ADSL Conundrum

October 1997 / BYTE Hardware Lab Report / ADSL Conundrum

Because the technologies that are used by ADSL modems are too different and are not interchangeable -- and they have no formal standardized test suites -- we declined to choose a Best Overall ADSL winner from among them. However, we did uncover some interesting data during our testing.
The distance between the modem and the central office plays a significant role in an xDSL modem throughput. The closer the m odem is to the central office, less signal degradation occurs.
The good news is that manufacturers are being realistic about their claims of ultimate throughput. In we ll-tailored packet-blast tests over clean lines, we were able to prod each ADSL modem to almost its advertised maximum throughput speed.
Packet blasting produces high numbers, but it's hardly a realistic operating mode. We wanted a sense of how these modems would perform with real applications.
To imitate a typical application, a single client opened eight concurrent IP sessions over a clean line with a mixture of FTP and HTTP -- simulating a typical Web-page access. The accompanying graph shows that the throughput results we measured compare well to the speed claims of the vendors.

Clean Lines Deliver the Data
illustration_link (12 Kbytes)

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Matthew Wilson
My approach to software engineering is far more pragmatic than it is theoretical--and no language better exemplifies this than C++.

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