Buffering issues on Youtube only

[#1]

Hi All,

I wanted to pop together a quick community post to see if anyone else is having similar issues, There's a version of this post over on the BT Forum and EE Forum as well.

Since the beginning of June I've noticed that there's been a measurable increase in videos buffering, streams unplayable and videos downgrading in quality specifically on Youtube. Switching on a VPN instantly stops the issue from occurring. Interestingly it seems to be worse in the evenings but fine in the day.

I have 900mbps FTTP and have no issues whatsoever with speed and connectivity on other sites (streaming such as Twitch, no issues), I have spoken to PN support who have confirmed there's no line issues. I've disabled IPV6 so can rule that out, I've changed DNS so can rule that out. I've tried different devices and the issue persists across multiple devices. I use the PN provided Hub.

YT stats for nerds connection speed
Before connecting to a VPN: 9840 Kbps
After connecting to a VPN: 209389 Kbps

Digging in to the network tab I can see that the issues seem to stem primarily from the rr5---sn-cu-cime7.googlevideo.com GGC server, so potentially may be an avenue of investigation. 

Cheers!

[#2]

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[#3]

Well that's an interesting question.

As an example, at the moment stats for nerds for me gives 58151 Kbps connection speed at the moment (so quite enough for some HD video!).

I occasionally see a low resolution first few seconds on videos but I think that's probably coding by YouTube rather than a bandwidth limitation. 

[#4]

With the VPN disabled is  your traffic being funnelled through a proxy like Norton AV or Apple Relay ?

With the VPN disabled is does your internet connection present the correct Public IP and for the right ISP & Country ?

test with : https://whatismyipaddress.com/

[#5]

Moderators Note

This topic has been moved from Broadband to Full Fibre

[#6]

Same Issue, Just joined Plusnet from EE, On 300mbs Full Fibre and have the same issue, peak evening time about 6500kbps stats for nerds. Have tried ethernet and Wi-Fi with same result. Have changed all DNS to Cloudflare on router and LG Smart TV. When I cast a YouTube video from my iPhone to the TV  at peak time no problems 75-90mbs in stats for nerds. Web browser on TV always gives around 150-200mbs regardless of time of day. PC browser is always giving full 300mbs all day. So issue appears to be YouTube / Google server. Never a problem when with EE. John.

[#7]

Posting a reply to this issue the same as I've done over on the BT Forum.

It's likely a regional issue with a BT GGC cache. It's been dug into in depth on both Reddit and the BT Forum, There's a specific common GGC node that pretty much everyone reporting the issue has shared (***---sn-cu-cime7). The current thought is that BT's google cache server is misconfigured or is struggling under peak load (as it tends to get worse in the evenings).

Somebody ran some packet captures and identified that the specific GGC nodes that present the issue look to have a highly restricted initcwnd parameter that limits connections down to something like 2mb and rather than redirecting the end user to a healthier node it keeps them on that highly restricted one which causes buffering and auto negotiates to lower resolutions.

Seems to be affecting some people in the North West / North Wales / Midlands. This is why using a VPN sidesteps the problem, because you end up on a GGC node other than the affected one that isn't misconfigured.

It's not a DNS problem and won't be mitigated by changing your router. BT need to investigate and I believe its been referred to the correct team via the BT Forum now

[#8]

@JT_400PN You're correct, it's likely a GGC server that BT Operate internally. We did a lot of digging over on the BT Forum and found that affected people are routinely connecting to the ***---sn-cu-cime7 server. Which seems to be struggling at peak times and appears to be misconfigured as it throttles down connection speeds to something like 2mb rather than failing over to a healthier node. You can side step it by using a VPN, or blocking the specific broken node at a firewall level until they fix it.

If it helps alleviate any switching concerns, You'd have had this problem on EE and BT based on your region, it's a BT infrastructure issue that needs investigating.

[#9 · Accepted solution]

They've confirmed over on the BT Forum that it was misbehaving caches. It might still affect some people but now they've taken the bad caches out you'll fail over to healthier ones, it might take a little while but it should correct itself soon.