Increase in latency after change of backhaul

The latency shown on the BQM for my connection has increased from just over 15 ms to almost 25 ms after the backhaul being used was changed to TTB this week. Does this sound correct, as I thought the increase was normally only a few milliseconds?

My average RTT to Quad9 is between 11 and 12ms on Zen FTTC

25ms sounds only a tad high but on the other hand, the difference between your old and new figure is less than 100th of a second or about the time taken for Usain Bolt to run 10 centimetres (4 inches), so whether or not it really matters is something to consider

In reply to a post by tboorman:

The latency shown on the BQM for my connection has increased from just over 15 ms to almost 25 ms after the backhaul being used was changed to TTB this week. Does this sound correct, as I thought the increase was normally only a few milliseconds?

Change of backhaul usually results in a DLM reset.

If you're on FTTC and an ECI cabinet that would result in Interleaving being applied, adding 8ms automatically.

Edited by j0hn83 (Mon 23-Aug-21 09:22:24)

Thanks, I am on FTTP.

I raised this with Zen's support, and this is the reply that I got:

I am sorry to hear about the latency spike since the backhaul change, the equipment change is periodic and for the long term good. 25m/s is not considered an fault or abnormal condition, this occurred due to the change in route from what it use to be- the route selection process is automatic and can not be changed manually.

If you are south of somewhere like Birmingham that sounds like you used to go direct to London but now go via Zen in Manchester then down to London.

I am in South Wales, but I thought that would show up in a traceroute output. The first hop after my router is vt1.cor2.lond2.ptn.zen.net.uk.

I raised this topic the other day because it appears my traffic is being routed from Bristol up to Manchester and then back down to London. I've emailed them but haven't had a response yet.

https://forums.thinkbroadband.com/zen/f/4692293-chan...

If it's automatic, what is it based on? Can't be latency, possibly load balancing? Either way, I know it's fractions of ms, but I do an awful lot of gaming and I can't see how they can have a page like below if they're then routing you sub-optimally.

https://www.zen.co.uk/broadband/gaming-broadband

With PPP connections like xDSL, the L3 path your traffic takes doesn't show up before the first hop which is where the PPP terminates, so you might not always have a clear idea about geography merely from a traceroute.

Also Manchester is pretty well connected internationally in terms of Internet exchanges and peering so I wouldn't necessarily worry about thinking you need to reach "back down to" London to do anything useful.
And if you are talking to anything in the USA or beyond you'll likely see >100ms anyway.

Whereas with FTTP I don't know if address assignment is any different or you still do as PPPoE.

With fibre leased lines (whether fibre or copper presentation) it is generally a static /29 subnet and no PPP nor authentication.

Edited by prlzx (Mon 23-Aug-21 22:27:14)

After a reboot of my router, the latency has gone down to 18.5 ms.