PBT Puts Nortel Back in Favor at BT

BT group Plc has added Nortel Networks Corp to its list of suppliers for its next-generation network, NGN, with plans to deploy its Provider Backbone Technology for Ethernet-based services.

The Canadian equipment vendor has a longstanding relationship with the UK incumbent, but was one of two high-profile omissions two years ago when BT published the supplier list for its NGN, called the 21st Century Network, or 21CN. The other was the much weaker Marconi, which immediately became an acquisition target and was shortly afterward bought by Ericsson, the company that beat it for a place on the 21CN list.

While Toronto-based Nortel did not face such a drastic fate, its absence from the list laid bare its ongoing problems in terms of its financial reporting and the stability of its senior management. Being accepted back into the fold by one of its most important customers and a bellwether in the telecoms industry is therefore of immense importance. It is a tick of approval from BT for the recovery process taking place under CEO Mike Zafirovski. “This is a strong endorsement from a Tier-1 player,” said Philippe Morin, president of Metro Ethernet networks at Nortel.

That Nortel has made it back to the top table with BT is in part due to the greater stability Zafirovski has brought to the company since joining Nortel early last year. However, according to Mervyn Kelly, director of EMEA Carrier Ethernet for Nortel, it is also thanks to the PBT technology developed by the company, with “significant input from BT.”

PBT makes a few key changes to Ethernet in order for it to operate as a carrier transport layer. The issues it seeks to address are fundamentally that, in the form in which it has prospered in the enterprise market, Ethernet has neither scalability nor a deterministic nature, which in turn means it lacks reliability and cannot support guaranteed SLA. In sector parlance, it is a best-efforts service.

The scale issue is that the physical limitation for the kind of segmented services required by telco customers is 4,095 VLANs via Q-in-Q technology, or VLAN tagging, which is fine for most enterprises, but no use at all in major carriers with customers running into the millions. The determinism question comes from the fact that there is no way of knowing which routes through a network that individual packets will take, in addition to which, packets without a known destination will be broadcast to all in what is referred to as the “Broadcast Unknown” feature. Again, this is not a problem in enterprise networks, but causes havoc in major carrier networks where only packets known to be generating revenue should be transmitted.

PBT overcomes these limitations, and lest it be accused of pushing proprietary technology, Nortel is pushing for standardization through the IEEE, whose next meeting is January 22-26 when it is due to begin its considerations. The degree of BT’s support for the technology, even prior to the formal announcement of Nortel’s inclusion on the 21CN list, could already be gauged by the fact that the presentation to the ITU of PBT technology, a sort of courtesy gesture to the carrier community called G.PBT, was made by the UK carrier rather than Nortel.

The applications for which Nortel is pushing PBT fall into two camps: in terms of support for residential and business services, it can be the transport for triple-play, internet access, and storage services such as remote backup; second, in the Metro aggregation arena, it can be used for DSL aggregation, wireless backhaul, and delivery of carrier IP VPNs.

The competing technologies Nortel has beaten to get onto the list include T-MPLS, a subset of the MPLS standard designed to deliver the scalability that Kelly argued is lacking in the Layer-2 VPN technology known as VPLS. The main proponents on that side are Alcatel and Cisco, each with their own specifics, but have in common that they seek to address the issue from Layer 3 where MPLS resides.

Other switching vendors like Extreme Networks are starting to edge closer to PBT support, a trend that BT’s move with Nortel should accelerate.