Nortel to Provide PBT-based Ethernet for BT’s 21CN

BT revealed Monday that Nortel will provide Ethernet gear – including Provider Backbone Transport (PBT) technology – for the carrier’s 21st Century Network (21CN). The move was expected, given BT has been driving Nortel’s PBT strategy and the companies have done joint presentations on the technology.

The value of the deal, which includes Nortel's Metro Ethernet Routing Switch 8600 and Metro Ethernet Services Unit 1850, was not disclosed.

PBT, which to date has been championed exclusively by BT and Nortel, is a technology aimed at better positioning Ethernet to function in transport networks, the companies said.

It “provides a means of traffic engineering the network so paths through the Ethernet cloud can be preconfigured (similarly, protection paths can be pre-configured). The result is predicable, resilient behavior from a packet network that is based on Ethernet only and therefore enjoys similar cost advantages,” John Hawkins, senior marketing manager for carrier Ethernet at Nortel, explained during a recent interview with xchange. The need for spanning tree protocol thus goes away for those engineered paths, and the network becomes more well-behaved and predictable, according to a Nortel White Paper.

However, some say the push for PBT is just an attempt by Nortel to create a position for itself in the carrier Ethernet space as it tries to play catch up. Some, like Atrica Inc. and Juniper, also argue that PBT is not needed because existing carrier Ethernet and MPLS products already more than adequately address the requirements of transport networks.

Juniper Fellow Kireeti Kompella said there are no features in PBT that aren’t already in MPLS, yet noted that PBT requires a whole new control plane and data plane, plus it doesn’t include the fast reroute function found in MPLS. “PBT is what MPLS did 10 years ago,” Kompella continued. “PBT is trying to redo all kinds of standards like pseudowire, Layer 2 and 3 VPNs, etc.”

Despite the gains PBT has made with BT, how widely the technology will be embraced is a big question mark. That’s at least in part because PBT is still very early in the standards process; an IEEE 802 study group has just recently begun looking at PBT. However, Hawkins said the technology won’t require much change beyond what is already adopted for 802.1ah (Mac-in-Mac or PBB).

It should also be mentioned that another technology, T-MPLS, aims to do pretty much what PBT promises to do.

T-MPLS (the T is for transport) is a subset of MPLS specifically designed for transport applications. The idea here is to simplify MPLS from an OAM&P standpoint, explained Mike O’Malley, group manager of portfolio marketing at Tellabs.

Tellabs was among the companies that initiated work on T-MPLS within the ITU back in May 2005. However, it’s Alcatel that is generally considered the key proponent of T-MPLS. But Alcatel declined to be interviewed for this article. Alcatel spokeswoman Tracy Dupree indicated to xchange in December that the company was reviewing its strategy in light of the merger with Lucent.

Although T-MPLS has made strides on the standards front at the behest of several important vendors, no service providers have yet publicly endorsed T-MPLS. However, O’Malley said there’s a lot of interest in T-MPLS from services providers, but he added that Tellabs is also looking into PBT and has no preference for how the market goes on this one.

Architecture approval for T-MPLS – which is further along than PBT on the standards track – was granted within the ITU in November 2006, so the first set of recommendations for this technology is complete. Additional work on OAM extensions for T-MPLS is ongoing and is targeted for consent in June, according to Tellabs’ spokeswoman Ariana Nikitas.

“If you look at the full list of MPLS commands – label swapping, all of those things – there are a lot of things that are in MPLS that are meant for router updates and things like that that don’t pertain to transport equipment,” said Tellabs’ O’Malley. “The idea behind T-MPLS is to use that goodness of MPLS from an end-to-end management and traffic engineering standpoint to manage multiple pipes of transport equipment similarly, but to do it with a reduced command set.”

But, as with PBT, companies like Atrica and Juniper don’t see the need for T-MPLS.

Juniper’s Kompella said T-MPLS is positioned as a way to make MPLS more palatable to telcos, who are more comfortable with connection-oriented networking. “Just speaking with an IP-centric language scares a lot of people,” he said. But MPLS can be connection oriented, using RSVP, or it can be connectionless, via LDP, Kompella added. The funny thing about the effort to make MPLS more connection-oriented, he continued, is that most service providers using MPLS in their networks are using LDP, so this T-MPLS effort “goes against the grain of what people are actually doing in their networks.”

BT www.bt.com  

Nortel www.nortel.com

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