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Cisco's 40G switch runs 40nm ASICs, supports OpenFlow

Posted: 06 Feb 2013 ?? ?Print Version ?Bookmark and Share

Keywords:ASICs? OpenFlow? Ethernet? Nexus 6000?

Cisco Systems has recently announced the first 40 Gbit/second Fibre Channel over Ethernet Switch, a 96 port system packing two novel 40nm ASICs. It also describes plans for its first controller for software-defined networking, supporting both OpenFlow standards and the company's proprietary interface.

The new products show Cisco continues to invest in silicon and proprietary software to gain an edge over competitors, even as it embraces standard interfaces such as OpenFlow that aim to level the playing field.

Cisco's Nexus 6000 will pack up to 384 10G or 96 40G Ethernet ports with a port-to-port latency of one microsecond. The company claims it has three times as many ports and a fraction of the latency of switches from Arista Networks, Juniper and others in high-end data center and service provider markets.

At the heart of the switch are two ASICs that form a three-stage Clos network. In an effort to lower the latency of the existing Nexus 5000, engineers took the radical approach of throwing out the scheduler block in the fabric ASIC.

"A packet goes across the fabric and sometimes collides with another packet and you sort out the collisionits going back to [the roots of] Ethernet," said Peter Newman, a principal engineer who worked on the chips. "The trick to making this work is making sure there's enough bandwidth in the fabric so there aren't too many collisions," he said.

Cisco packed into the fabric chip 192 input and 384 output serdes each running at 14 Gbit/s. They are linked on a crossbar switch with an arbiter but no buffer or storage.

"It's not a lot of logic, just I/O," said Newman.

The port chip is more complex, making up the first and last stages of the Clos network. It supports cut-through forwarding, can queue up to 320 Gbits of egress traffic, includes forwarding tables supporting layer-3 look ups and a large memory switch.

The switch is in some ways ahead of the market. Server chips supporting 40G Ethernet are just starting to ship, and none have yet arrived for the Fibre Channel over Ethernet variant that handles both networking and storage. Cisco's server group has such a chip, but it is currently configured for 10G networks.

Cisco goes with the OpenFlow
Cisco's software controller marks its first major step into the emerging market for software-defined networks (SDNs). It embraces both the OpenFlow protocol supporting by the Open Networking Foundationand its own proprietary variant called OnePK.

Proponents of OpenFlow aim to level the playing field for communications systems based on proprietary ASICs, software environments and a jungle of protocols. In their place, OpenFlow aims to create a more open and high-level software environment where network operators and vendors will create and control network features as software applications.

The Cisco controller supports Rest and Java interfaces for programmers writing network applications. The controller then speaks to switches and routers through the OpenFlow or OnePK interfaces.

Cisco says it will support all SDN interfaces including several still in the works, but clearly favors its own OnePK.

"We want to meet developers where they arethis is not a controller tied to any particular technology," said Shashi Kiran, senior director of data center and cloud networking at Cisco. "OnePK can take advantage of our hardware features [but] OpenFlow needs to work against a more abstract switch model," he said.

The controller is still in beta testing. Cisco expects it could support Version 1.3 of OpenFlow when the controller is released in the middle of the year.

- Rick Merritt
??EE Times

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