Mitel Networks, a Canadian communications company, has sued Facebook for patent infringement. This comes soon after Yahoo! Inc. filed its own patent lawsuit against the social networking giant.

Mitel’s suit concerns Facebook’s infringement upon its proactive features for telephony, and an automatic web page generator. Along with the two from Mitel, and the 10 patent disputes with Yahoo!, Facebook is also dealing with a nationwide class-action lawsuit concerning user privacy.

Specifically, Mitel’s lawsuit, filed in the U.S District Court for the District of Delaware, covers these:

7,292,685, proactive features for telephony, covering systems for proactively suggesting communications features to users.

5,940,834, automatic web page generator, covering automatic Web page generation of organizational directories for use in Internet and Intranet environments.

Mitel, based in Ottawa, provides business communications and collaboration software and services.