Highly variable latency on Zen FTTC

I moved from Virgin to Zen a few weeks ago and I've noticed a distinct difference in the BQM graphs. On Virgin, the graph background was mostly black, indicating a low maximum latency, whereas with Zen, the background is almost entirely yellow, indicating very high maximum latency. There's an example of my Zen IPv4 BQM graph here. My IPv6 graph is very similar.

The variable latency is also evident on an outbound ping test. Here's a typical example while my FTTC connection is almost idle:

$ ping -c 5 www.bbc.com
PING www-bbc-com.bbc.net.uk (212.58.244.71) 56(84) bytes of data.
64 bytes from bbc-vip116.telhc.bbc.co.uk (212.58.244.71): icmp_seq=1 ttl=54 time=8.37 ms
64 bytes from bbc-vip116.telhc.bbc.co.uk (212.58.244.71): icmp_seq=2 ttl=54 time=8.93 ms
64 bytes from bbc-vip116.telhc.bbc.co.uk (212.58.244.71): icmp_seq=3 ttl=54 time=316 ms
64 bytes from bbc-vip116.telhc.bbc.co.uk (212.58.244.71): icmp_seq=4 ttl=54 time=49.8 ms
64 bytes from bbc-vip116.telhc.bbc.co.uk (212.58.244.71): icmp_seq=5 ttl=54 time=8.81 ms

--- www-bbc-com.bbc.net.uk ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4004ms
rtt min/avg/max/mdev = 8.373/78.423/316.098/119.903 ms

I'd appreciate guidance on whether this is normal for a Zen FTTC connection or whether it indicates a fault somewhere. I'm using a Vigor 130 modem into a pfSense router/firewall. The only hardware difference, compared with my time with Virgin, is that the Virgin hub has been replaced with the Vigor modem (and, of course, that I'm using an Openreach line).

The variable latency isn't causing me any problem and I'm happy to accept it if it's normal, but I'm curious about the cause and whether it's to be expected with an OR line and Zen..

Edited by ashdown (Wed 11-Dec-19 19:52:38)

your graph isnt normal for any isp never mind zen. Its consistent 24/7 suggesting the problem is with your equipment somewhere.

Oh my giddy aunt. I have never seen a graph like that.
As Chrysalis has said, the issue has to be at your end. I'm with Zen on FTTC and have never seen a graph that come remotely near to resembling yours @ashdown.

This is what i normally see, that's with a half mile walk to the cab.

https://www.thinkbroadband.com/broadband/monitoring/...

Edited by kitfit1 (Sun 15-Dec-19 15:56:06)

Last time I saw something like that was due to torrenting and constant uploads saturating the available bandwidth

Thanks to you all for confirming that this isn't usual. There's no torrenting or significant uploading going on.
I'll have to investigate further, perhaps by changing the Vigor 130 modem as that's the only new hardware introduced on the switch from Virgin.

In reply to a post by ashdown:

Thanks to you all for confirming that this isn't usual. There's no torrenting or significant uploading going on.
I'll have to investigate further, perhaps by changing the Vigor 130 modem as that's the only new hardware introduced on the switch from Virgin.

I'm also using a Vigor 130 modem and would be very surprised if that was the issue. I'm guessing your router is the most obvious problem, it may well need reconfiguring after the move from Virgin.

I've also seen a similar BQM on a badly configured router which had an open DNS resolver and similarly, the upload bandwidth was being completely saturated.

Thanks for all the suggestions but it does seem that the Vigor 130 modem is the culprit. I first tried rebooting it, but that had no effect on the issue. I then reset it to factory defaults and the effect was quite dramatic:

BQM showing before and after the reset

This is still showing latency spikes which are a little higher than I 'd expect, but the multi-hundred-millisecond delays have all gone and I'm now seeing low and very consistent RTTs on outbound pings. I'm mystified by this: the Vigor 130 was brand new a few weeks ago and I'd changed nothing on it - no configuration changes at all since new. So a reset to factory defaults shouldn't have done anything, although it clearly has.