Comms chips

Vitesse's Balancing Act

LAS VEGAS -- At the Networld+Interop trade show on Tuesday, Vitesse Semiconductor Corp. (Nasdaq: VTSS) is expected to introduce a highly integrated switch fabric for packet-based metropolitan and access networks.

Called GigaStream, it can support a system with 32 OC48 (2.5 Gbit/s) ports or 64 gigabit Ethernet ports using a total of 24 chips. That puts it at the cutting edge of switch fabric technology, says Rob Sturgill, Vitesse's director of marketing for intelligent switch fabric products.

"It's a true two-chip solution," he claims. The chipset consists of a queuing engine on the line card and a synchronous crossbar switch on the switch card. All queuing, scheduling, and clock functions are integrated on these chips, including the RAM. The chips also contain integrated high-speed serial interfaces (SerDes), so that they can communicate via a high-speed serial backplane.

"High-speed serial links are the best way to get data on and off the chip," says Sturgill. "If you don't integrate the serial technology within the switch fabric then the pin-counts for the switch fabric explode."

But high-level integration is not the only talking point. Vitesse says the really unique feature of its fabric is load balancing, which makes it possible to use the switch fabric in a highly efficient manner.

Simply put, this means that instead of having primary and backup switch cards, the payload is shared across all the switch chips in the system (eight in a fully populated switch). Should one chip fail, the remainder take up the strain.

If it works as advertised, it would be a big deal. A load-balanced switching fabric should improve reliability and latency -- the average length of time it takes a packet to travel from the input port to the output port.

Sturgill claims Vitesse is the first communications chip maker to provide this capability without requiring systems manufacturers to build custom chipsets.

This development highlights the growing importance of off-the-shelf silicon. These days, many systems manufacturers prefer to partner with a reliable external supplier, rather than develop their own silicon in-house. It saves money on development costs and helps them get to market faster.

"We see the emergence of standard-product switch fabrics and backplane transceivers as a major trend in high-speed networking equipment," confirms Allen Leibovitch, director of semiconductor research at RHK Inc.

Other companies working on switch fabrics that could compete with Vitesse include IBM Corp. (NYSE: IBM), PowerX Networks Inc., and Applied Micro Circuits Corp. (AMCC) (Nasdaq: AMCC) through its acquisition of MMC Inc.

GigaStream marks the second announcement in Vitesse's switch fabric roadmap. Over the next 18 months to two years, the chip maker plans to unveil fabrics that scale up to payloads of 640 Gbit/s and native port speeds of 10 and 40 Gbit/s (see Vitesse Extends Product Line).

— Pauline Rigby, Senior Editor, Light Reading http://www.lightreading.com

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