Linked by Thom Holwerda on Mon 21st Aug 2017 22:31 UTC
Internet & Networking

Game downloads on PS4 have a reputation of being very slow, with many people reporting downloads being an order of magnitude faster on Steam or Xbox. This had long been on my list of things to look into, but at a pretty low priority. After all, the PS4 operating system is based on a reasonably modern FreeBSD (9.0), so there should not be any crippling issues in the TCP stack. The implication is that the problem is something boring, like an inadequately dimensioned CDN.

But then I heard that people were successfully using local HTTP proxies as a workaround. It should be pretty rare for that to actually help with download speeds, which made this sound like a much more interesting problem.

The detailed article contains tips to address the problem somewhat.

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Untested feature.
by Alfman on Tue 22nd Aug 2017 04:50 UTC
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So in short, they designed this as a feature to throttle background downloads during games and streaming, but it was rushed and instead of using proper throttling mechanisms that set the TCP window dynamically based on the bytes per unit time, they took a huge shortcut and just hardcoded static TCP windows, as the author does a fine job of explaining.

Hard coding the TCP window results in way too much throttling on high latency links and doesn't do any throttling for the fastest links that have a high probability of consuming all the network resources. This flaw probably would have been discovered with more testing, but apparently it didn't get tested by other developers before it shipped and that was that.

A 7kB receive window will be absolutely crippling for any user. A 128kB window might be ok for users who have CDN servers very close by, or who don't have a particularly fast internet. For example at my location, a 128kB receive window would cap the downloads at about 35Mbp to 75Mbps depending on which CDN the DNS RNG happens to give me. The lowest two speed tiers for my ISP are 50Mbps and 200Mbps.

[Rant On]
Man, we're on a 30/5mbps right now, and we're two tiers higher than the lowest tier! Some might sneer at the 30mbps down, but it's the 5mbps up that really pains me. There promotional pricing for new subscribers isn't half bad, but existing subscribers really get screwed since they won't give us the advertised prices. If I were a governor I would push for a bill outlawing their shit. We just have so much corruption and there's no alternate broadband competition to walk away to.
[Rant Off]

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