Speed performance is the important and un-negligible feature when it comes to internet communication. Port speed of a server is nothing but the rate at which speed of your server can download data from your server and upload data to your server. This speed limit is generally measured by Mbps(Megabits per second) unit.
You can verify your servers maximum uplink port speed using the below commands,
ethtool eth0 | grep -i Speed
or
ethtool eth0 | less
Also, you can check your server’s actual port connection speed using mii-tool command line utility
mii-tool
You should be privileged with your server root access in order to run the above commands through terminal.