Filtering is a function of

switches
servers
nodes
ports

The correct answer is the first option: Switches.

Explanation:

To begin with, the term of ''switches'' is the name given to a digital device, knowing as a network switch, whose main purpose is to connects devices  on a computer network by using packet switching to receive and forward data to the destination device. The types of swithces that are for Ethernet are the most common ones nowadays. Moreover, this device mainly focuses on the linking of data between the devices connected to the switch and therefore that it is understandable that the most important characteristic is the interconnection among the equipments that are being connected together.

iphones are still better

this would start to sound a little like mortal combat