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Disadvantages of 56K
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56K for downloads only
A 56K connection is asymmetric: it's faster for downloading than for uploading. Downloading means receiving data from another computer (for example, viewing a Web page or receiving email). Uploading means sending data to another computer (for example, sending email or uploading files to your Web page.) The download speed can be as much as 56K, but the upload speed will initially be only 28.8K or 33.6K. Lucent has stated that upload speeds for K56flex may exceed 40K in the future, though this has not been publicly demonstrated. Many other high-speed technologies (e.g. ADSL and cable modems) also have asymmetric rates. V.34 modems (28.8K and 33.6K) support asymmetric connections to compensate for poor line quality in one direction, but the upload and download rates are usually very close to one another. (See the 28800 FAQ below for a discussion of split speeds in V.34 modems.) The lower upload speed isn't significant for most users. Most Internet surfers spend far more time downloading than uploading, and most of their uploading is, as Rockwell puts it, "key strokes and mouse clicks." The upload limitation does limit the utility of 56K for certain uses. In particular, it makes 56K impractical for low-end server use, or for videoconferencing. For those applications, ISDN is superior. (See "56K's High Speed Competition" for more information about ISDN and other high speed technologies.) Why the limit? When downloading over a 56K connection, data is changing from a digital signal to an analog signal. Digital-to-analog conversions are perfectly accurate, so downloading at speeds up to 56K is possible. When uploading, data is changing from an analog signal to a digital signal. Analog-to-digital conversions are imperfect, so noise is introduced into the signal.
Links Lucent Technologies K56flex FAQ Navas 28800 Modem FAQ |
