Volume 9, May 22, 2000

"Getting up to Speed"
by Bob Oas, assistant editor of Inside Technology Training, Inside Technology Training, April 2000, p. 47

"With all the broadband technologies out there, choosing the right one for your organization can be daunting. While one technology might be ideal for certain users, it simply may not be feasible for others." (p. 47) "The first question to ask is, What are you trying to accomplish?" (p. 47) High-bandwidth technologies include:

• The Big Ts – "A T1 line is a permanent, two-way connection that provides high-speed access at rates of up to 1.544 mbps." (p. 47) "A T3 line is even fatter, providing Internet connectivity at 45 mbps, which is why it’s the technology of choice for many Internet service providers (ISPs)." (p. 47)
• ISDN – "ISDN is actually comprised of three channels: a 16 kbps signaling data channel and two 64 kbps bearer channels. The data channel transmits dialing and ringing information, while the bearer channels handle voice and data signals." (p. 47) "Unlike the T1 and T3 lines, the rate at which information is pushed upstream (back to the company) is only slightly higher than that of a 56K dial-up modem." (p. 47)
• DSL – "There are essentially two types of DSL: asymmetric DSL (ADSL) and symmetric DSL (SDSL). ADSL is asymmetric in that its bandwidth is not equal to and from a learner’s computer. In some cases, ADSL can flow 8 mbps downstream and 1.5 mbps upstream – but 1.5 mbps and 384 kbps, respectively, is more likely. SDSL offers equally broad bandwidth both ways." (p. 47)
• Cable Modems – "The same wire feeding cable TV into your living room is capable of providing Internet access at 10 mbps." (p. 48) "Unlike DSL, cable modem access is not available in symmetric form, so upstream connectivity is typically limited to the 200 kbps to 2 mbps range. And because cable modem access is configured on a network neighborhood, the rate at which you connect depends on the number of other cable modem users in your area." (p. 48)
• Satellite – "Connecting to the Internet via satellite is similar to getting your TV signals from one. Data transmissions are beamed down from a satellite orbiting 22,200 miles above Earth, then translated and decoded upon entering a 21-inch dish." (p. 48) "Satellite transmissions are one-way. So although information is received at 400 kbps, a separate ISP connection (typically a dial-up modem) is required to send data upstream." (p.50)

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