Is it normal for uploads on ADSL to make the connection unusable (> 4000ms latency)?

3

I have an ongoing saga with my internet connection; where the latency periodically goes through the roof. In most cases, this seems to coincide with something uploading data.

I'm not having a lot of joy with the ISP (Sky), so I'm trying to do my best to gather information that might help. First off, I need to figure out if this is normal. I don't remember ever having this sort of problem in previous properties; but our phones didn't back up every photo/video recorded then (and we didn't have kids, so there were less of them!).

It's an ADSL connection; downstream is 11Mbs, upstream is 1Mbs. The usual culprit is Google+ on Android doing AutoBackup of photos + videos.

Here is a graph of ping times to the router, google.co.uk and sky.com for 20 minutes. The first 10 minutes there was nothing uploading (just some general surfing, and background chatter from a PC, two smartphones, two tablets). The second 10 minutes is during an auto-backup of a video to Google+ (which seems to take far longer than I would expect).

Timeout was set to 5 seconds; and all timeouts are recoded as 10000 in the data (so they go off the top of the chart). Both Green (Sky) and Red (Google) lines are pretty consistent, so the red line is mostly obscured by the green. The blue line has only one ping that was high at 2000ms.

The problem obviously isn't just that ping returns high numbers; the connection is utterly unusable during this time.

Ping times

Raw data is available here: https://gist.github.com/DanTup/800e72d05adf8a0a5cef

Is there something wrong; or is this normal for ADSL? I can imagine that Google might be able to receive my data faster than my line can transmit it and saturate the upstream; but I would expect people to generally be unhappy with ADSL if this was normal?

If it's not normal; any further tips on providing info that might help Sky investigate/fix it would be welcome.

Here are some router stats if they help. The initial line testing (DLM?) started at 2Mbs and went down, so someone at Sky manually set us at 11-12Mbs/1Mbs based on these stats.

Router stats

(Posted to Sky forums too)

Edit: Video

http://youtu.be/0V1TGfCnsKc

Danny Tuppeny

Posted 2014-11-18T17:14:22.420

Reputation: 2 249

Upload is used to send ACKs (among other things), TCP performance will go all to hell if it can't send ACKs reliably. Can you limit the uploads? – NickW – 2014-11-18T17:19:30.253

I've seen this. you can test with jperf to confirm. You gotta limit the uploads or get a better line... – BlueCompute – 2014-11-18T17:24:24.080

Short answer (although not helpful at all) - nope. This is definitely not normal. What is even more discouraging, is the fact that your line parameters looks good enough. Does your ADSL lose the carrier and reconnect often ? Not sure from these pictures. – drookie – 2014-11-18T17:25:05.703

1It's entirely normal if you're saturating the line, it's not difficult to do. – NickW – 2014-11-18T17:25:46.543

@EugeneM.Zheganin No, it doesn't often disconnect; though we sometimes restart the router trying to fix it. I wondered if the initial testing gave poor speeds due to some issue, and manually setting it to 12Mbs sort-of ignored this issue? – Danny Tuppeny – 2014-11-18T17:26:14.150

I used to work in an ISP, and watch people saturate their upload, and the result was this. Whether its normal on Sky, or ADSL in general, I wouldn't want to say. – NickW – 2014-11-18T17:34:50.780

Well... playing with the physical channel speed should give you results only in the case of bad media (rotten copper lines and stuff) - which causes lots of line encoding errors and frequent loss of carrier. If you don't suffer from those (CD can be checked not only from the web page, but, more fast, from it's indication on the box - usually fast blinking means the CD is lost, slow blinking means training, and steady light means CD is on) - your line should behave fine within the US/DS range. – drookie – 2014-11-18T17:35:04.127

I actually agree with @NickW . Checking if you're saturating your line is easy, although I'm not sure it's evident from the screenshot (which I'm not sure I understand at all). – drookie – 2014-11-18T17:36:42.610

