Why might a site load faster over a VPN than home wifi network?

September 1, 2023 12:29 PM

I know almost nothing about how computer networks work, but I'm periodically finding that turning on my Mozilla VPN connection will load sites more quickly than if I'm just on the regular home wifi network by Xfinity broadband. This seems intuitive to me, but what do I know?

The only heavy local network traffic that might be happening while I'm working is someone recording to the cable-provided-DVR (I'm not sure how much/how often something's actually being recorded) and sometimes YouTube for music (max 2 hrs a day), but the slow speeds occur when I know that's not being streamed as well. Could that be enough to cause regular slowdowns? Thank you!

posted by smirkette to Computers & Internet (12 answers total)

Best answer: I'd bet that your ISP, Xfinity, is throttling various types of internet traffic for its own ends and can't differentiate between the types when the traffic is going through the VPN so that throttling doesn't happen.
posted by any portmanteau in a storm at 12:45 PM on September 1, 2023 [9 favorites]

Best answer: Check your settings -- Mozilla VPN has built-in ad/tracker blockers. If those are on, things will feel faster because you're not loading a truckload of waste bytes.
posted by humbug at 12:56 PM on September 1, 2023 [7 favorites]

Best answer: I suspect that your computer is using different DNS servers when the VPN is on. That said, it may be a spurious correlation. It's pretty common for something to go wrong on your cable line and end up with intermittent bouts of high latency that manifest as browsing being unusually slow for a few seconds to minutes.

You can check the signal levels on your modem or gateway and see if there are a lot of uncorrected errors or if the levels are way out of whack. If you have one of their XBn devices, type 10.0.0.1 in your browser address bar, log in, then pick Connection and then XFINITY Network on the left. When you scroll all the way to the bottom you'll see a table labeled "CM Error Codewords". Ideally the line that says uncorrectable codewords will be all zeros. If not, reboot your gateway and look again after a few minutes. Get an idea of how quickly they go up when things are acting normally and then check when you're having the slowness. You may see a sudden burst that coincides with the slowness. That indicates some kind of issue Comcast needs to fix.
posted by wierdo at 12:58 PM on September 1, 2023 [1 favorite]

Best answer: You may see a sudden burst that coincides with the slowness.

Sorry, but that would affect the VPN connection just as hard.

The most likely reason the VPN is faster is its server-side junk filtering, plus possibly faster DNS responses.
posted by Stoneshop at 1:09 PM on September 1, 2023 [1 favorite]

Best answer: I started to write a really long, technical thing and then realized I was being boring. So I will skip to the TL;DR.

If your VPN is based in the same POP (point of presence; data center where carriers interconnect) as the servers of the thing you are connecting with, the middle steps connecting you to the stuff you want may be as simple as from one rack of machines to another on the same floor. It makes latency lower and stuff feels much quicker.

Source: I am a telecom exec who talks about this mess all day long.
posted by DirtyOldTown at 1:30 PM on September 1, 2023 [7 favorites]

It doesn't even have to be the same POP/data center. If the number of hops (jumps from POP to POP) is lower in the route taken by his VPN, it will come across as effectively faster, even if eventually delivered over the same home connection.
posted by DirtyOldTown at 1:38 PM on September 1, 2023 [3 favorites]

I dunno, but I'm wondering if this is why my therapist was saying my Zoom was "unstable" while I was on my home computer and not on the work one for a session. I annoyingly had to switch back to using the work computer where people keep interrupting me.
posted by jenfullmoon at 1:48 PM on September 1, 2023

CloudFlare has a sort-of-vpn service that tries to give you a faster route to websites, so it's totally possible that going through a VPN could speed some things up more or less by accident.
posted by BungaDunga at 1:51 PM on September 1, 2023

I am going to guess DNS as well, if only because the answer to strange networking problems is always DNS.

I’ll bet that without the VPN you are using your ISPs DNS, which is possibly not everything it could be.

Your VPN probably routes DNS to better servers.
posted by AndrewStephens at 2:16 PM on September 1, 2023 [1 favorite]

Could also be that your VPN is blocking a lot of trackers and ads. Ad spaces run mini-auctions in their network for what will get displayed, and that can really slow things down. A lot of times VPNs prevent all that from loading.
posted by Bottlecap at 2:23 PM on September 1, 2023

I was going to say the same as DirtyOldTown. If your VPN traffic gets off your ISP fast at the POP because Mozilla has a machine there... Mozilla may have a much faster and better connected internet than your ISP does.

I was on the list for a couple Giga-POPs and a more regular POP. We had like next floor up connections to the likes of Google, Microsoft, Netflix. Better connections, much faster.
posted by zengargoyle at 11:07 PM on September 1, 2023

Your ISP might also be chewing on your DNS queries to shape ad selection, which your VPN isn't going to do.

Many companies also bulk block the worst crapware ads , so those lookups are instantaneous.
posted by wenestvedt at 9:14 AM on September 3, 2023