3/16/2010 -- Cisco Systems Inc. announced an update last week for its massive Carrier Routing System-1 (CRS-1), almost six years after that product first shipped.

Officials say the forthcoming CRS-3 will deliver three times the capacity of its flagship predecessor, which Cisco once billed as the largest and most scalable routing system ever developed. The CRS-1, for the record, can expand to support up to 92 Tbps of incoming and outgoing traffic in a 72-way multi-chassis configuration. When it ships, the new CRS-3 will support more than 320 Tbps (incoming and outgoing) in a similar 72-way multi-chassis setup, officials said.

CRS-3 isn't expected to ship until early next year. And Cisco's rivals aren't sitting still: arch-enemy Juniper Networks Inc., for example, last month announced an upgrade for its T1600 routing behemoth. If Juniper hews to its (perhaps overly) optimistic timetable, it could be able to match Cisco's per-chassis capacity by the time CRS-3 finally ships.

The upshot, experts say, is that the core routing space will be more combative than it was when CRS-1 debuted six years ago. Not that the competition between Cisco, Juniper, and other players wasn't fractious then, too.

This time around, there are a few eerie similarities. For example, even though CRS-1 laid claim to next-generation routing bragging rights, it was in some respects built on last-generation technology: it offered the same 40 Gbps-per-slot capacity that Juniper introduced with its T640 router in 2002. More recently, Juniper (again) beat Cisco to the per-slot punch, shipping 100 Gbps line cards in its flagship T1600, which supplanted CRS-1 for single-chassis bragging rights in 2007.

The CRS-3 announcement means that Cisco is again poised to reclaim the core routing crown. Not that capacity bragging rights, for either single- or multi-chassis routers, matter to Cisco executives.

"The next generation Internet is upon us and we are confident that the Cisco CRS-3 will play a crucial role as service providers like AT&T deliver an exciting, new array of video, mobile, data center and cloud services," said Pankaj Patel, vice-president and general manager of Cisco's Service Provider Group, in a statement. "The Cisco CRS-3 is well-positioned to carry on the tradition of the Cisco CRS-1, become the flagship router of the future and serves as the foundation for the world's most intelligent and advanced broadband networks."

Juniper was quick to push back against Cisco's CRS-3 marketing blitz, claiming that it expects to match CRS-3's single-chassis capacity once it starts offering 250 Gbps line cards for the T1600 later this year.

Juniper first announced its 250 Gbps-per-slot refresh last month after rumors started swirling about Cisco's upcoming CRS-3 announcement

And while Cisco's multi-chassis strategy lets it scale CRS-1 (and CRS-3) beyond what Juniper can today achieve with its T1600 -- that product supports a maximum of 25 Tbps of traffic via 16 linked chassis -- experts question whether anyone really needs (or has enough spare data center space to house) double or triple-digit terabit scalability. None of Cisco's reference customers approach CRS-1's 92 Tbps limit. The biggest CRS-1 adopter is Verizon Wireless, which uses CRS-1 to support what most experts believe is less than 10 Tbps of traffic.

Big, yes. Huge, even. But far short of 92 Tbps.

There's even a sense in which Cisco's multi-chassis proposition stretches credulity, Yankee Group analyst Jennifer Pigg argues on her blog.

"No one is going to string together 72 … chassis, each [of which are] three feet deep and over six feet high [as well as two feet wide], to achieve the parlor trick of the 322 Terabit router," writes Pigg. "I'm not saying that we'll never need a 322 Tbps core router.  I'm just saying that when we do, it's not going to be delivered by the CRS-3."

Pigg, like other industry watchers, wonders just how effectively existing customers are making use of CRS-1's capacity – especially in scale-out multi-chassis configurations. Cisco, she points out, isn't especially forthcoming on this tip. "Yankee Group believes that the vast majority of CRS-1s … [are] one- to five-chassis systems, and we know of no systems over 10 chassis," Pigg continues. What's more, some CRS-1 customers are just starting to explore their multi-chassis options. "By the time [CRS-1] customers [started moving] into the double digits of chassis … Cisco introduced the CRS-3, which could deliver three times the speed per chassis," she explains.

All the same, Pigg is skeptical about Juniper's ability to deliver 250 Gbps line cards before Cisco officially ships CRS-3 early next year: "[W]e expect Cisco to be able to claim fastest per chassis system for up to 12 months, after which Juniper will reclaim that title until Cisco ships a 250Gpbs slot."  --By Stephen Swoyer