Copper Mountain gear tuned for IDSL

Palo Alto, Calif. - Copper Mountain's new network box squeezes every last bit of bandwidth out of high-speed ISDN digital subscriber lines (IDSL) for use as dedicated remote access links to corporate networks.

The company last week rolled out the CopperRocket 201 Multi-Speed IDSL access device. CopperRocket can carry data at 144K bit/sec over regular phone lines, boosting the speed of the connection by 12.5% over conventional ISDN hardware.

Traditional ISDN terminal adapters at customer sites can support either a 64K bit/sec or 128K bit/sec data stream using one or two 64K bit/sec ISDN B channels. Copper Rocket 201 adds an extra 16K bit/sec to the line by mixing in D channel capacity, which is reserved for signaling in regular ISDN service.

The device represents a trade-off between price and performance, according to Raymond Keneipp, an analyst with Current Analysis in Sterling, Va. Many conventional ISDN routers cost about $200 less than the $595 Copper Mountain is charging for CopperRocket 201, but they cannot support 144K bit/sec speeds.

For customers switching from ISDN to IDSL, it makes sense to use the existing ISDN terminal adapter to support IDSL, says Bill Yundt, vice president of network operations for WebTV in San Francisco, which uses IDSL for remote access. In that case, the cost of the customer equipment is zero, he says.

But for customers that do not already own an ISDN terminal adapter, buying one that supports a full 144K bit/sec might make sense, Keneipp says.

CopperRocket 201 also supports a variety of speeds that can be adjusted remotely by service providers. An IDSL service provider could sell a customer a 64K bit/sec IDSL service initially, for example, and then boost the bandwidth to 128K bit/sec or 144K bit/sec if the customer wanted more speed. That increase could be accomplished by downloading software to the customer's CopperRocket 201 from the service provider's switching office, Copper Mountain says.

Changing the speed remotely requires the service provider to have Copper Mountain IDSL modems in its switching office fitted with new 24-port IDSL line cards. Copper Mountain announced last week that those line cards are also available at a suggested retail price of $7,995.

Yundt said IDSL was a good answer for WebTV for two reasons. IDSL from Covad costs less than ISDN from Pacific Bell if the remote user is logged on for more than 10 hours per week. ISDN is billed based on use and IDSL is billed on a flat fee. And second, the end users liked it better.

Because WebTV's IDSL service is a dedicated connection, end users do not have to dial in, pass through security and wait for a connection each time they want to tap corporate resources. That gives them the perception that IDSL is faster than ISDN, according to a survey of WebTV's IDSL users.

IDSL is deployable as far as 36,000 feet from a service provider switching office, triple the distance of some other DSL variants. That raises the probability of reaching more remote users with IDSL than other, faster DSLs.

Pure DSL technologies require high-quality phone lines that have been conditioned by removing devices that would interfere with DSL transmissions. They are also limited by distance. The longer the line, the slower the speed of the DSL connection.

IDSL, with its roots in ISDN, can be delivered at top speed over an 18,000-foot phone line, and that distance can be doubled with a repeater.

IDSL can also be supported over carrier equipment known as digital loop carriers (DLC). Other forms of DSL require a special line card in the DLC, but IDSL can pass through standard DLC gear to the carrier switching office. DLCs serve about 20% of phone lines in the U.S.

Details of Copper Mountain's IDSL offering