A10 Networks Inc. , a vendor of Layer 4 through 7 equipment, filed a patent countersuit against F5 Networks Inc. (Nasdaq: FFIV) today, claiming infringement on one patent. A10 also denied the allegations in F5's patent-infringement suit, filed in April. (See A10 Files Patent Countersuit.)

Why this matters
A10 is in a legal struggle for its life. Granted, that's primarily due to a bigger lawsuit filed by Brocade Communications Systems Inc. (Nasdaq: BRCD) in August. But the F5 suit is serious as well, since A10 is a startup and doesn't have a wide portfolio of products. These cases are likely to drag on for years, but strategically it's important for A10 to keep customers' confidence up. It makes sense that A10 is counterattacking on the F5 front first, given that that suit was filed earlier and is just plain simpler. Admittedly, though, the main event will be the Brocade suit.

For more
Here's our coverage of the lawsuits, and the informal rebuttal to them that A10 CEO Lee Chen published in October.

• A10 Responds to Lawsuits
• Brocade Fires a Lawsuit at A10
• F5 Sues A10

— Craig Matsumoto, West Coast Editor, Light Reading