D-Link DFL-M510 Faq page 16

What is the limitation to detect and block Skype?
Q:
A:
With DFL-M510-Pattern-3.16, there are two known constraints for blocking Skype:
1. A network administrator sets DF-M510 to block Skype after an internal user has
logged into Skype network, and the user never logs off.
2: A user first logs in to Skype network with his/her computer at one place, does not log off,
and then connects his/her computer to the network managed by DFL-M510.
Note: by definition, the behaviour below is called quit Skype network, which is different
from the behaviour of log off Skype.
D-Link Nordic Technical Support 16