In reply to a post by richi:

Looks like exponential backoff, which might imply it's a side-effect of packet shaping or some other sort of congestion mitigation. Albeit stupidly implemented.

It's more likely to be an exponential backoff for some retry - e.g. talking to a database or some other associated service. If the first request fails, try 1 sec later, then 3 secs, etc etc until it gives up at 127 secs.

That would make sense.

In reply to a post by jchamier:

In reply to a post by richi:

But on the assumption that 1400 is now the limit for DF packets within Three's core, PMTU Discovery surely will cap at 1400, no?

It should yes, but if that is temporary and becomes 1470, then why limit your modem? Let the system work it out.

In the 1990s and early 2000s we used to set the MTU on our PCs and laptops to 1400 because the PMTU didn't exist in Win98 and similar. There was always strong advice to never change the router, but to set the MTU on the PC/laptop.

Normal MTU discovery relies on ICMP, since so many devices block ICMP it quite often doesnt work, not a good idea to rely on it.

For this reason some OS's have a new TCP based variant which will work but usually is "disabled" by default. It also only fixes TCP not UDP.

e.g.here is the documentation for the linux tunable that controls it.

tcp_mtu_probing (integer; default: 0; since Linux 2.6.17):

This parameter controls TCP Packetization-Layer Path MTU Discovery. The following values may be assigned to the file:

0 Disabled

1 Disabled by default, enabled when an ICMP black hole detected

2 Always enabled, use initial MSS of tcp_base_mss./quote]

Hi All,

Long time no post to this thread... but can anyone who is STILL on three (like myself), confirm that it appears this issue has finally been fixed?

I use Smarty for my primary internet, and it appears I no longer need to use a VPN. Speeds have actually improved overall and they haven't done any work at my local cell as far as I can see.

https://forums.thinkbroadband.com/mobilebroadband/f/...

Perhaps it is is possible for Three to improve their network... I always thought they just ran it further into the ground.

No its not fixed, still have the issue with hanging webpages periodically. Which always coincide with times of excessive high mast contention. I've had RAN Capacity on my mast for over 12 months, Sub 2Mbps after 6pm daily, reported it around 50 times, promised it'll be addressed too many times to count.

The reality is Three are not interested in fixing any issues.

In 3 months my contract ends and I will not be staying with Three.

No, still not fixed. I'm convinced it's to do with their content filtering. I see varying degrees of latency when connecting to HTTPS websites (port 443). On rare occasions I see HTTPS cert warnings in the browser where the wrong cert has been presented (from some entirely different site!!). All these issues can be bypassed by using a proxy such as Cloudflare WARP, however it's not convenient or even possible to run that on every single device on the Network (such as TV's or Google Home, etc).

Has anyone else noticed this problem (or something very similar) returning in the last week? It isn't affecting all websites but seems to be particularly affecting Google and Youtube of the websites that I regularly visit. Like last time, using a VPN seems to get around the problem.

Yes, perhaps a month ago. But it comes and goes.

Mind you, I find it performs better using the three.co.uk APN, so I only use 3internet when I really need an externally-reachable IP address.

In reply to a post by buggerlugs:

No its not fixed, still have the issue with hanging webpages periodically. Which always coincide with times of excessive high mast contention. I've had RAN Capacity on my mast for over 12 months, Sub 2Mbps after 6pm daily, reported it around 50 times, promised it'll be addressed too many times to count.

The reality is Three are not interested in fixing any issues.

In 3 months my contract ends and I will not be staying with Three.

I'm not convinced its high contention.

The reason I say that is my local tower recently got 5G. Had no problems at all for the first month but over the last couple of weeks I started to get page timeouts and network errors. The strange thing is, during the same period an actual download will do 400-600Mbit, so clearly not a contended mast (though upstream being still 4G definitely can be).

When I was on Three 4G the problem there was CLEARLY contention as I would see packet loss and ping spike to insanely high levels. Then again, 4G reception is very rough in the house as theres several houses and trees between me and the mast, which strangely 5G seems to handle better.

Incidentally I tried the MTU tweak and although at first it did seem to help, right now its just as bad.

Can confirm however that changing the APN makes a HUGE difference, suddenly the problem went away and I hit my highest download speed yet.

Edited by alexatkin (Sun 05-Sep-21 03:24:22)