What is a minimum MTU?

[Rob Townley]

I know MTU is Maximum Transmission Unit, but what is a "minimum
Maximum Transmission Unit"?
Shows up in tinc.log as "Packet for PC5 (ip.x.y.z port 655) larger
than minimum MTU, forwarding via TCP".

Ping times between tinc nodes are outrageously slow at times ...
greater than 1 second.
Othertimes, the same link will be 1ms.  For entire weekends, i could
ping from all 3 laptops out the wireless router into a switch into
another NAT to the Linux tinc server to an inside node without a
dropped packet and always under 5ms.  Then for no apparent reason, it
becomes slow - extremely slow and windows takes forever to logon and
frustrations rise.


Here is the log contents during a simple ping (when in Debug 5)
usually associated (not 100%) with very long echo times about 1 second
for what essentially is a LAN.
Receiving packet of 62 bytes (tun mode)
Sending packet of 90 bytes (tun mode)
Packet for PC5 (ip.x.y.z port 655) larger than minimum MTU, forwarding via TCP


tinc 1.13 on windows clients to tinc 1.13 on Linux server behind a NAT.

So essentially the Tablets require (at times) more than 20x the time
for an echo request to a local "LAN" node than to www.google.com.
Google is 40ms, the local node is 800ms - 5000ms.