The only way you'll be able to tell if the line is saturated is output from the router itself (SNMP for example), or from something upstream (DSLAM, which the ISP will have access to). You could also put a firewall behind your router, that would allow you much more info (and control) on the traffic flowing from your LAN to the internet. – NickW – 2014-11-18T17:41:45.353

@NickW None of that sounds "easy" ;( How reliable would performing an upload from the PC and monitoring the rate be? If it's roughly same as the ADSL upstream, it's saturated? – Danny Tuppeny – 2014-11-18T17:42:58.370

Nope, your SLA could be even less, and the speed can be shaped by the ISP equipment, not by the channel speed. – drookie – 2014-11-18T17:44:58.750

You can measure if the US is saturted by uploading something big limiting the speed from your side on the application level, and measuring the icmp loss rate and it's reply timings. If these won't correlate with the upload speed (I guess it's the US that's saturated) then you have some line/ISP problem. – drookie – 2014-11-18T17:50:19.073

@EugeneM.Zheganin At uk.testmy.net/upload I got a reported 921Kbps which isn't far from the 1082kbs the router says. Does that seem high enough to be saturated? (Though this was an upload test; obviously might not be the same that Google+ is doing). – Danny Tuppeny – 2014-11-18T17:50:26.827

Yup, looks like the upper limit. – drookie – 2014-11-18T17:50:56.140

@EugeneM.Zheganin So; this is likely normal and unfixable without me sticking some sort of traffic shaping around my router? :( – Danny Tuppeny – 2014-11-18T17:53:43.257

If this is the point where the latency increases greatly and the packet loss happening - yup. But there's hope - you clearly have an Annex A equipment, you can ask your ISP if Annex M is supported, - if yes - then your US can be upgraded (unfortunately, only with your router probably). You can also use various QoS techniques to prioretize some kinds of your traffic. – drookie – 2014-11-18T18:16:06.673

This link suggests there is no Annex M :( http://helpforum.sky.com/t5/Broadband-Talk-questions/Can-I-improve-my-upload-speed/qaq-p/2132189 And I'm not sure if more US would help; unless I could beat Google+'s? ;(

– Danny Tuppeny – 2014-11-18T18:24:15.787

I got to talk to a techie at Sky today, who said this is not normal at all (see answer). I also uploaded a video showing the issue a bit better http://youtu.be/0V1TGfCnsKc

– Danny Tuppeny – 2014-12-04T22:42:31.083

Answers

0

Today Sky support let me talk to a techie, who said no, this is not normal. It is (as expected) normal for ping to rise; but not for the connection to be completely unusable. They can't see any faults or explanation. There's no noise on the line, error rates are low, etc.

They're sending a new router, and the investigation will continue if that does the same (which I suspect it will)!

Danny Tuppeny

Posted 2014-11-18T17:14:22.420

Reputation: 2 249

did a new router help? – Crummy – 2018-10-14T21:37:07.487

It's been a long time so I don't remember the details, but Sky did some tweaking of things and then at some point Fibre came along and we changed ISP. We've been on fibre (80/20) since and not had any issues like this. – Danny Tuppeny – 2018-10-15T06:42:09.080

1

The problem is widespread enough that it even has a name. It is most frequently seen on the upstream, this is likely due to the upstream bandwidth being lower than the downstream bandwidth. The phenomena can happen on any link, but it requires more effort to get the problem on a fast link.

How much extra latency you get depends on various factors. I have observed this cause only 100ms of extra latency in some installations and as much as 60s of extra latency in others. It is not ADSL specific, my observations has mainly been with docsis modems.

If you feed all your traffic through a router that you control before it enters the modem, you can throttle traffic on the outgoing port on the router before it reaches the modem. If you throttle the traffic to 90% of the uplink capacity, you shouldn't see any latency caused by the modem.

There is no guarantee the router is going to do any better. But at least you can chose a router that can do it properly.

kasperd

Posted 2014-11-18T17:14:22.420

Reputation: 2 691

Asked: 2014-11-18T17:14:22.420

Viewed: 529 times

Active: 2014-12-04T22:41:42.040