FakeJake

Been lurking on the thread for some time as had nothing of value to input.

But interesting if TCP is affected but UDP is not. There are network settings that can prioritise one protocol over the other. But even without these UDP is faster as it is connectioness whereas TCP is slower but more reliable due to retransmission.

Intuition says there is a box that is struggling and causing many transmission requests slowing everybody affected down significantly using TCP , UDP will not be affected as much but may be losing packets.

Somewhere in the new core routeing is a poorly router (or more than one) may even be a design flaw in a new set of boxes that only becomes apparent when loaded up enough, (pain to find when doing pre go live testing) . .

.

Yes what you've said makes sense and is a possible explanation as to why there's a difference seen when using TCP or UDP.

The hope is that once they've had a proper look at the packet captures, they'll be able to point the finger at what/who is causing the issue and will have data to back that up. I'm looking forward to hearing more.

In reply to a post by SteveBushell999:

I am wondering if something odd is happening to NAT packets? But I have no proof, just a hunch? It's still interesting as NAT isn't just one way of wrapping stuff up (see WIKI) which may explain why I see different behaviour between different routers? More research needed!

The equipment out in the network won't know anything is NATted - that happens on your router and that's the end of the process.

CGNAT?

Not on Zen

... we are led to believe.

What about Cityfibre?

It's not really a "led to believe" thing, CGNAT is easy to spot.

pluralist

If you are looking for more exotic things to go wrong it is more likely something to do with DPI and legal intercept if, as likely, Cityfibre are now big enough to have to implement this for the spooks. (Zen may also be at the size to have to implement things)..

There are several ways to do it that will interfere with throughput noticeably. Occam's Razor suggests core router problems are more likely ( Unless all the people with an issue are using VPNs which could overload the intercept point if the VPN is being intercepted which is a possibility since 24th Feb! )

My bet is still on the BGW between CF and Zen having an issue

Edited by kitcat (Mon 11-Apr-22 20:09:58)

Cityfibre have nothing to do with my connection so I would doubt it's anything to do with them. My connection is delivered via Openreach FTTP.

In reply to a post by kitcat:

My bet is still on the BGW between CF and Zen having an issue

The thread is about speed issues after a GEA backhaul migration from BTW/TTB to Zens own backhaul.

Seeing as that's only relevant over Openreach then the chances of it having anything to do with CityFibre are somewhere between zero and nil.