raymond McConville, Reporter, Light Reading