As the name suggests the actual packet processing is performed
by multiple instances of the Click Modular Router [42].
Click allows to build complex VNFs using simple and reusable
components, called elements. Click includes over 300 elements
supporting functions such as packet classification, access control,
deep packet inspection. Elements can be composed in order to realize complex VNFs. Finally, Click can be easily extended
with custom processing elements making it possible to support
features that are not provided by the standard elements.