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Despite Vancouver, British Columbia-based PMC-Sierra Inc’s statement that it planned to press ahead with its technology for 25Mbps Asynchronous Transfer Mode after the ATM Forum had rejected it as a standard (CI No 2,611), little has been heard from the firm since, and it appears that – at least as regards the local area network – the technology is dead. The Forum picked a rival proposal from the Desktop ATM25 Alliance, led by IBM Corp, over Sierra’s proposal, which is based on a fractional Synchronous Optical Network-based specification. Vernon Little, Sierra’s Manager of LAN Products, said the company has since decided that there really is very little role for 25Mbps Asynchronous Mode within the local area network – either using Sierra’s technology or the ATM Forum’s standard – for two reasons. Firstly, the price point of faster Asynchronous Mode switches is now so low that moving to a lower speed is is more or less redundant. He cited the company’s 155Mbps single chip adaptor as an example of this price erosion: the chip for the LASAR-155 will ship at $125 in volume quantities, enabling 155Mbps network interface boards to be marketed for as little as $300. Little’s second reason is that 25Mbps Asynchronous Mode will compete directly with switched Ethernet and network managers are more likely to go with the latter technology since it is perceived as being more tried and tested. That said, the technology is finding something of a home in other markets: Little said the Digital Audio Video Council is using a related technology for residential broadband applications. This does not use the Synchronous Optical Network frame per se, said Little; it is based on an asymmetrical design – with different rates for the upstream and downstream paths, and uses forward error correction which was not incorporated into Sierra’s original proposed standard. It does, however, use the same bit rates as in Sierra’s original proposal, enabling Sierra to capitalise on at least some of the work it put into the specification.

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CBR Staff Writer

CBR Online legacy content.