Nortel adds muscle, multicasting to PBT

Nortel Networks has updated its metro Ethernet portfolio with new hardware and software to add muscle to its Provider Backbone Transport (PBT) platform and give it the ability to manage multicast traffic.

A new internally developed processor lends increased scale to Nortel’s 8600 Metro Ethernet Routing Switch, allowing it to provision more PBT trunks and widen the message-processing bottleneck. The new processor, due in next year’s first quarter, doubles the 8600’s capacity from 30,000 virtual private networks per chassis to 60,000 (with 2 chassis per 7-foot rack). The updated gear can handle up to 12,000 pairs of PBT tunnels per chassis (a tunnel and a backup tunnel), while the previous release could handle up to 8000. New line cards based on the new processor can handle up to 1,000 customer MAC addresses each, giving the 8600 the ability to handle up to 480,000 subscribers per chassis.

“Your mileage may vary,” said John Hawkins, Nortel’s carrier Ethernet marketing manager. For example, if each tunnel is given 50 millisecond protection, the maximum may be less than 12,000 pairs.

One of the new line cards included in the new release includes E-Tree functionality, adding a point-to-multipoint option to traditionally point-to-point PBT. The E-Tree function suits the 8600’s PBT side for multicast video delivery, an application for which Nortel previously recommended using Provider Backbone Bridging line cards in the same chassis.

Nortel still recommends using regular PBT to create redundant backup connections between the hubs where video services are created. Closer to subscribers, the 8600 can now use service identifiers--or “virtual local area network instances”--that Nortel calls iSIDs.

“The management system populates the forwarding data base, alerting certain nodes that, when they see this broadcast identifier, to send [that traffic] out to multiple ports using a group MAC address, a broadcast address,” Hawkins said.

The new E-Tree capability shifts the way PBT and PBB functions are divided in Nortel’s gear.

“The lines get fuzzy now between what’s PBT and what’s PBB,” Hawkins said. “Most multicast applications right now aren’t platinum-level services. They tend to be [closer to] best effort. If that’s the case, you don’t need PBT. It can be done on the PBB side of the switch, with extra MAC headers to keep the customers separated. On the PBT side of the fence, you have tunnels and broadcast tunnels. It takes some knowledge of what you’re doing that may or may not be necessary.”

Nortel’s announcement comes a month after Hammerhead Systems announced a new version of its edge aggregation switch due early next year that would bring both E-Tree and ELAN (or multipoint to multipoint) capabilities to PBT.