Verizon Communications Inc. (NYSE: VZ) will be using the new Alcatel-Lucent (NYSE: ALU) core router, but not in the core. What the carrier really wants is a lot more Multiprotocol Label Switching (MPLS) in its metro network.

The plan also includes 100Gbit/s Ethernet connections housed on the new Alcalu 7950 XRS line of routers, which were introduced last Tuesday. (See Alcatel-Lucent, Juniper Get Core-Router Upgrades.)

AlcaLu touted the XRS as a core router, but Verizon is more interested in its potential in the metro network. Specifically, the XRSs will be used to aggregate Ethernet traffic before sending it to an MPLS-based core.

"This is all about metro aggregation and the expansion and scaling of the Ethernet edge," says Ihab Tarazi, Verizon's vice president of global network planning.

Wireless backhaul, video, consumer services and cloud usage are all contributing to increased metro Ethernet traffic, so Verizon needs higher-density boxes for moving all that traffic. It also needs to distinguish between services, and that's where MPLS becomes important.

AlcaLu 7450s are doing that job now, but Verizon is going to need the density of the XRS, which AlcaLu says can handle 16Tbit/s of traffic per rack (8Tbit/s if ingress and egress traffic aren't both counted at once).

The change is being driven by increases in bandwidth, but also by more hectic intra-metro traffic. For example, as Verizon caches more video traffic near the network edge, that means it needs to haul more Ethernet around the metro. Wireless backhaul is a contributor as well, Tarazi says.

At its root, the planned metro core isn't so radical, he adds. Really, it reflects the fact that this many services have made the transition to packet networks from time-division multiplexed (TDM) ones. "With all these things going to MPLS, you're going to have to scale the access side. That's the concept here," Tarazi says. "All these things were happening before, but they were happening on T1s, DS3s and Sonet."

The use of MPLS does mean Verizon will be turning away from Provider Backbone Bridging (PBB), its previous choice for the metro Ethernet backbone. MPLS is more reliable and efficient and affords faster turn-up of services, Tarazi says.

PBB isn't departing the Verizon network completely, just in that metro-core capacity. "Some customers still like it on the edge, because they get MAC address scaling," Tarazi says. Verizon expects to introduce 100Gbit/s connections in the metro on the XRS routers and on its optical platforms, Tarazi says. But that's only going to be in spots where the traffic demands it; they won't get crazy with it, and big volumes probably won't start until 2013. Few 40Gbit/s connections will make it into the metro, he adds.

— Craig Matsumoto, Managing Editor, Light Reading