Editing Dial-up Internet access (section)

===Using compression to exceed 56k===
The [[ITU-T V.42|V.42, V.42bis]] and [[ITU-T V.44|V.44 standards]] allow modems to accept compressed data at a rate faster than the line rate. These algorithms use [[data compression]] to achieve higher throughput.

For instance, a 53.3&nbsp;kbit/s connection with V.44 can transmit up to 53.3 × 6 = 320&nbsp;kbit/s if the offered data stream can be compressed that much. However, the compression ratio varies considerably. ZIP archives, [[JPEG]] images, [[MP3]], video, etc. are already compressed.<ref>{{cite web |url=https://www.pricenfees.com/digit-life-archives/modem-compression-v-44-v-42bis |title=Modem compression: V.44 against V.42bis |access-date=2008-02-18 |author=Pavel Mitronov |publisher=Pricenfees.com |archive-url=https://web.archive.org/web/20170202062749/https://www.pricenfees.com/digit-life-archives/modem-compression-v-44-v-42bis |archive-date=2017-02-02 |url-status=dead }}</ref> A modem might be sending compressed files at approximately 50&nbsp;kbit/s, uncompressed files at 160&nbsp;kbit/s, and pure text at 320&nbsp;kbit/s, or any rate in this range.<ref>{{cite web |url=http://fndcg0.fnal.gov/Net/modm8-94.txt |access-date=2008-02-18 |title=What You Need to Know about Modems |author=Karl Willdig |work=Fermilab Data Communications and Networking Group |publisher=Fermi National Accelerator Laboratory |url-status=dead |archive-url=https://web.archive.org/web/20070104124418/http://fndcg0.fnal.gov/Net/modm8-94.txt |archive-date=2007-01-04 }}</ref>

====Compression by the ISP====
{{Main|Web accelerator}}
As telephone-based Internet lost popularity by the mid-2000s, some Internet service providers such as TurboUSA, [[Netscape]], CdotFree, and [[NetZero]] started using data compression to increase the perceived speed. As an example, EarthLink advertises "surf the Web up to 7x faster" using a compression program on images, text/html, and SWF flash animations prior to transmission across the phone line.<ref>{{Cite web|url=http://www.earthlink.net/dialup/|title=EarthLink Dial-Up Internet service – fast, reliable dialup access nationwide.|website=www.earthlink.net|access-date=2017-01-12}}</ref>

The pre-compression operates much more efficiently than the on-the-fly compression of V.44 modems. Typically, website text is compacted to 5%, thus increasing effective throughput to approximately 1000&nbsp;kbit/s, and JPEG/GIF/PNG images are lossy-compressed to 15–20%, increasing effective throughput up to 300&nbsp;kbit/s.

The drawback of this approach is a loss in quality, where the graphics acquire [[compression artifacts]] taking on a blurry or colorless appearance. However, the transfer speed is dramatically improved. If desired, the user may choose to view uncompressed images instead, but at a much slower load rate. Since streaming music and video are already compressed at the source, they are typically passed by the ISP unaltered.