# Uploading large files affects dl speed? **URL:** \ **Category:** Factual Questions\ **Created:** [January 16, 2006, 9:57pm UTC](https://boards.straightdope.com/t/uploading-large-files-affects-dl-speed/340268 "2006-01-16T21:57:25Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [January 16, 2006, 9:57pm UTC](https://boards.straightdope.com/t/uploading-large-files-affects-dl-speed/340268/1 "2006-01-16T21:57:25Z")
Hi folks, It’s easy to tell when LadyDvl is uploading a large (700 + Mb) file to one of our client’s servers—the rest of the net slows to a crawl. I’ve always thought it a bit odd that her uploads take so long but never really looked into it, figuring that our cable ISP provides just a wee bit of bandwidth in that direction. But then it just struck me how odd it is that uploading has such a dramatic affect on download speed, given that our available download bandwidth is so much larger than our upload’s. If this is the case, can anyone here shed some light on why? If it shouldn’t effect download speed, where do we begin diagnosing the problem? I’m on an XP box, she’s on a Mac OSX box, both of us go through a D-Link router on RR cable Internet. Thanks, Rhythmdvl ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [January 16, 2006, 10:20pm UTC](https://boards.straightdope.com/t/uploading-large-files-affects-dl-speed/340268/2 "2006-01-16T22:20:47Z")
This is a fact of life with cable broadband. Uploading files at near the max. upload speed just kills the connection. The system was designed for fast downloads, the thinking was that only minimal uploading was needed, e.g., for requesting web pages and sending email. If your upload software allows it, throttle the upload speed to something like 1/2 to 3/4 of the max upload speed. ---
**Author:** ![KeithT](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@KeithT](https://boards.straightdope.com/u/KeithT)\ **Post date:** [January 16, 2006, 10:59pm UTC](https://boards.straightdope.com/t/uploading-large-files-affects-dl-speed/340268/3 "2006-01-16T22:59:16Z")
The only solution is capping the upload rate – it’s not a problem on your end, simply the way network communications work. Underneath HTTP, FTP, and most the other “high level” network protocols lies [TCP](http://en.wikipedia.org/wiki/Transmission_Control_Protocol). This is a robust transport protocol that ensures that data is transmitted without any losses. However, this requires the receiving computer to send back an acknowledgement after each small packet of data is sent. If you’re uploading a large file, the acknowledgment packets can’t be sent quickly – they have to wait for space between the outgoing packets of the large file. Since any other computer that’s trying to send you data, whether it’s email or web pages, has to wait for these acknowledgements, everything slows down. For time-critical applications where a few lost bits don’t matter, such as streaming video, games, or VoIP telephony, a different protocol ([UDP](http://en.wikipedia.org/wiki/User_Datagram_Protocol)) is used. Because UDP just sends packets without waiting for acknowledgments, it’s fast, but runs the risk of dropping out. ---
**Author:** ![Exploding\_Kitchen](https://avatars.discourse-cdn.com/v4/letter/e/c89c15/32.png) [@Exploding\_Kitchen](https://boards.straightdope.com/u/Exploding_Kitchen)\ **Post date:** [January 17, 2006, 12:13am UTC](https://boards.straightdope.com/t/uploading-large-files-affects-dl-speed/340268/4 "2006-01-17T00:13:02Z")
You also have the issue that cable and ADSL, unlike SDSL and T1+ dedicated connections, can’t send and receive information at the same time. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [January 17, 2006, 1:39am UTC](https://boards.straightdope.com/t/uploading-large-files-affects-dl-speed/340268/5 "2006-01-17T01:39:43Z")
> [@Exploding Kitchen](#): > > You also have the issue that cable and ADSL, unlike SDSL and T1+ dedicated connections, can’t send and receive information at the same time. Cite? From [here](http://www.dansdata.com/bandwidth.htm) > [@](#): > > A humble modem link is, at least, full duplex. You can be downloading at 44 to 52 kilobits per second, and uploading at 33.6 kilobits per second, simultaneously. **All of the popular broadband technologies are full duplex, as well.**