I originally posted this on Reddit, but it might make more sense here.
About a year ago I upgraded from Virgin's 350mbps to the 500mbps band. Prior to this upgrade, speed tests had nearly always shown I was getting the full 350mbps download speed. Following the switch to 500mbps I never actually attained that speed, rarely seeing much above around 410mbps, but I wasn't overly worried.
Around the start of October I received an email saying that Virgin Media may have an outage in my area as they were performing network upgrades. On the day of the work there were a few brief outages and from the following day, speed tests indicated I was getting around 600-620mbps.
My son mentioned that after the upgrade, download speeds on Steam appeared to be capped at 20MB/s (160mbps) where previously they had often been much higher, often getting close to the speed limit of our connection if nothing else was using the internet in our house. Even worse was the fact that if more than one device was downloading something at the same time, they appeared to share that bandwidth, so two simulataneous downloads, for example one from Steam and another on an Xbox would average around 10MB/s (80mbps) each.
Oddly enough, switching Steam to a different region for downloads appears to give better download speeds. Last night I set Steam to use an Australian server and the download speed was closer to 40MB/s (320mbps). Today I tested downloading the official Windows 11 iso at the same time as downloading a game from Steam and the download speed was hobbled, but as soon as I cancelled the Steam download, the Windows image sped up, reaching over 50MB/s and downloading in less than five minutes.
As another example, I downloaded a 5Gb e-book that I bought as part of a bundle through Humble Bundle. The download started in Firefox and was reporting around 70MB/s. As soon as I started a game downloading through Steam, the e-book download speed dropped down to around 1MB/s and the Steam download was hitting around 19MB/s. As soon as I cancelled the Steam download, the download in Firefox shot back up to 70MB/s again.
I assume that Steam and other providers use content delivery networks, and I'm not sure if the CDN is throttling the data stream or Virgin are doing it, but my tests seem to indicate that it is something Virgin are doing. It does seem odd that this coincided with Virgin's network upgrade.
One final point, all of these connections are on wired connections, not wireless.
I wondered if anyone else has seen similar results following a Virgin network upgrade?
edit - I should also add that this seems to happen with all the major gaming networks that we access - Steam, Xbox Live, Battle.net and Epic Games. Whatever we try to download from these services appears to share the same 20MB/s bandwidth.
