Kitz Forum

Broadband Related => FTTC and FTTP Issues => Topic started by: timeless on February 28, 2019, 09:46:27 PM

Title: MTU settings (Sky fibre Max)
Post by: timeless on February 28, 2019, 09:46:27 PM
l did find a similar thread on the subject and from all information lve found my suggested MTU limit should be set at the default of 1500 (which is set on both my router and modem) however my PS4 reports ip fragmentation issues which l want to try resolving.

l had changed it in the past to 1400 which improved my speed tests and the maximum l get a reply on is 1472 which would suggest from what lve read that 1500 should be correct but this lowers my download speeds significantly when downloading from the service, hence lm looking for the optimal setting in order to get the best speeds for both downloading games/updates and online gaming.
Title: Re: MTU settings (Sky fibre Max)
Post by: Chrysalis on March 01, 2019, 02:51:42 AM
I dont get fragmentation reports with 1500 mtu on my ps4, just NAT issues.
Title: Re: MTU settings (Sky fibre Max)
Post by: timeless on March 01, 2019, 03:04:43 AM
setting to auto does get rid of the message, but my download/upload drops quite a bit for some reason.
Title: Re: MTU settings (Sky fibre Max)
Post by: Chrysalis on March 01, 2019, 04:39:51 AM
Ok I meant its 1500 on my firewall/router, I dont think I adjusted the PS4 setting so thats on whatever its default is.
Title: Re: MTU settings (Sky fibre Max)
Post by: timeless on March 01, 2019, 08:35:46 AM
lm pretty sure the default is 1500 when its set to auto.
Title: Re: MTU settings (Sky fibre Max)
Post by: j0hn on March 01, 2019, 09:42:13 AM
lm pretty sure the default is 1500 when its set to auto.

Not quite.
When set to Auto on the PS4 the maximum MTU is 1500.

I've never changed my PS4 MTU and I wouldn't recommend anyone to do so.

My advice is set the PS4 to Auto and leave it alone.
Title: Re: MTU settings (Sky fibre Max)
Post by: Alex Atkin UK on March 01, 2019, 12:28:20 PM
I think in the early days I did have to change the PS4 setting once, but I think it was a temporary glitch on PSN.

I believe PS4 may still benefit from using a proxy server on the LAN to speed up downloads.  Never understood why but it used to make a HUGE difference on PS3.  I never bothered to test when I got the PS4 Pro, its on defaults.
Title: Re: MTU settings (Sky fibre Max)
Post by: Chrysalis on March 01, 2019, 06:37:31 PM
yeah generally speaking I dont suggest tuning mtu on client devices unless for diagnosis temporarily, if it needs to be changed it should only ever be done on the firewall/router.
Title: Re: MTU settings (Sky fibre Max)
Post by: timeless on March 01, 2019, 07:55:33 PM
l still dont get why my speed halves while set to auto, normally l download between 50/60meg down or at least thats the network test result, and then in the high teens for upload, since returning to auto l barely reach 25 me down and 6 meg up, and these are consistent results which is one of the reasons l felt it worth investigating.
Title: Re: MTU settings (Sky fibre Max)
Post by: Alex Atkin UK on March 01, 2019, 11:23:01 PM
Is that the PS4 speed test as I think its known to be pretty inaccurate?
Title: Re: MTU settings (Sky fibre Max)
Post by: Weaver on March 02, 2019, 10:56:50 AM
There’s something very funny going on, because unless someone is sending packets that are oversized and so getting fragmentation, then tweaking MTU values should never cause speed differences that are other than very small.

Try using the test download files of different sizes at https://www.thinkbroadband.com/download (https://www.thinkbroadband.com/download) maybe.

A lot of the tweaking advice written by the likes of me, which obsesses over minute optimisations of efficiency, is only applicable to old ADSL connections that use ATM.
Title: Re: MTU settings (Sky fibre Max)
Post by: timeless on March 02, 2019, 12:21:36 PM
l know its pretty inaccurate, but sadly my results are pretty consistent so its not really making a whole lot of sense at the moment.
Title: Re: MTU settings (Sky fibre Max)
Post by: j0hn on March 02, 2019, 12:28:24 PM
Is that the PS4 speed test as I think its known to be pretty inaccurate?

This ^^^

I have a 1500 MTU and the PS4 speed test (the 1 within the network connection settings) shows my connection to be around 15Mb/2Mb.
It should be nearer 40Mb/7Mb.

I ignore the results as downloads from PSN Store run at the correct speed.
Title: Re: MTU settings (Sky fibre Max)
Post by: timeless on March 02, 2019, 12:45:25 PM
normally l would agree, but the fact that it handled things much better when concerning downloads at 1400 it doesnt make much sense.

in fact prior to my change l downloaded a 40gb game in around an hour since l changed to auto lm still watching 20gb come down 4 hours later which is why l dont get it.
Title: Re: MTU settings (Sky fibre Max)
Post by: Weaver on March 02, 2019, 02:48:54 PM
Assuming that the speed tests are accurate, self-relatively, which is a pretty reasonable assumption, then it seems that the mtu thing triggers some kind of weird semi-bug behaviour.
Title: Re: MTU settings (Sky fibre Max)
Post by: Chrysalis on March 03, 2019, 01:35:15 PM
are you blocking icmp packets?
Title: Re: MTU settings (Sky fibre Max)
Post by: timeless on March 03, 2019, 08:16:38 PM
not that lm aware of going through the router settings etc.