Google has hit back at claims that its search technology infringes an existing patent.

The search engine company has denied all charges in the suit, which was filed jointly by Northeastern University and a search technology company called Jarg. Google also filed a counterclaim asking the court to dismiss the patent as invalid.

The suit was filed in November in the US District Court for the Eastern District of Texas. It seeks an injunction preventing Google from further infringement, as well as royalty payments and damages.

The patent in question describes a distributed database system that breaks queries into fragments and distributes them to multiple computers in a network to get faster search results.

The plaintiffs say that Google uses this system to run its search engine, and that the system was invented by Kenneth Baclawski, an associate professor at Northeastern and one of Jarg's founders. Northeastern was awarded a patent for the system, which it has licensed exclusively to Jarg.

In its response Friday, Google argued that the patent is invalid and should not have been awarded in the first place. It cites various sections of US patent law, including those that deal with the novelty of an invention and prior art. It also cites the doctrine of "laches," which essentially requires plaintiffs to file lawsuits in a timely manner.

Its counterclaim asks the court to declare the patent invalid and unenforceable.

Both parties have requested a jury trial and legal experts have said the case could be resolved in 18 months to two years.

The patent, number 5,694,593, is dated 2 December 1997, and can be found at the US Patent & Trademark Office.