Media Coverage

PBB-TE Ups Ante on Ethernet Transport

By Sean Buckley

If there’s anything to glean from the recent announcement that BT will deploy Siemens and Nortel Ethernet equipment in its 21CN network, besides being another win for Ethernet, it’s proof that carriers are seeing value in the emerging IEEE standard for Ethernet transport, PBB-TE (Provider Backbone Bridging-Traffic Engineering).

PBB-TE, which provides enhancements to Ethernet known as PBT (Provider backbone transport), can bring control to data paths within a large carrier network, enabling QoS and the ability to set aside specific paths for specific traffic types.

PBT can bring the connection-oriented characteristics and deterministic behavior that carriers have grown accustomed to in legacy technologies such as SONET/SDH to Ethernet. PBT achieves this by disabling the concept of flooding/broadcasting and Spanning Tree Protocol, which enables it to act like a traditional carrier transport technology.

BT, which will utilize the Nortel and Siemens Ethernet platforms to transport its residential and business service traffic, sees that the implementation of PBT will complement its 21CN MPLS strategy.

“The basic advantage of PBT is cost,” said Michael Howard, principal analyst for Infonetics. “If you can keep all of the transport at Layer 2, you have to have Ethernet switches; you don’t have to buy routers. PBT allows you to build a total Layer 2 transport network with no routing. I think that and the operational simplicity are the benefits of PBT vs. using MPLS.”

While BT has been the foremost supporter of PBB-TE and PBT, industry sources say that both Bell Canada and Verizon are in favor of the PBB-TE.

On the vendor side, the PBT/PBB-TE drive is coming from two angles: traditional optical vendors and Ethernet switching vendors.

Along with Nortel—one of the most vocal proponents of PBB-TE—Cisco, Meriton Networks, Siemens and World Wide Packets have marshaled support for the emerging standard.

Traditionally a provider of optical networking equipment, Meriton Networks, for one, has developed a product upgrade roadmap for Carrier Ethernet transport by enhancing its existing 7200 OSP. Meriton Networks’ two-phase strategy will enable carriers to support GigE networks via sub-wavelength switching and grooming of nine GigE streams and integrating Ethernet gateway tunnels (i.e., PBB-TE and T-MPLS with intelligent WDM).

“Carrier Ethernet transport is a very clean interface between the service layer and the transport layer,” said Bill Gartner, Meriton’s COO. “As an Ethernet handoff between those two layers, the service layer can do its job, which is to manage the services and not have to have specific knowledge about the transport layer. It needs to know that it can get a service between points A and Z, and the transport layer can provide that capability."Still, for all the momentum around PBB-TE, not everyone is on board.

Alcatel-Lucent, for one, argues that the T-MPLS (transport-MPLS) approach, which provides simplified OAM&P processes, is farther along in the standards process, while the PBB-TE movement is just getting started.

Despite that obstacle, Mick Reeve, an independent consultant and former chief architect on BT’s 21 CN, says that the PBB-TE group can leverage similar elements adopted by the T-MPLS group.

“The other area where T-MPLS is slightly ahead is the way that different sorts of services are mapped into MPLS, such as ATM, FR and Ethernet, but I think PBT can reuse that stuff,” Reeve said.