Slow SMB performance with MacOS X clients while AFP performance is good

PROBLEM: Slow SMB performance with MacOS X clients while AFP performance is good

EXAMPLE: With MacOS X clients (OS version 10.12.6) there is a significant speed differences between AFP and SMB.
With AFP up to 780MB/s, while over SMB only up to 80 MB/s (which is roughly as much as a 1Gbit connection can take).

SOLUTION: It seems that Apple still has not fixed their "quick and dirty" fix for Badlock as described in this thread: El Capitan 10.11.5 update SMB slow (bug)

If you believe that your network is secure from man-in-the-middle attacks and the Badlock bug, then you can disable client signing.

1. Create a nsmb.conf file in /etc with vim. sudo will be required.
2. Write into the file:

[default]

     signing_required=no

Then restart your machine. Your SMB3 speeds should be comparable to AFP again.