BUFFER DOES A
TRADE SHOW?

FASTER DSL
DATA RATES

CURRENT DSL
TECHNOLOGIES

ADSL: ADSL is a promising technology designed to provide multi-megabit rate channels for services like video. Its deployment is hampered by the fact that there are two competing technologies in place to provide the access CAP and DMT. Even though the bearer channels are simplex (one direction), the data rates are impressive. With downstream rates of up to 6.144Mbits., ADSL can be run over standard. phone lines with POTS at the same time. You can even transport ATM over ADSL--that is, IF you happen to be running ATM at home.

HDSL: If you are lucky enough to have T1 service, HDSL is probably the kind of DSL being used. B8-ZS line encoded with ESF at 1.544 Mb., heck it's only $2000 a month.

SDSL: Think of SDSL as 1/2 of an HDSL. HDSL is a 4-wire service with 2 transmit and receive pairs. If you took exactly one of those pair you could get 768K full duplex. Clever, eh?

IDSL: In all likelihood this is the DSL Pipe technology that will be easily available first. That's because it uses existing ISDN physical layer access. It provides ISDN speeds of 128K, without the overhead of having to bond the B-channels or voice. Most importantly, it provides a migration path to future DSL technologies as they become available.

CABLE MODEMS (They Aren't DSL's): These are fast Mega Bit rate devices that are turning lots of heads. While there are deployment problems, due to the lack of infrastructure to support them, these could really catch on. They don't support voice yet, but both Buffer and I believe with the future development of voice services over The Internet, they could. That should send a chill through the spines of the operating companies and long distance providers. Proposals for deployment of DSL technology is a direct response to the bandwidth available through cable modems.

Buffer wonders why, with so much at stake, implementors and service providers squabble over physical layer details like CAP and DMT for ADSL.

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