Bufferbloat upload latency

Firegod

Firegod

Firegod

Soldato
Joined
12 Sep 2003
Posts
11,205
Location
Newcastle, UK
Hey :)

So my brother on a fixed line broadband package is having terrible latency on his upload data. It is repeatable and consistent. His download latency looks fine to me.

He uses his ISP modem in bridge mode and has a pair of Asus ATX9 nodes. The nodes are wireless backhaul. He has tested from his PC via WiFi and from his phone, on both 5Ghz and 2.4Ghz bands, and from both nodes. ISP router hasn't been rebooted in a few months.

He has QoS enabled as such, which I thought being enabled would help with bufferbloat? Unless this ordered list needs adjusting in someway?

IMG-20250527-WA0005-2.jpg


His result is shown below.
IMG-20250527-WA0013-2.jpg


We both have to use WiFi calling due to poor signal indoors and often the call will go silent or one person will stop hearing the other. I can only assume that this latency is part of the problem.

I'm just wondering what else to do to try and improve this? He tried data from his phone and the figures were much improved. I thought about getting on to his ISP then thought, hang on, would they have any clue about this lol.

Cheers.
 
Sorry just heard he has rebooted the hardware. No difference. He has also tried reordering the QoS preset list and in addition, turned the settings off. No difference. Is this a line problem? Or is the ISP hardware at fault?
 
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Could be an MTU problem? Especially if he's not using the ISP's provided router and has left things set to default, depending on how his internet connection is encapsulated etc. Is it PPPoE?

kb.netgear.com

Ping Test to determine Optimal MTU Size on Router

Use the command prompt to send large packets of data outbound, gradually trying smaller packets until you get a positive reply to determine the optimal MTU size.
kb.netgear.com kb.netgear.com
 
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Bufferbloat is an issue on networks under load, if the only thing on there is a phone making a Wi-Fi call then bufferbloat won't be the reason the quality is bad.
 
Sinbad2000 said:
Could be an MTU problem? Especially if he's not using the ISP's provided router and has left things set to default, depending on how his internet connection is encapsulated etc. Is it PPPoE?

kb.netgear.com

Ping Test to determine Optimal MTU Size on Router

Use the command prompt to send large packets of data outbound, gradually trying smaller packets until you get a positive reply to determine the optimal MTU size.
kb.netgear.com kb.netgear.com
Click to expand...
Sorry to clarify, he is still using the ISP hardware, but in bridge mode. Then the Asus XT9 node is connected to that. :) I believe his broadband is copper back to fibre at the cab. So would that be PPPoE? Sorry I don't know much about that sort of thing as I use mobile broadband so I'm more used to talking about APNs and Bands and Cell Towers etc. :)
 
Caged said:
Bufferbloat is an issue on networks under load, if the only thing on there is a phone making a Wi-Fi call then bufferbloat won't be the reason the quality is bad.
Click to expand...
Understood thanks. I just meant when I do call him, we have this issue (not sure at the time what else he might be doing. Might have his PS5 on the go or streaming etc). I just made mention as I wonder if at those times, this upload latency could be the cause. Anywho, the mobile phone thing isn't that important (probably shouldn't have made mention lol). I'd like to try and know what is causing this high upload latency for him. Even for me, on mobile broadband if I test from my PC over WiFi, I fair better than he does. And I don't have any sort of QoS features to enable.

Bufferbloat.jpg


I'll get him to test with an ethernet cable. :)
 
Firegod said:
Sorry to clarify, he is still using the ISP hardware, but in bridge mode. Then the Asus XT9 node is connected to that. :) I believe his broadband is copper back to fibre at the cab. So would that be PPPoE? Sorry I don't know much about that sort of thing as I use mobile broadband so I'm more used to talking about APNs and Bands and Cell Towers etc. :)
Click to expand...
Yeah I got it was in bridge mode but in that mode it's not really doing anything on the internet connection, just acting as a physical connectivity bridge.
The XT9 will have some kind of configuration set up on its WAN port - but before you dig into the weeds of that, have a go at the MTR testing I linked to, find the optimal value, and then see if you can find an MTR setting in the XT9's config and make sure it's set to the same value.
 
Sinbad2000 said:
Yeah I got it was in bridge mode but in that mode it's not really doing anything on the internet connection, just acting as a physical connectivity bridge.
The XT9 will have some kind of configuration set up on its WAN port - but before you dig into the weeds of that, have a go at the MTR testing I linked to, find the optimal value, and then see if you can find an MTR setting in the XT9's config and make sure it's set to the same value.
Click to expand...
OK will do. Appreciate it. :)
 
The QoS on the Asus router probably has somewhere that you can tell it your internet connection speed, if you do a speed test with QoS turned off and nothing else on the network doing anything, take 2Mbps off the number you get and set that as your upload speed. So if you do a speed test and get 18Mbps up, tell the router your upstream is 16Mbps.

It would also be good to get an understanding of the connection and what device is doing the bridging (and to make sure it's only doing that). From the speeds it looks like a well performing FTTC.
 
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Bufferbloat is a little like optimal air flow in a case. It's a bit of a black art.
I spent some time with my ISP complaining about upload buffer bloat, which increased my latency by more than a factor of ten. The conversation went nowhere and I solved the issue using QOS (Cake) and artificially setting the bandwidth to a little less than the service speed. But, very interestingly, a few years later when I renegotiated my broadband deal with the same company, I increased the service from 300mbps to 500mbps and the bufferbloat completely disappeared. I don't use QOS any more and don't set the service speed artificially low and it all works perfectly well. I can only assume that the bufferbloat was down to my ISP.
Anyway, first thing to do is find out whether the problem is you or your ISP. Use a cable. If the problem is still there, then it's probably your ISP, if it's gone then it's you.
 
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Caged said:
The QoS on the Asus router probably has somewhere that you can tell it your internet connection speed, if you do a speed test with QoS turned off and nothing else on the network doing anything, take 2Mbps off the number you get and set that as your upload speed. So if you do a speed test and get 18Mbps up, tell the router your upstream is 16Mbps.

It would also be good to get an understanding of the connection and what device is doing the bridging (and to make sure it's only doing that). From the speeds it looks like a well performing FTTC.
Click to expand...
Winner.

He has changed it from auto to manual (QoS) and fixed the speed as suggested. Here is the new result. Upload latency has much improved!

Bufferbloat.jpg
 
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