Allayer chip switches Ethernet traffic onto Sonet nets

The ALPOS48 is the first off-the-shelf part to handle the translation between Ethernet packets and Sonet frames, Allayer officials said. The part is being marketed as a key component to link traffic between the LAN and the WAN.

"Companies have been doing this but have been using ASICs," said Mohan Maheswaran, vice president of marketing for Allayer. "Many other [systems providers] now can play in that game."

To transmit Ethernet packets over Sonet, the ALPOS48 requires an additional framer and physical-layer Sonet component, such as those offered by Applied Micro Circuits Corp. or Vitesse Semiconductor Corp.

Interest in marrying Ethernet with Sonet has increased as speeds on both sides have converged. Ethernet has traditionally stayed inside enterprise networks and Sonet inside the WAN, but the two are beginning to mingle as their speeds begin to match, Maheswaran said.

Single stream

Specifically, Gigabit Ethernet with 8-bit/10-bit encoding comes out to 1.25 Gbit/s. Allayer's AL1022 Ethernet switch happens to carry two ports of Gigabit Ethernet that can be melded into a single 2.5-Gbit/s stream. Hence, Allayer is touting the ALPOS48 and AL1022 as a two-chip packet-over-Sonet interface, with a RoX-II bus connecting the two.

Even more promising is the 10-Gbit/s Ethernet standard now in the works, which will nearly match the speed of OC-192 transmission and allow Ethernet and Sonet to interact in the WAN. Allayer does have a chip in the works to translate between 10-Gbit Ethernet and OC-192, and an announcement of that chip should come within a few months, Maheswaran said.

While other companies are likely to develop Ethernet-Sonet interface chips, Maheswaran claimed Allayer is one of the few with expertise on both sides of the technology. "You really have to understand Ethernet switching, and in addition, you have to understand things like MPLS, Layer 3 and above functions, and decide how to configure streams going out onto OC-48," he said.

The APLOS48 is sampling now and is due to ship in July, priced at $300 in quantities of 1,000.