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Whats the true mtu here?

Jonesc93
Hooked
Posts: 5
Registered: ‎17-04-2021

Whats the true mtu here?

Okay so coming over from sky I always used 1500 and everything was fine. Moved to plusnet and since then had really bad problems gaming on ps5. After abit of digging I came across the mtu value being 1492 for pppoe. However on the plusnet router the max mtu through CMD is 1460 so the router is set at 1488. Now I have my own openreach modem and an xr500 with duma OS when that is set up over pppoe I get 1492 mtu as being the max. And then a quick cmd test shows that my max is 1492. Again however when gaming with this set up using 1492 it feels horrible I feel like I'm a day behind bullet hit detection is appalling and every time I die I'm dead before I'm even notified. I drop my mtu down to 1488 and the problems seem to go away or at least to the point where I can presume most other problems are from the game servers and everything else involved when it comes to servers and lag compensations.

All I want to know is why my line or router links at 1488 is the line mtu 1488 or is mtu created in the home through the router I.e my xr500 setting it to 1492 should work optimally when intact it doesn't?.

Is there anyone that fully understands the line management and what the mtu max really is and why the plusnet router is set to 1488 there has to be a reason for shipping them and giving them to people to use with that mtu value.

Any help much appreciated
Thank you
9 REPLIES 9
idonno
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Registered: ‎22-10-2015

Re: Whats the true mtu here?

I've been down this path. I presume you've done something similar but using your gaming portal instead.

 

FWIW Mine is 1488 (I'm not on a PN router or service) and seems ok

Ever helpful. Grin Sure, I’d love to help you out. Now which way did you come in?
Jonesc93
Hooked
Posts: 5
Registered: ‎17-04-2021

Re: Whats the true mtu here?

Using my gaming portal instead?
corringham
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Registered: ‎25-09-2015

Re: Whats the true mtu here?

There's a lot of information about MTU and MSS (maximum Segment Size) available on the web - some of it is almost intelligible to a layperson. Here's a simple and incomplete overview...

Basically, MTU is the maximum packet size that can be sent over TCP. Each packet is made up of a header section and a data section. The MSS is basically the maximum size of the data section - and that is really just the MTU minus the header size.

Each protocol has a different header size, and individual applications may also add header information.

If a packet it larger than the MTU it will be split by the sender and sent as multiple packets - this is known as fragmentation. In the vast majority cases that works just fine. The cases where it doesn't may be due to the extra delay introduced, or by an application (e.g. games) not accepting split packets (often seen as dropped packets or broken connections).

Things such as VPNs or L2TP add to the packet header size - these are not always apparent to an end user as some ISPs may route traffic using L2TP, and the only visible impact is a lower MSS. A lot of the MTU discovery tools really report MSS - which is why you add some value (28 for icmp) to the result to arrive at an MTU to use.

The MTU applies to the whole path to each destination, so you can find that testing MTU for different destinations will report different values.

In general you may find a MTU that is lower than the detected maximum is more robust, and is unlikely to degrade throughput by a noticeable amount.

Jonesc93
Hooked
Posts: 5
Registered: ‎17-04-2021

Re: Whats the true mtu here?

Yes the delay for gaming is 100% noticeable. Which is why I'm trying to work out or get an answer as to whether or not the mtu is set to 1488 on plusnets end and thus being fragmented all the time using my own router with 1492. Or that simply doesn't exist and its done on my end. The tests I have done you are right in saying lowering it may have a better result. I know there are loads of people using different mtu sizes for gaming and that is a big problem when so much data is being sent at one time and so much is received/dropped or fragmented and slowed down.

I just wondered if there was a yes or no answer to plusnets infrastructure running at 1488 or the pppoe max of 1492.

Thank you
corringham
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Registered: ‎25-09-2015

Re: Whats the true mtu here?

The point is that the MTU is path dependent - only part of that path is within the Plusnet network. There isn't a defined value that is correct for all paths.

The MTU within Plusnet's network will depend on a number of factors, including whether you have a dynamic IP or a static IP (I understand the static IPs are routed over L2TP, so will have a lower MTU).

dvorak
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Re: Whats the true mtu here?

Are you playing wired or wireless? That probably has a bigger impact that MTU on gaming.
My PS5 is wired and ports forwarded and haven’t had any issues with gaming on it.
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Jonesc93
Hooked
Posts: 5
Registered: ‎17-04-2021

Re: Whats the true mtu here?

I'm wired. I've tried alot of different stuff and I'm finding mtu to be the big difference. On sky mtu was no issue.

I've tried wired I've set up a geo filter to only connect me to the same server every time to eliminate randomness and different levels of ping to and from multiple random servers.

Nat type opened ports forwarded dmz tried it all. Mtu is definitely the difference in my tests so far.

As previously mentioned 1492 is max on my xr500 netgear router. On plusnet hub 1 it's 1488. After setting my netgear to 1488 or lower gaming is alot more consistent.

I guess as mtu isn't a massive factor when browsing or streaming I'll just find the best mtu that works for me over time.

I was just hoping there was a best/optimal for gaming so I didn't have to do this. Don't want it too low and only send x amount at a time but don't want it too high where everything is fragmented slowed down or lost
Baldrick1
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Re: Whats the true mtu here?

@Jonesc93 

If you have a gaming router then why not use that? Simply get a modem, a model 3B Huawei HG 612 works fine and can be picked up cheaply from an auction site, and scrap the Plusnet hub. 
Router settings are here. https://www.plus.net/help/broadband/broadband-connection-settings/

Jonesc93
Hooked
Posts: 5
Registered: ‎17-04-2021

Re: Whats the true mtu here?

That is exactly what I'm doing if you read my previous message. I'm just curious as to why the hub 1 uses 1488 and syncs at that mtu rate while we all know pppoe is set to 1492.

And then figure out why the increased mtu to 1492 is affecting things

Thank you