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Author Topic: High packet loss on Virgin  (Read 32588 times)

Ronski

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Re: High packet loss on Virgin
« Reply #135 on: June 23, 2020, 10:12:27 AM »

Good job I'm not paranoid  ;)
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exdirectory

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Re: High packet loss on Virgin
« Reply #136 on: October 09, 2020, 09:39:19 PM »

Sorry to open an old post but I think I may have this same issue for many months.

Attached is a typical day on my BQM.

I used to have Virgin SH3 Modem mode -> pfSense -> LAN, but every hour or so we used to lose the internet for 60 seconds, very frustrating!

I then switched to Virgin SH3 Router mode -> pfSense -> LAN, no full drop outs anymore but still get these spikes on BQM. If I check my neighbours BQM it is a perfect graph.

If I have understood this thread correctly... having lots of LAN traffic can overload the DNS and cause SH3 some issues and hence when BQM is pinging it, it is then slow to respond and hence you see the spikes. This also can affect outgoing LAN->WAN traffic. By changing to DNS Forwarder, pfSense is caching DNS entries and therefore less load on VM DNS, one step further is not to use VM DNS, then problem goes away?

Is this still the correct way to go now on 2.4.5 p1

Or have I completely missed the point?

I was on 2.4.4 p3, this evening i upgraded to 2.4.5 p1. Then I found this thread while googling.
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PhilipD

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Re: High packet loss on Virgin
« Reply #137 on: October 10, 2020, 10:13:09 AM »

Hi

pfSense caches all DNS requests in DNS resolver mode, so will a PC and most other devices after the first request so there simply isn't that much DNS traffic on a typical network and very few packets. 

If you go into pfSense, select pfTop in Diagnostics, and under the filter expression type 'port 53' to view all DNS traffic going in and out, you will see how much traffic there is related to DNS, on my network with lots of devices there can be lots of requests but they are just a few packets and over and done with in a split second before the firewall times them out after 30 seconds or so, and fewer still tend to go out to the wider Internet, with a lot being resolved from the pfSense DNS cache.  Compared to all the other traffic going in and out, DNS is just a very tiny fraction of data, and to the router, VM modem and their network, a DNS request is no different to anything else.

So I'm not sure why the forwarder mode would make any difference, however there is a bug with pfSense when the DNS Resolver is enabled in that it keeps reloading if the option 'Register DHCP static mappings in the DNS Resolver'  is checked (under Servers - DNS Resolver) this can cause some down time when DNS isn't being resolved and makes pfSense a bit busy for a bit especially where you have other packages installed that also restart because that.

Your chart looks typical really for Virgin Media really, was your neighbours chart also from Virgin Media?
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adhawkins

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Re: High packet loss on Virgin
« Reply #138 on: October 10, 2020, 11:15:28 AM »

Hi,

That chart is not typical of VM.

I'd try making the changes above, enabling forwarder mode in the resolver, and turning off the registration of DHCP addresses. This made a huge difference for me.

Andy
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PhilipD

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Re: High packet loss on Virgin
« Reply #139 on: October 10, 2020, 11:30:09 AM »

Hi,

That chart is not typical of VM.


All the ones I've seen have loads of yellow and blue, I've yet to see one mostly green :-)

There must be something seriously wrong with VMs network if it is going wonky because of the small amount of traffic from DNS requests to authoritative servers.

Regards

Phil

 
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Ronski

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Re: High packet loss on Virgin
« Reply #140 on: October 10, 2020, 11:41:09 AM »

@exdirectory your graph doesn't look to bad compared to how mine was at the start of this thread, shame I can't still see them. Anyway the advice in this thread certainly vastly improved my graphs and experience.

This is what mine looks like on a good day without much use.

https://www.thinkbroadband.com/broadband/monitoring/quality/share/7a9583a419a7a17c5a125902d2ec2a7bc4c67481-05-10-2020

And here with some use.

https://www.thinkbroadband.com/broadband/monitoring/quality/share/8c6b0e7cea7c5b1f06a8e28219c8cfe09cd3ca24-07-10-2020

@PhillipD

It isn't so much as Virgins network it was something to do with the combination of pfSense and the Super Hub in modem mode, mine was horrendous and it also affected browsing. Switch the hub to router mode and it was perfect, well as perfect as Virgin can be. I even used a ZyXEL router and the hub in modem mode and it was perfect, switch back to pfSense and it went bad, the changes suggested in this thread vastly improved it. It seemed to be related to a hub firmware update in January /February can't remember the details.


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exdirectory

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Re: High packet loss on Virgin
« Reply #141 on: October 10, 2020, 02:59:08 PM »

I have two different neighbours graphs attached...
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exdirectory

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Re: High packet loss on Virgin
« Reply #142 on: October 10, 2020, 03:01:59 PM »

IMO, they are both quite a lot better than mine.

Note that I am the only one running pfSense, they are just using SH3 as normal.

So my next step then is to "enabling forwarder mode in the resolver, and turning off the registration of DHCP addresses"

Should I go back to modem mode first though?

As I have wifi off on router mode, what  do I benefit from being in modem mode, I am only running pfSense in vanilla with DHCP server enabled.

Should I change from using VM DNS servers or is that not relevant?

Also, my pfTop port 53 graph attached in case anyone spots anything odd there

« Last Edit: October 10, 2020, 03:06:46 PM by exdirectory »
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exdirectory

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Re: High packet loss on Virgin
« Reply #143 on: October 10, 2020, 03:07:07 PM »

pfTop
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PhilipD

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Re: High packet loss on Virgin
« Reply #144 on: October 10, 2020, 03:48:06 PM »

I rest my case, nothing good about those either :) Latency ups and down on Virgin are all part and parcel of their network.  Yes their charts might be better than yours, but all of them aren't exactly what you would want to see.  A snapshot of mine is at the post here https://forum.kitz.co.uk/index.php/topic,24600.msg414550.html#msg414550.

