TiVo frownTiVo is known for being more than a bit aggressive in claiming patent rights for its DVRs, and Cisco has apparently had the last straw. Scientific Atlanta's owner has sued TiVo this week in an attempt to negate four patents that TiVo is allegedly using to bully Cisco and other set-top box makers. As long as those patents are active or usable against others, TiVo will refuse to give a fair license, Cisco says -- leaving competitors with little choice but to either agree to a costly settlement or risk a ban. Before championing Cisco as the underdog, remember that it's likely counting on a large patent library as a Sword of Damocles over TiVo's head that could fall if TiVo decides on a countersuit. Regardless of the strategic maneuvering, there's no doubt that Cisco is hoping to avoid a lawsuit on the scale of the epic-length EchoStar case.