On Tue, Jan 19, 2016 at 12:36 PM, <gso...@yahoo.co.uk> wrote: > (i) a. With both Linux or Windows all downloads tend to hover around 100 KB/s > on a 50 Mb/s cable Internet connection > b. if I run a processor intensive program while downloading (typically at the > moment a video of a burning fireplace) then the download rate starts to > return to normal > c. if I am using some sort of encryption (SSH forwarding, OpenVPN) then there > will be a short burst of speed close to the full bandwidth at the start of > the download before falling back to circa. 100 KB/s > > ii) However whenever I have in the past booted up and configured an OpenBSD > install then the full 50MiB/s download speed is available without any issues. > Can anyone make any sense of the above - why should there be no problems with > OpenBSD? > > This all happens on an old Compaq Presario C500EA - > http://support.hp.com/us-en/product/Compaq-Presario-C500-Notebook-PC-series/3318986/model/3357395/document/c00843649/ > > I appreciate this is not an OpenBSD issue, but I figured if there was anyone > who could figure this one out this would probably be the place to ask. >
Maybe your switch or cable router have rather shallow buffers, and are not able to absorb the amount of data that your NIC is sending without backpressure, which leads to a see-saw in performance. Some drivers will send way more data to the NIC in a burst than they should. This is a total shot in the dark, but try disabling TCP segmentation offload in Linux, e.g. ethtool -K eth0 tx off sg off tso off I'd also look at your network stack and ethernet driver stats to see if there are any errors accumulating, e.g. retries, bad MTU, etc.
