SSH Communications Security Corporation v Sony Mobile Communications AB & Ors

For anticipation, a prior-art document must provide a clear and unmistakable disclosure of the claimed subject matter, or clear instructions to do or make something that would infringe. Disclosure is assessed by construing the document through the eyes of the skilled person, with expert evidence assisting on technical language. Here, the combination of the NAT Minutes and NAT Guidelines clearly disclosed maintaining a NAT mapping for UDP communications by sending periodic keepalive packets before timeout. The references to keepalives concerned packets refreshing the NAT timer, not HTTP application-layer Keep-Alive tokens. A feature absent from the disclosure may nevertheless be obvious where the skilled person would take it as an evident practical step. The appeal was dismissed.

SSH, proprietor of European Patent EP (UK) 2,254,311, appealed from the decision of the Patents Court ([2016] EWHC 2359 (Ch)). The deputy judge held that claims 1 and 2 lacked novelty, and that claims 1 and 3 were obvious, over publications known as the NAT Minutes and NAT Guidelines. He rejected an obviousness attack based on common general knowledge and found that the patent, if valid, would have been infringed.

Following a worldwide confidential settlement, Sony took no part in the appeal. SSH pursued the appeal solely to overturn the finding of invalidity. The central questions were whether the Minutes and Guidelines clearly disclosed the subject matter of claims 1 and 3 and, alternatively, whether any difference from the disclosure was obvious.

1. Appeal dismissed. Although the appeal had become unopposed after settlement, the court heard it on its merits because it would not be right to restore a patent held invalid below without deciding whether that decision was wrong. The approach in Halliburton Energy Services Inc v Smith International (North Sea) Ltd and ors [2006] EWCA Civ 185 was followed.
2. Prior art must first be construed through the eyes of the notional skilled person, with expert evidence assisting where necessary on technical language. For anticipation, the prior art must disclose subject matter which, if performed, would necessarily infringe, or must contain a clear description or clear instructions to do or make something that would infringe.
3. The Guidelines addressed the problems caused by NATs and instructed designers what to do and avoid. Section 3.5 explained that UDP sessions were tracked by timeouts. The Minutes repeated that point and, in the question-and-answer exchange, identified keepalives as a solution to maintaining the mapping. Read together, the documents clearly and unmistakably disclosed sending periodic packets sufficiently frequently to prevent or at least ameliorate timeout and preserve the NAT mapping. This anticipated claim 1.
4. The keepalives disclosed were unrelated to HTTP Keep-Alive tokens. Those tokens operated at the application layer over HTTP and TCP, while the NAT was unaware of them and they did not refresh the UDP mapping. The court rejected the argument that the HTTP feature was necessarily part of the common general knowledge merely because HTTP 1.1 was a standards-track protocol.
5. Even if the disclosure had not been clear, the deputy judge was entitled to find it obvious to send keepalives frequently enough to prevent timeout, applying the structured approach to obviousness in Pozzoli SpA v BDMO SA [2007] EWCA Civ 588. Claim 3 added equal headers for the keepalive and ordinary datagrams. That feature was not disclosed, but was obvious because the packets had to pass through the NAT and be translated in the same way for the mapping to be refreshed.
6. The deputy judge’s findings were therefore correct and the appeal was dismissed.

• Court of Appeal (Civil Division): Appeal dismissed.
• Patents Court: The deputy judge held claims 1 and 2 anticipated, claims 1 and 3 obvious over the NAT Minutes and Guidelines, and the patent infringed if valid: [2016] EWHC 2359 (Ch).