single channel OC192 (10 Gbit/s) packet over Sonet (POS)

single channel OC192 ATM

quad channel OC48 (2.5 Gbit/s) POS

quad channel OC48 ATM

10-gigabit Ethernet LAN PHY -- a souped up version of gigabit Ethernet with ten times the data rate, and various bells and whistles in the form of extra traffic management features

10-gigabit Ethernet WAN PHY -- this version of 10-gig Ethernet has been tweaked in a different way so that it can be sent across existing Sonet links at the slightly lower bit rate of 9.953 Gbit/s

The seventh mode is supported on a separate, single chip, which handles 10 ports of gigabit Ethernet traffic.

PMC-Sierra claims its chips score a number of firsts. It says it's the first vendor to release chips supporting the new high-speed bus. And that's as it should be, since PMC Sierra is the prime mover behind the Saturn development group, the consortium of chip makers and end users that defined the POS PHY Level 4 standard.

More significantly, the company claims to be first to develop chips that support both the LAN and WAN versions of 10-gigabit Ethernet. Competing chip makers agree that this is an important development but one that doesn't surprise them.

"It falls right along the lines of what's been discussed at the 10 Gigabit Ethernet Alliance," says Jeff Downs from the Ethernet group at Vitesse Semiconductor Corp. (Nasdaq: VTSS). "The roadmap for 10-gig Ethernet is pretty much in the open, so this is a target for many chip makers."

Downs concurs that PMC's product announcement is a first as far as he's aware, but believes other vendors won't be far behind. "In the next three to six months you'll see more product announcements of this nature," he adds.

He says that Vitesse will have some 10-gig Ethernet chips of its own soon, through its acquisition of Exbit Technology A/S (see Vitesse Buys Exbit).

Ultimately, it is not clear if support for extensive numbers of protocols on the same chip will be the best way to go, Downs notes. "In a perfect world, these kinds of multiprotocol solutions are a nice way to go," he says. "But when it comes down to the implementation details, the question is, is it the most efficient way to do things? You have to make a tradeoff between cost, chip area, power consumption, and so on. Are vendors willing to pay the premium?"

He also points out that PMC's announcement concentrates on single-channel inputs for 10-gigabit Ethernet and doesn't indicate support for a XAUI ("Zowie") type interface, which brings in a 10-Gbit/s signal on four wavelengths. This would prohibit the use of one of the optical module options laid down in the 10-gig Ethernet standard, which uses four-color coarse wavelength-division multiplexing (CWDM) (see IEEE Nails Down 10-Gig Ethernet Basics).

-- Pauline Rigby, senior editor, Light Reading http://www.lightreading.com