Ping skyrockets + Packet Loss when Uploading
26-07-2020, 18:48
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#1
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cf.member
Join Date: May 2020
Posts: 36
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Ping skyrockets + Packet Loss when Uploading
I'm posting this on behalf of a friend who I've been having a nightmare playing online games with recently because of his Virgin Media connection.
Essentially, whenever he's doing an upload his ping spikes up massively, and he gets packet loss. These uploads are capped at 1MB/s so aren't maxing-out his bandwidth (in speedtests he gets 12Mbps upload).
See BQM:
You can see at 6pm he has some uploads running and the average pings spike up to the 160ms range. More worryingly, you can see some red packet loss.
I asked him to show me the Downstream and Upstream pages on the router.
Note, the "Pre RS Errors" and "Post RS Errors" were after about an hour from last rebooting the router.
Downstream:
Upstream:
Any idea what the cause of this issue might be? Is this the famous bufferbloat issue on underpowered routers?
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26-07-2020, 21:36
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#2
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FORMER Virgin Media Staff
Join Date: Dec 2010
Location: Warrington
Posts: 4,737
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Re: Ping skyrockets + Packet Loss when Uploading
1MB/s = 8Mbit + overheads, so it doesn't surprise me his ping skyrockets when he's uploading files, if his max upload speed is 12mbit.
But that doesn't sound right, either. What's his actual Virgin package and what's his modem provisioned to? If he's on 100Mb, his max upload is actually 10mbit, not 12. If he's on 200, it should be 20, 350 should be 35. Something doesn't check out.
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26-07-2020, 22:21
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#3
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Dr Pepper Addict
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Re: Ping skyrockets + Packet Loss when Uploading
Presumably the 10M upload is over provisioned, so may read as up to 12 on a speed test.
However, it doesnt matter, uploading at you max speed is going to kill pings, regardless of what that max is.
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27-07-2020, 09:05
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#4
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cf.member
Join Date: May 2020
Posts: 36
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Re: Ping skyrockets + Packet Loss when Uploading
The rule of thumb I'd read is you should cap uploads to 80% of your upload speed, so I just suggested he do a speedtest (which was 12Mbps), then 80% is 9.6Mbps, which was reduced to 8Mbps for some leeway. I will suggest he reduces this even more.
I understand maxing out your download/upload will affect pings, but it surely shouldn't cause packet loss?
This is my home connection (VM 200Mbps), I run PC backups which take a few days to complete. There is no upload bandwidth limit imposed, meaning it saturates my upload bandwidth.
My BQM chart shows rises in ping, but not to the same extreme, and there is no packet loss (my backup finished at 2pm here):
Compare this to my friend's BQM chart, even with a bandwidth limit imposed there are much higher average pings and even some packet loss.
Are the number of "Post RS Errors" on Downstream Channels 1-4 (but not 5-8) normal on my friend's router?
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27-07-2020, 10:48
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#5
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Ran Away
Join Date: Nov 2008
Location: Lincoln
Services: phone + 1gbit BB + SkyQ
Posts: 11,021
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by oscarandjo
Are the number of "Post RS Errors" on Downstream Channels 1-4 (but not 5-8) normal on my friend's router?
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no, you shouldnt be getting the T3 timeouts on the upstream either. Click on reset counters on the post-rs errors and reboot the shub and see what happens.
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27-07-2020, 10:53
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#6
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cf.member
Join Date: May 2020
Posts: 36
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by General Maximus
no, you shouldnt be getting the T3 timeouts on the upstream either. Click on reset counters on the post-rs errors and reboot the shub and see what happens.
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These screenshots were taken about an hour after rebooting the shub, which I believe resets these numbers. But I will continue to monitor it.
What causes these timeouts? The power levels look in-spec (upstream power looks of 48-49 is borderline from what I've read) and SNR looks about right too.
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27-07-2020, 11:09
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#7
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Ran Away
Join Date: Nov 2008
Location: Lincoln
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by oscarandjo
What causes these timeouts? The power levels look in-spec (upstream power looks of 48-49 is borderline from what I've read) and SNR looks about right too.
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48 is mint and mine has been 48 since the dawn of time. There can be several different types of problems with upstream channels which is why there are the 4 different T levels and depending on what the problem is it can impact the downstream and make it looks like there is a downstream fault when there isnt one.
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27-07-2020, 16:23
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#8
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cf.mega poster
Join Date: Jul 2008
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Re: Ping skyrockets + Packet Loss when Uploading
This graph shows my system (170Gb) being backed up to Acronis Cloud between about 02:30 and 04:00 last Sunday morning. (uncapped upload) Upload speed for this backup tends to be in the range 30-45 Mbps out of the over-provisioned 50Mbps I pay for. This is the kind graph profile I would expect from a decently performing connection. I would agree that the graph in the OP isn't satisfactory.
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27-07-2020, 17:16
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#9
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FORMER Virgin Media Staff
Join Date: Dec 2010
Location: Warrington
Posts: 4,737
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by oscarandjo
I understand maxing out your download/upload will affect pings, but it surely shouldn't cause packet loss?
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Are you and your friend both using the same Hub?
Are you both using the hub in hub mode, or router or what?
If so, do you have the same router?
Is your friend actually experiencing packet loss? The TBB graph is only showing that the ping request didn't get a response, this can happen with some setups when the connection is being throttled, as IPMC responses are fairly low in the priority.
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28-07-2020, 23:19
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#10
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cf.member
Join Date: May 2020
Posts: 36
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by Kushan
Are you and your friend both using the same Hub?
Are you both using the hub in hub mode, or router or what?
If so, do you have the same router?
Is your friend actually experiencing packet loss? The TBB graph is only showing that the ping request didn't get a response, this can happen with some setups when the connection is being throttled, as IPMC responses are fairly low in the priority.
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No, we live at different houses, but are just playing video games on the internet together.
Both hubs are in router mode, I have the SH3 and my friend (with the connection problems) has the SH2ac.
Interesting theory about the IPMC responses.
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28-07-2020, 23:25
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#11
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Ran Away
Join Date: Nov 2008
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by oscarandjo
IPMC responses.
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ICMP
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29-07-2020, 14:34
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#12
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Dr Pepper Addict
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by oscarandjo
Interesting theory about the IPMC responses.
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Its not a theory.
Routers treat ICMP (pings) as low priority, so when they get busy, they can end up just ignoring/dropping them.
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29-07-2020, 15:08
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#13
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cf.mega poster
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Re: Ping skyrockets + Packet Loss when Uploading
Quote:
Originally Posted by Paul
Its not a theory.
Routers treat ICMP (pings) as low priority, so when they get busy, they can end up just ignoring/dropping them.
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theory = explanation
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