Written by: Brendan Mee
The Court of Appeals for the Federal Circuit (CAFC) recently issued a precedential decision relating to obviousness in Palo Alto Networks, Inc. v. Centripetal Networks, LLC, 2023-1636, slip op. (Fed. Cir. December 16, 2024). The CAFC again addressed the motivation to combine references in an obviousness analysis—not only when attacking a patent as obvious, but also when arguing to uphold claims as nonobvious and therefore patentable.
The appeal arrived at the CAFC following a decision by the Patent Trial and Appeal Board (the “PTAB” or “Board”) in an inter partes review (IPR) which upheld U.S. Patent No. 10,530,903 (“the ‘903 patent”). The Board found that the Petitioner (“PAN”), following its successful institution of the IPR, had not established that the claims of the ‘903 patent were obvious.
On appeal, the CAFC remanded the case to the PTAB to articulate reasons why a combination of references did not render the claims unpatentable as obvious, and specifically to clearly address the motivation to combine that had been laid out by PAN in the IPR. The CAFC opinion did not articulate any new legal standards, but patent prosecutors may do well to note how the CAFC dissected the deficiencies in the Board’s arguments upholding the ‘903 patent claims.
Key takeaway: it is not sufficient simply to state that the claimed invention is not suggested in the references—an effective rebuttal should include an analysis of what the combined teachings of the references would have suggested to a person of ordinary skill in the art. MCM Portfolio LLC v. Hewlett-Packard Co., 812 F.3d 1284, 1294 (Fed. Cir. 2015).
The ‘903 patent, owned by Centripetal Networks LLC, is entitled “Correlating Packets In Communications Networks” and the claims are directed to identifying and correlating packets received by a network device from a host located in a first network and packets transmitted by the network device to a host located in a second network. The problem addressed by the ‘903 patent concerns network security: identifying the identity of a host outside a network boundary. The packet correlation technique is used to de-obfuscate the identity of an obfuscated host and to notify a host user and/or network administrator of a communication that is potentially with a malicious entity.
In the IPR and on appeal, the obviousness inquiry focused on claim 1 and particularly the final limitations, which the CAFC italicized:
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.
Slip op. at 3-4 (italics in the original CAFC opinion).
The CAFC summarized the proceedings below and noted that, in the IPR, PAN had relied on a first reference “Paxton” as teaching most of the limitations of claim 1, except for “transmitting an indication of the first host responsive to the correlating,” i.e., except for the italicized limitation. And for that element, PAN relied on a second reference, “Sutton”. Slip op. at 5.
And PAN provided a well developed motivation to combine Sutton with Paxton, concluding with the statement that “it would have been obvious to a [person of ordinary skill in the art] to add Sutton’s functionality . . . to Paxton’s computing system . . . to improve network security . . . .Paxton leaves, to a [person of ordinary skill in the art], remedial steps (e.g., uses of the correlation results), which are taught by Sutton.” Slip op. at 7-8 (quoting PAN’s Petition in the IPR).
Reviewing those arguments in the IPR, the Board found them insufficient to defeat the ‘903 patent claims. The Board explained that it was “left with a correlation from Paxton with no specific actions taken post-correlation, and a transmission from Sutton unrelated to any correlation, but 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.” Slip op. at 8-9 (quoting the PTAB final written decision, emphasis added).
We can pause here to appreciate that the subject matter of the ‘903 patent is a technology area in which the STEM Group at Pearl Cohen excels. Moreover, as patent prosecutors, we have not infrequently found ourselves in the exact position the Board found itself in the IPR, arguing the nonobviousness of patent claims over the combination of two patent references. Many will no doubt recognize the Board’s arguments attempting to uphold the ‘903 patent as being similar to arguments we have advanced ourselves, many times with good success, to obtain allowance. On these facts we might say: Of course Sutton’s transmitting is not responsive to the correlating—because the correlating is disclosed in Paxton!
In that light, it is useful to dissect exactly what the CAFC found deficient in the Board’s analysis.
The CAFC took issue with the Board’s lack of an express finding on the motivation to combine Paxton and Sutton. “We hold that the Board failed to make the requisite finding on motivation to combine, and that it failed to explain what it meant by ’necessary bridge.’” Slip op. at 10.
“’Our precedent dictates that the [Board] must make a finding of a motivation to combine when it is disputed.’” (quoting In re Nuvasive, Inc., 842 F.3d 1376, 1382 (Fed. Cir. 2016)). Id.
“If the Board finds that there would have been no motivation to combine [references] . . . , it must expressly say so with an adequate explanation.” (citing Vicor Corp. v. SynQor, Inc., 869 F.3d 1309, 1324 (Fed. Cir. 2017) (emphasis added). Id.
Although the CAFC says that “identifying a motivation to combine ‘need not become [a] rigid and mandatory formula[],’” it is difficult to read the opinion any other way than as requiring an express statement on the motivation to combine, including from the party rebutting obviousness.
The CAFCs declined to consider whether the Board’s “necessary bridge” language constituted an oblique reference to a motivation to combine references. But if it was, the CAFC added, “[the Board] certainly 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.” Slip op. at 11. Given [the] evidence and argument by PAN, the Board erred by not addressing the evidence and the argument for the motivation to combine and by failing to provide an adequate explanation for its finding.
The other error the Board made, according to the CAFC, was to treat the references separately in its evaluation of “whether Paxton as modified by Sutton would have taught the recited transmitting responsive to the correlation”. Slip op. at 12.
Once a motivation is found to combine references, a “bridge” between them may not be required at all, because the claim limitation at issue is considered in the context of the combination. The CAFC held, “Paxton and Sutton must be read together, not in isolation. See, e.g., Randall Mfg. v. Rea, 733 F.3d 1355, 1362 (Fed. Cir. 2013) (explaining that in KSR International Co. v. Teleflex Inc., 550 U.S. 398 (2007), the Supreme Court “[r]eject[ed] a blinkered focus on individual [prior art references]” and “required an analysis that reads the prior art in context”). Specifically, the Board must consider whether the particular combination argued by the Petitioner—modifying Paxton by adding Sutton’s notification step after Paxton’s correlation step—would meet the claim limitations at issue.” Slip op. at 13.
The “test for obviousness is not . . . that the claimed invention must be expressly suggested in any one or all of the references. Rather, the test is what the combined teachings of the references would have suggested to those of ordinary skill in the art.” MCM Portfolio LLC v. Hewlett-Packard Co., 812 F.3d 1284, 1294 (Fed. Cir. 2015) (quoting In re Keller, 642 F.2d 413, 425 (CCPA 1981)). Slip op. at 9.
One should take no pleasure in seeing the Office chastened by the CAFC on the elements of obviousness—soon enough, the shoe will be on the other foot. Going forward, one may seek to a) expressly and independently address the motivation to combine references, rather than conflating that analysis with what is disclosed in each of the references; and b) address what the combination of references teaches to the person of ordinary skill in the art.
