A Dial-up Modem Data Transfer Rate Test

November 2003 (Revised July 2008)

This document transmits 500,000 somewhat random and therefore largely uncompressible characters, times the transmission, and calculates the data throughput actually achieved. Although Gzip compresses the test data to 96% of original size, Compress, which uses LZW, does not compress it at all. Modem V.42bis compression uses LZW and so can be presumed to not compress the data. So the result gives the uncompressed data transfer rate. Text will generally achieve twice that with V.42bis or three times with V.44 compression. This test will take nearly two minutes on a fast dialup connection, and can take more than double that on a slow one.


You should expect an end-to-end data transfer rate no less than 28.8 kilobits per second. In Alaska, this is the minimum standard for all state-regulated phone lines. Meeting it requires a connect speed of at least about 35 kilobits per second, per recent tests.

By February 13, 2003, a telephone company shall provide an end-to-end data transfer rate of no less that [sic] 28.8 kilobits per second; [3 AAC 53.705(f)(1)(C)][emphasis added].

If the connect rate is about 48000 but the throughput is only about 30 kbps, you probably get dial tone via conventional loop start copper lines but have old-fashioned 'quad' premises wiring limiting the throughput. Quad cable with four parallel wires, usually red, green, black, and yellow, is notorious for picking up interference, including audible buzz and hum. If you have this, you may be able to improve throughput considerably by using modem commands to limit the connect rate to a lower speed such as 42666 (the USR 5610b uses &n28). I've seen this boost throughput from 30 to 37 kbps. You may be able to throughput dramatically by running a geniune twisted pair cable, such as a radio shack 100 foot extension cord of twisted wire instead of parallel wire, directly from the from the telephone company network interface device to the computer. I have seen this boost throughput from 30 to 44 kbps, which is about the best you get on a dialup connection.

If the connect rate is about 44000 but the throughput is less than 19 kbps (usually 16-18), you probably get dial tone via cable company digital phone service, which uses Voice over Internet Protocol (VoIP) over local cables. If you have this type of service, you may be able to improve throughput dramatically by using modem commands to limit the connect rate to 40000 (the USR 5610b uses &n26). At 42666, throughput is only about 16-18 kbps. Slow it to 41333 and it rises to 31 kbps. Show it to 40000, and it rises to 35 kbps, which is usable. However, there may be serious difficulty getting connecting -- redialing a dozen times can be required. Downloading a firmware update from the modem maker may help with this. But even if connecting is resolved, there is a problem of the line dropping from 5 minutes to 2 hours into a connection. And after such drops, it is not uncommon to have to reboot to establish a new connection. Adding insult to injury, the FCC, under a dubious reading of their interstate commerce authority, exempted this form of phone service from state regulation, making it a take it or leave it proposition. However, the Alaska Regulatory Commission has told me that within the state you have the right to obtain the state-regulated non-VoIP service if you need it. And in my experience, GCI customer service will switch a customer lines from digital to loop start when truly needed for service reasons.

If the connect rate is 28800 or less (commonly about 26400) and the data throughput even lower, you are probably getting dial tone via a primitive subscriber line carrier system that in Alaska is aruably not even a legal service offering. Sometimes phone companies provide a second phone line over the same copper pair as the primary line using subscriber line carrier. Modern varieties of this can meet Alaska's minimum standard, but old equipment of this type commonly yields a connect speed no better than 26.4 kilobits per second, with data throughput being much less than this. Arguably, phone companies have been forbidden from installing such equipment in Alaska since 2003, per the Alaska Administrative Code modernization requirements. If you are having slow service because of a new installation of this sort, you should complain. But because GCI leases lines from ACS it may be difficult to get results. ACS may see no reason not to use an old carrier box unless someone expressly tells them the line is for a modem. But communications between GCI and ACS aren't great. In one instance I resorted to filing an informal complaint with the Regulatory Commission of Alaska with copies to GCI and ACS. It was the only way to get word to ACS that the line was for a modem. Within a few hours, ACS had called, apologized, and removed the carrier box, solving our slow data throughput problem. Isn't competition grand?

If you must complain, sending a letter to your telephone company's corporate contact address may be easier and more effective than calling. For GCI and ACS in Alaska, the addresses are on the company corporate websites (gci.com: Contact GCI; acsalaska.com: AboutACS, contact ACS). Try to clearly explain the issue and request an upgrade for the line you use for data. If you have a voice line but don't need data speed on that, you should say so. If the response is that you are only entitled to dial tone, or a 'voice grade' line, consider filing an informal complaint with the regulator. In Alaska, that's the Regulatory Commission of Alaska (RCA). There is more than one case where the RCA has ordered refunds of telephone bills to entire communities after phone companies provided service not meeting the modernization requirements. The Regulatory Commission of Alaska: informal complaint procedure is a very quick and easy way to file a complaint, but you should not do this until after making every effort to resolve the problem directly with the phone company. If you must file an informal complaint, sending a copy to your phone company's customer service e-mail, and if known, that of the underlying carrier (e.g., support@gci.net; info@acsalaska.net) can have astonishingly fast results. The problem might even be fixed before the RCA staff reads your complaint. But don't count on it.

W. Gregg, A dialup-modem data transfer rate test (2008) (w-gregg.juneau.ak.us/ 2003/ text/ 2003k00-dialup-throughput).