Does Changing MTU Settings Really Affect Download Speeds and Latency on the PS4?


MTU Settings Changes

There have been claims that changing the MTU value in the internet connections settings of your PS4 can potentially improve internet speeds and reduce lag. MTU settings can be changed on any device in reality but the PS4 has come in for special attention as the peer to peer online gaming network structure for the PS4 make it particularly susceptible to lag for online play. Understandably PS4 gamers are looking for possible ways to reduce this lag, so is there any truth to this MTU claim?

In summary, whilst there are some claims from PS4 gamers that lowering their MTU helped to reduce lag, we could not find any rigorously tested conclusive evidence that changing MTU settings improves either latency or download speeds on the PS4. More rigorous tests on the topic appear to indicate that changing MTU settings makes no difference to either download speeds or latency. Let’s look at the subject in more detail in this article.

IP-packets-MTU

MTU or Maximum Transmission Unit determines the maximum size in bytes of any packet of data that can be sent to a device over a network

What is MTU?

In networking MTU stands for Maximum Transmission Unit and dictates the maximum size for any packet of data that is sent from a device over a network.  MTU is measured in bytes and has a maximum value of 1500, so an MTU of 1500 dictates that the largest packet of data that can be sent in one go from a device over a network is 1500 bytes.

The PS4 by default sets the MTU at this maximum of 1500, with reports claiming that lowering this value to something like 1473 or 1475 can reduce latency. There were also reports that lowering the MTU value helped certain people circumvent a Playstation Network outage in December 2014, with a lower MTU allowing people to log in to the network where others couldn’t.

The idea behind this is that smaller packets of data can be sent more quickly to their destination; so smaller packets mean quicker delivery means less latency. There are videos and articles online selling a very simplified story that because lowering the MTU appeared to reduce lag for them, then it must also automatically work for everyone else. Unfortunately it is not that simple as we will go into more detail in this article.

How to Find Your Optimal MTU Setting

Quick Summary : Changing MTU value for PS4

  • Keep manually lowering the MTU value on your PS4 by manually configuring your internet connection with a lower MTU value each time.
  • Keep testing your internet connection with each progressively lower MTU value until your connection test screen displays that “packets are no longer able to be fragmented”
  • The highest MTU value just before this message was displayed is your MTU starting value.
  • Add 28 to this starting value to get your own optimum MTU value.
  • Reconfigure your PS4’s internet connection manually, entering your optimum MTU value at the correct screen.

Changing the MTU value on the PS4 appears to be an easy process but to do it correctly and thoroughly is actually more difficult and time consuming. A lot of the videos on the process just pluck the 1473 or 1475 value out of thin air as a guess, when in fact the optimum MTU value for a device has to be found individually for each device by a specific method.

We have a video below on the subject by John Glasscock on Youtube. We consistenly cite the videos of Glasscock in our articles as he is the definitive reliable Youtube source for networking tips for online gamers. He is qualified in networking and his videos test these networking theories thoroughly and rigorously to see if changing certain settings actually does improve the online experience for console gamers.

He does not throw out unverified or untested claims that certain settings will work all the time for everyone, nor does he take what could be one-off testing flukes as definitive answers to a question. He will test settings changes multiple times to make sure he has a proper data set to draw a conclusion from, so that is why he is our preferred source for answers to these questions. Here is his video on how find your optimal MTU setting for your console:

 

For the PS4, it requires a trial and error process of trying progressively lower MTU values within your connection settings until your connection test warns you that packets are not able to be fragmented. This indicates you have hit the limit for your console and network where the maximum packet size you have set is now too small to allow certain packets of data to be fully sent in one go.

A data packet that would have been sent as one before would now have to be split into two packets and sent separately because we have manually lowered our MTU below the “sweet spot”; the lowest MTU at which the packet could have been sent in one go.

So our MTU “sweet spot” is the last highest MTU value we can set it at before we get this IP packet fragmentation warning when doing our PS4 internet connection test. Glasscock reports in his videos that for him this MTU value normally hovers around 1355, but this will be different for different people depending on location and network conditions so it has to be tested individually.

Once we have this MTU “sweet spot” we also need to add 28 onto it to get our ideal MTU value to input on our PS4. The reason for this is to do with IP headers which also have to be added to a packet of data which always take up 28 bytes. Again Glasscock’s networking knowledge elevates him above other Youtube videos and resources on the subject which are not always providing accurate information on how to do these things.

So once you have your optimal MTU value – your MTU “sweet spot” value from the tests plus 28 added on – you can choose to manually set that as you MTU value on your PS4 if you wish. The process is straightforward on the PS4; you simply manually re-configure your internet connection from scratch, selecting the “Automatic” of default choice for every setting until you get to the MTU setting, which you change to “Manual” and input your optimal value into the box and save.

Do MTU Settings Affect Download Speeds or Latency?

Now we have shown how to find and input your optimal MTU value for the PS4, we will look at whether there is any evidence this actually improves network speeds or latency. Theoretically a lower MTU does have the potential to reduce network delay in a network environment, but that is no guarantee it will work in every network environment including for the PS4.

The tests that Glasscock conducts appear to show that lowering MTU settings appears to make no difference to either download speeds or latency. Whilst it does not appear to worsen them, it does not improve them either; they both remain pretty much unchanged. He also conducts multiple tests for each one to make sure any anomalies or “fluke” results do not skew his conclusions.

Lowering the MTU value makes no difference to download speeds………

 

…….and does not appear to improve latency either

Summary

So to summarise then it appears that lowering MTU settings does not appear to be beneficial in improving download speeds or reducing lag on the PS4. Both measures were tested reasonably thoroughly and stayed more or less identical between the custom “optimal” MTU value and default value of 1500 automatically assigned by the PS4. So it appears you are better off just leaving the MTU value as default or automatic on your PS4

However it is possible that for someone else, changing MTU settings may improve their latency and/or download speeds as there are so many factors that can influence network performance. It is worth trying out for more curious gamers looking to see if they can improve their online experience and the resources in this article will show them how to do it.

For the moment though we are inclined to trust the conclusions that John Glasscock comes to in his videos, as he combines networking expertise with a thorough testing method to come to the conclusion that a lower MTU setting does not impact download speeds or latency on the PS4.

For gamers looking for more effective proven ways to reduce lag for online gaming, check out the following methods which definitely have been proven to work for some people:

  • Powerline Adapters can get you onto a wired connection even at some distance from the router and are an excellent next best solution if you cannot run ethernet directly.
  • DMZ settings are an excellent way to fully open up games consoles (but not other devices) to the internet for best connectivity to other gamers online. See our article on configuring DMZ settings on your router.
  • In busy houses where there are lots of people online at the same time as gamers then Quality of Service settings can help to prioritize gaming traffic on a home network to reduce ping. See our article on the subject for a full breakdown of QoS.

See also our Gamers Section for links to accessories and some of the latest releases.

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Oliver

Online gamer and general home networking enthusiast. I like to create articles to help people solve common home networking problems.

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