Yes, it's time for another round of big numbers for core routers.

Juniper Networks Inc. (NYSE: JNPR) came out today saying it's upgrading its T series to 250 Gbit/s per slot.

That appears to be a pre-emptive strike against Cisco Systems Inc. (Nasdaq: CSCO), which is said to be readying an announcement involving per-slot capacity of 120 Gbit/s. Cisco's plan could involve an upgrade to the CRS-1, rather than a wholly new box. (See Rumor: Cisco Prepping CRS-1 Successor.)

Juniper's numbers, at least on paper, would also outdo the 100 Gbit/s per slot touted so far by Alcatel-Lucent (NYSE: ALU) and Huawei Technologies Co. Ltd. In theory, Juniper says, it will be able to get 4 Tbit/s through a half-rack box.

Technically, all Juniper is announcing for now is a new switch fabric that will expand the system's switching capacity. Trial systems with the fabric should arrive later this year, with real sales to start in 2011.

The other piece, to come later, would be the interface cards that take advantage of the newly opened bandwidth. These will include cards sporting 10-, 40-, and 100-Gbit/s ports, says Alan Sardella, Juniper's senior product marketing manager.

The upgrade continues Juniper's trend of using its own chips for its franchise router lines. The company announced in October that it's similarly upgrading its edge routers, under the flashy name MX 3D, with a chipset called Trio. Those chips will be the foundation for another Juniper in-house project: a mobile packet core, to counter Cisco's acquisition of Starent. (See Juniper Takes Over the Network, Juniper Looks Inward for Wireless, Juniper's Wireless Worry, and Cisco/Starent Deal Hurts Juniper.)

When might Juniper start considering merchant processors or switch fabrics for its franchise routers?

"There's a New Yorker cartoon -- I don't know if you've ever seen it -- where this guy's going through his datebook and says, 'How about Never? Does Never work for you?' " Sardella says. Juniper's concern is that an outside chip isn't going to strike exactly the combination of intelligence, table sizes, power, and space that Juniper would need. "To be commercially viable at this stage, you've got to do it yourself," he notes.

Sardella claims the T series has the headroom for yet another capacity upgrade, but Juniper isn't giving out details about that.

— Craig Matsumoto, West Coast Editor, Light Reading