Client MTU setting and TCP

Frank, HB9FXQ

David-N5PSM

I don't understand your two questions yet......    However, I suspect you are asking if the MTU setting is to "Throttle back" the UDP traffic in order to give better usability in poor internet conditions.  I can understand this regardless weather we are talking about V2.5 or V3   Where is the second question?  Please straighten me out.

Mike-VA3MW

You would only change the MTU values if you feel that your packets are being fragmented or broken up.  It is not a throttle feature.  In fact setting it too low is better than setting it too high (within reason).

For most of us on Cable modems or DSL modems, you should not have to touch the setting.  Do not change it without doing some testing.

If you think your MTU value is wrong there, you can do some tests using Windows command prompt to test it.  

https://kb.netgear.com/19863/Ping-Test-to-determine-Optimal-MTU-Size-on-Router


As an example, I know a value of 1500 works at home, but as I sit here at a Tim Horton's in Canada (eh?) I can see it should be set to 1492 as I did the above test.

Mike va3mw

Frank, HB9FXQ

Roland HB9VQQ

To me it seems like the flex implementation is lacking PMTU functionality

Roland HB9VQQ

Frank, HB9FXQ

Peter K1PGV

I remember a discussion long ago, and the conclusion was that the radio does not support Path MTU Discovery. That stuck me, at the time, as less than a great choice, but given my personal needs (LAN only) I didn’t pursue the issue further.

Peter
K1PGV

Frank, HB9FXQ

No statement from FRS? 

Mike-VA3MW

What is your question?

Frank, HB9FXQ

Question is, if path MTU discovery will be implemented in the radio firmware / radio network stack

Mike-VA3MW

Hi Frank

We have a policy of not commenting on future features until they are released.  So, at this time, I guess the answer is no comment.  

73, Mike

Paul - KB5MU

This exact problem now arises in what's becoming a plain-vanilla, consumer internet configuration. In the case I'm investigating, it's Verizon 5G Home Internet. This is a fast, cheap, uncapped data service that's widely available and very simple to install. Entirely suitable as a consumer replacement for wired home internet service. And it DOES NOT WORK with Smartlink because of the inability of the Flexradio to adapt to slightly reduced MTU limits.

I was able to get it working with the Windows SmartSDR using the workaround in W0QL's blog post updated January 2022: https://w0qlremotebase.wordpress.com/2020/03/30/flexradio-6600-on-order/ . Without a day to **** and some familiarity with how TCP works, this would have been impossible. And it's still not a solution for Maestro users, among others.

This really needs to be fixed in the Flexradio network stack ASAP.

73 -Paul KB5MU