Nothing on pfTop that is out of the ordinary that I can see, just standard DNS lookups using a tiny tiny amount of data as expected.  DNS is about as light weight as you can possibly get for internet traffic that does anything meaningful, just a bit above that of a ping.  If you do pfTop again and this time filter by 'proto icmp' you will probably see more pings constantly from Thinkbroadband and other things on your network than you do DNS requests going out.

I'm not sure what exactly the issue is but it is odd that DNS is causing a particular issue as 99% of the time the network isn't making DNS requests, they are just extremely fleeting and they are just ordinary data packets, so something fishing going on with their network.  What happens to the graph if you disconnect everything so it is just pfSense connected to the WAN, where there will be no DNS requests being made, are you still seeing the issue?

It would be interesting to see if the same problem happens with a PC on the network doing DNS Resolution and not pfSense and is the same latency issues observed, that way it rules out pfSense, and rules in something Virgin is doing when it detects DNS packets going straight out to authoritative servers, i.e. maybe the modem is inspecting DNS packets going out direct to the internet to record what the requests are, perhaps to keep a record of what sites are being visited to supply the data should they get a court request to.  There is more to this than meets the eye I think.

Edit: Okay perhaps it is something related to checks they do, maybe they deliberately throttle DNS packets going to the wider internet on the assumption they are or could be malicious or staging a Denial of Service attack, maybe their throttling when it turns just works by slowing down small packets so ends up affecting pings as well, with popular DNS caching servers like Google etc being whitelisted.

https://www.virginmedia.com/help/open-dns-resolver-vulnerability-alert

Regards

Phil
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j0hn

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Re: High packet loss on Virgin
« Reply #145 on: October 10, 2020, 04:53:48 PM »

Your chart looks typical really for Virgin Media really, was your neighbours chart also from Virgin Media?

The vast amount of yellow is typical, but the recurring very high yellow peaks are not.
They are caused by pfsense running in resolver mode, nothing more.
Switching a Virgin Hub to router mode immediately removes the high peaks.
Switching pfsense to forwarding mode does the same.

Going by this thread and a thread on the Virgin forums it's something that seems to effect all Virgin lines running pfsense is resolver mode but it only seems to effect Virgin lines.

The difference between my Virgin (FTTP/RFOG) line and my OpenReach (FTTP/GPON) line is laughable. The BQM's are night and day.

20ms base latency and about 10ms constant jitter on Virgin.
13.8ms base latency on OpenReach with zero jitter. A tiny amount of sporadic yellow during high usage.
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exdirectory

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Re: High packet loss on Virgin
« Reply #146 on: October 10, 2020, 05:19:10 PM »

What happens to the graph if you disconnect everything so it is just pfSense connected to the WAN, where there will be no DNS requests being made, are you still seeing the issue?

Good test, will try that overnight and share the BQM.

I will change one thing at a time, but what about these?

1, Should I go back to modem mode first though?

2, Should I change from using VM DNS servers or is that not relevant?
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niemand

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Re: High packet loss on Virgin
« Reply #147 on: October 10, 2020, 05:52:05 PM »

Those BQMs all look like the Virgin network serving you is quite heavily loaded.

Not critical but notable.
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PhilipD

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Re: High packet loss on Virgin
« Reply #148 on: October 10, 2020, 05:52:50 PM »

They are caused by pfsense running in resolver mode, nothing more.

But why?  What is the difference between sending a DNS request to a DNS forwarder as opposed to sending a DNS request to an authoritative server?  How can that cause higher latency and only on Virgin?  DNS requests leave pfSense periodically, it's tiny amounts of data, they last mere milliseconds, how can that have an effect on latency on incoming pings that also happen periodically a few times a second that also last milliseconds?

Something else is going on here, and a good test would be to run a DNS resolver elsewhere on the network to see if that triggers the same latency issues to rule out or in pfSense involvement, or perhaps someone has already.

Quote
The difference between my Virgin (FTTP/RFOG) line and my OpenReach (FTTP/GPON) line is laughable. The BQM's are night and day.

20ms base latency and about 10ms constant jitter on Virgin.
13.8ms base latency on OpenReach with zero jitter. A tiny amount of sporadic yellow during high usage.

Is this due to being oversubscribed or just typical of DOCIS? 

Edit: I just ran DNS Benchmark from GRC.com which makes hundreds and thousands of DNS requests to dozens of DNS servers including pfSense DNS resolver to see which is fastest.  With all that going on I had pings running to bbc.co.uk and thinkbroadband.com and they didn't change in anyway.  I see nothing on the BQM chart that indicates this test was run.  The benchmark showed that the pfSense resolver was the fasted by some margin, hardly a surprise, and worked 100% without error.

So DNS itself is transparent to the BQM, no matter how hard you try to flood the network with requests, so something else is going on here, it's not the DNS requests themselves causing a problem, but something they are triggering.

Regards

Phil
« Last Edit: October 10, 2020, 06:05:28 PM by PhilipD »
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j0hn

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Re: High packet loss on Virgin
« Reply #149 on: October 10, 2020, 06:17:27 PM »

Something else is going on here,

Indeed. Not necessarily pfsense at fault, that's not what i was suggesting.
It only happens with pfsense and Virgin lines using the Hub in modem mode.

Quote
Is this due to being oversubscribed or just typical of DOCIS?

Just typical of DOCSIS.
I was 1st on our very large Virgin cabinet in a brand new build area.
The BQM was full of yellow (every minute of every day) and the line suffered poor jitter from the moment it went live till i ceased the service a couple weeks ago
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