A Clearly Articulated Motivation to Combine

The Palo Alto Networks, Inc. v. Centripetal Networks, LLC case before the CAFC involves a dispute over the validity of U.S. Patent No. 10,530,903, owned by Centripetal Networks, LLC. The patent, titled “Correlating Packets in Communications Networks,” covers technology designed to identify, log, and correlate packets transmitted within a network to detect malicious activities and notify network administrators. The patent describes a system for de-obfuscating communications that may be intentionally obscured to mask the origin of malicious content.

Palo Alto Networks, Inc. (PAN) initiated an inter partes review (IPR) before the Patent Trial and Appeal Board (PTAB), asserting that claims 1-18 of the patent were invalid for obviousness.

Independent claim 1 recites:

1. A method comprising:

determining, by a computing system, that a network device has received, from a first host located in a first network, a plurality of first packets corresponding to first requests for content from a second host located in a second network, wherein the network device comprises a proxy;

determining, by the computing system, that the network device has generated a plurality of second packets corresponding to second requests, wherein the second requests correspond to the first requests, and wherein the second requests are configured to cause the second host to transmit, to the network device, the content;

generating, by the computing system, a first plurality of log entries corresponding to the plurality of first packets, wherein each of the first plurality of log entries comprises a receipt timestamp indicating a packet receipt time, and wherein the first plurality of log entries comprise first data from the first requests;

generating, by the computing system, a second plurality of log entries corresponding to a plurality of second packets, wherein each of the second plurality of log entries comprises a transmission timestamp indicating a packet transmission time, and wherein the second plurality of log entries comprise second data from the second requests;

determining, by the computing system and for each transmission timestamp, differences between at least one packet transmission time indicated by transmission timestamps and at least one packet receipt time indicated by receipt timestamps;

correlating, based on the differences and by comparing the first data and the second data, at least a portion of the plurality of first packets and at least a portion of the plurality of second packets; and

responsive to the correlating:

generating, by the computing system, an indication of the first host; and

transmitting, by the computing system, the indication of the first host.

PAN relied on three prior art references to argue that the claimed invention could have been derived by combining known technologies:

Paxton – Describes tracking network packets across network boundaries.
Sutton – Describes identifying malicious activity based on communications with darknet addresses and notifying network administrators.
Ivershen – Additional reference providing background.

When combined, PAN contended that these references disclosed all elements of the challenged claims, including the “transmitting an indication of the first host responsive to the correlation” limitation of independent claim 1. However, the Board ruled against PAN, finding that it had not provided sufficient arguments and evidence to establish by a preponderance of the evidence that independent claim 1 would have been obvious.

Specifically, the Board explained that Paxton disclosed determining a correlation with no specific action taken post-correlation and that Sutton disclosed a transmission unrelated to any correlation without the “necessary bridge,” showing that one of ordinary skill in the art would have appreciated that the transmission would be responsive to the correlation.

Federal Circuit Decision

The Federal Circuit vacated the PTAB’s decision and remanded it to the PTAB for further proceedings, requiring the Board to reevaluate and clearly articulate its findings regarding the motivation to combine and the sufficiency of the prior art in teaching the disputed claim limitations.

Motivation to Combine

The Federal Circuit reiterated that “[a]lthough identifying a motivation to combine ‘need not become a rigid mandatory formula,’ the Board must articulate a reason why a person of ordinary skill in the art would combine the prior art references .” In re Nuvasive, Inc., 842 F.3d 1376, 1382 (Fed. Cir. 1382 (Fed. Cir. 2016). Moreover, “[i]f the Board finds that there would have been no motivation to combine references…it must expressly say so with an adequate explanation.” Vicor Corp. v. SynQor, Inc. 869 F.3d 1309, 1324 (Fed. Cir. 2017).

The Federal Circuit held that the Board did not make a clear determination regarding whether a person of ordinary skill in the art would have been motivated to combine the teachings of Paxton and Sutton. Specifically, the Board never made a clear finding on whether a person of ordinary skill in the art would have been motivated to modify Paxton by adding Sutton’s step of transmitting a notification of malicious activity after Paxton’s correlation step as proposed by PAN.

Moreover, while the Board acknowledged PAN’s argument that notifying administrators of malicious activity is a logical next step to enhance network security, it failed to provide an explanation for rejecting this reasoning. Specifically, the Board failed to explain why a person of ordinary skill in the art would not have been motivated to modify Paxton to provide the recited notification as taught by Sutton in response to the correlation disclosed in Paxton.

The Federal Circuit further held that the Board failed to explain what it meant by the “necessary bridge” required to show that one of ordinary skill in the art would have appreciated that the transmission would be responsive to the correlation.

Analysis of Combined References

The Federal Circuit reiterated that an obviousness determination requires evaluating whether the combined teachings of the references would have suggested the claimed invention, rather than focusing on whether individual references disclosed each element.

The Federal Circuit held that the Board improperly analyzed the references in isolation rather than as a combined teaching. Specifically, the Federal Circuit explained the Board had failed to resolve the very issue it had identified: “whether Paxton as modified by Sutton would have taught the recited transmitting response to the correlation.”

Significance of the Ruling

The Federal Circuit’s decision reinforces the requirement for thorough and reasoned findings in IPR proceedings. Specifically, when assessing obviousness, the PTAB must:

Explicitly address whether there is a motivation to combine prior art references.
Consider the prior art in combination, rather than evaluating references individually.

This decision highlights the rigorous standard for overturning patent claims and the importance of clear, evidence-based reasoning in PTAB rulings.

Practical Implications

For patent challengers, this case underscores the need to present well-supported arguments for motivation to combine references and ensure that each claim element is addressed in the context of the combination. For patent owners, it serves as a reminder to scrutinize the logical and evidentiary basis of an IPR petitioner’s obviousness arguments.