BT Cools on PBT for Carrier Ethernet Transport

Carrier Settles with MPLS for Current Carrier Ethernet Needs

PBT, and the corresponding standard effort known as PBB-TE, have lost some luster recently. BT, which had been one of the biggest boosters of PBT for Carrier Ethernet transport, today told xchange it will be using MPLS, as opposed to PBT, for the immediate future. Meanwhile, Verizon told xchange in April that it doesn’t currently see a need for PBT for Carrier Ethernet transport.

PBT, whose key early promoters were been BT and Nortel, has been positioned as a way to make Carrier Ethernet more deterministic and to bring it into transport networks without what some perceive as the high cost and complexity of MPLS. Meanwhile, other players in the communications field have been emphasizing that MPLS, and related technologies like VPLS, address the Carrier Ethernet transport issue just fine, thank you very much.

Responding to a recent report that it had dropped plans to deploy PBT, Wendy Sycamore, pr manager for BT Group Chief Technology Office, told xchange: “Next-generation Ethernet is at the heart of BT’s 21CN architecture and is a key service platform in its own right. Following a comprehensive internal review of the relative merits of PBB-TE and MPLS against our immediate customer requirements, BT has decided to focus its attention on MPLS.

“Our customers’ needs today are primarily for connectivity for applications like content distribution and corporate VPN services across multiple locations,” she continued. “These applications are best met today by MPLS.”

But Sycamore also stressed that BT remains interested in what PBT can deliver for the future and will continue to actively assess the role PBT may have in BT’s 21CN architecture and related to Carrier Ethernet.

As for Verizon, Nick Del Regno, principle member of technical staff at Verizon Business, this spring told xchange: “Currently we don’t really see a need for PBT, and we don’t have any plans to deploy PBT.”

However, he said Verizon Business does have some interest in PBB relative to Carrier Ethernet.

“The problem, and it’s really Nortel’s position in the market, is that they tied PBT and PBB together,” Del Regno continued. “We see benefits, we see merit in PBB, both within our traditional native Ethernet networks that are LATA-bound, so they’re fairly geographically constrained. As well, PBB may be a good tool to scale national and global VPLS networks.

“PBT, on the other hand, it’s kind of a step backwards,” he added. “When we first looked at deploying Ethernet services, we did something very similar, but we did it with VLAN; it’s a nailed-up, hop-by-hop VLAN cross-connect, very similar to how frame relay was originally deployed and how ATM was deployed without PNNI. PBT is a lot like that same type of approach, and with the promise that we might someday make it a control plane, and that ‘oh, by the way, that control plane is probably going to be GMPLS.’”

Manu Kaycee, vice president of product technology and strategy at Telco Systems, said VPLS is a better approach than PBT to address Carrier Ethernet transport.

“[VPLS] is a hardened technology which has been proven for a number of years in existing deployments with large carriers worldwide, and it provides an extremely scalable way to provide Carrier Ethernet services on a worldwide basis,” Kaycee recently told xchange.

“The main attributes that are required by the [Carrier Ethernet service provider] customers are Layer 2 transparent services and the option to provide Layer 3 services -- security, scalability and fault tolerance,” continued Kaycee. “These are the five main attributes, and VPLS provides all these five based upon a proven technology.”

Kaycee said early MPLS implementations were expensive because they were based on retrofitted ATM switches, but that in recent years the vendor community has turned out purpose-built solutions optimized for VPLS.

“One of the things people have done to scale VPLS is called H-VPLS, or hierarchical VPLS. So, with hierarchical VPLS at customer premises you have [what is] much like the frame relay hub-and-spoke model,” said Kaycee of Telco Systems, whose eBook on Carrier Ethernet and VPLS is available here.

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