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Comms chips

PMC, TranSwitch Get Edgy

ATLANTA -- Supercomm 2003 -- Continuing to preach the gospel of virtual concatenation, PMC-Sierra Inc. (Nasdaq: PMCS) and TranSwitch Corp. (Nasdaq: TXCC) are at Supercomm this week touting chips that seek to fill a gap in the technology's resumé.

Virtual concatenation makes Ethernet-over-Sonet more efficient by allowing multiple Ethernet streams to share a particular Sonet pipe (see Making Sonet Ethernet-Friendly). Both companies already have devices that combine two Gigabit Ethernet streams into an OC48, and TranSwitch even has a chip for packing traffic into an OC3. The new chips extend the concept to include 10- or 100-Mbit/s Ethernet and an OC12.

The new speeds are a good fit for access and metro networks, writes Simon Stanley, principal analyst with Earlswood Marketing Ltd., in an email exchange with Light Reading. "Much of the Sonet/SDH infrastructure is OC12, and eight 10/100 lines are a good match."

It's yet another step forward into telecom networks for Ethernet. As it gets more economical to put Ethernet directly over Sonet, Ethernet services "could effectively be replacing the T1 access we have today," says Jon Ames, director of strategic marketing for PMC's service provider division.

PMC introduced two devices this week: the PM5333 Arrow 8xFE, which packs eight lines of 10- or 100-Mbit/s Ethernet into an OC12; and the PM5329 Arrow 24xFE, which combines 24 lines into an OC48 (see PMC-Sierra Debuts a Bunch of Gear).

TranSwitch's new chip is the EtherMap-12, combining eight 10/100-Ethernet lines into an OC12. TranSwitch also introduced the PHAS-12N framer to hook up with the new EtherMap part (see TranSwitch to Demo Ether/Sonet Solution).

At first glance, the combined announcements seem like trouble for TranSwitch, as it's got one of its bigger competitors muscling into its lower-end turf. That's particularly worrisome, considering the recession hasn't been particularly kind to TranSwitch, whose revenues have lurked below $5 million for eight quarters in a row. In an April report detailing TranSwitch's first-quarter earnings, analyst Jeremy Bunting of Thomas Weisel Partners noted that the company's been drumming up design wins, but that revenues could be "choppy" until the money from those wins kicks in.

Earlswood's Stanley says EtherMap is a promising product that could help boost business. "If they can fully exploit these market-leading products they can pull in significant business for their less interesting TDM, Sonet, and ATM devices such as the PHAST-12N," he writes.

Moreover, EtherMap-12 includes a Gigabit Ethernet media access controller (MAC) and a proprietary multiplexing scheme that could prove attractive. It allows traffic from different sources to share a Gigabit Ethernet stream yet be assigned to different virtual concatenation channels.

"So let's say you had traffic that was destined for an Internet service provider, as opposed to traffic destined for your intranet," says Bill Bartholomay, TranSwitch CTO. "You can assign these to different physical ports even though they came in the same Gigabit Ethernet."

"This allows a service provider to provision and manage several connections with individual quality-of-service parameters over a single physical link," Stanley writes. "This is likely to be a key feature in future applications."

One notable point is that the new PMC and TranSwitch chips support low-order virtual concatenation, which involves granularity down to the T1 or E1 level, for Sonet and SDH respectively. Nearly all virtual concatenation chips to date have been high-order devices, operating at the STS1 level. Until now, only a handful of companies -- including TranSwitch and Galazar Networks Inc. -- have supported low-order virtual concatenation.

— Craig Matsumoto, Senior Editor, Light Reading

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