NOTE: This disposition is nonprecedential.

United States Court of Appeals 

for the Federal Circuit ______________________

BUSHNELL HAWTHORNE, LLC,

Plaintiff-Appellant

v.

CISCO SYSTEMS, INC.,

Defendant-Appellee

______________________

2019-2191

______________________

Appeal from the United States District Court for the 

Eastern District of Virginia in No. 1:18-cv-00760-TSEMSN, Judge T. S. Ellis, III.

______________________

Decided: May 14, 2020

______________________

BRIAN SHERWOOD SEAL, Butzel Long, PC, Washington, 

DC, for plaintiff-appellant. Also represented by MITCHELL 

ZAJAC, Detroit, MI. 

 ELIZABETH BRANNEN, Stris & Maher LLP, Los Angeles, 

CA, for defendant-appellee. Also represented by DOUGLAS

D. GEYSER, JOHN STOKES, PETER K. STRIS.

 ______________________

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2 BUSHNELL HAWTHORNE, LLC v. CISCO SYSTEMS, INC.

Before O’MALLEY, BRYSON, and CHEN, Circuit Judges.

O’MALLEY, Circuit Judge.

Bushnell Hawthorne, LLC (“Bushnell”) appeals a decision of the United States District Court for the Eastern District of Virginia holding all asserted claims of U.S. Patent 

No. 7,933,951 (“’951 patent”) invalid as indefinite pursuant 

to 35 U.S.C. § 112(b). Bushnell Hawthorne, LLC v. Cisco 

Sys., Inc., No. 1:18-CV-760, 2019 WL 2745735 (E.D. Va. 

July 1, 2019). For the reasons discussed below, we affirm.

I. BACKGROUND

A. The ’951 Patent

The ’951 patent, titled “Systems and Methods for Discerning and Controlling Communication Traffic,” relates 

“to identifying various types of communication traffic and 

controlling movement of that traffic within a communications network.” ’951 patent, col. 1, ll. 1–3, 18–20. The invention “permit[s] redirection of only certain types of 

communication traffic of interest[,] for example HTTP traffic, while permitting other types of communication, for example SMTP traffic, to pass without redirection.” Id. at 

Abstract. This invention is useful for redirecting internet 

traffic to generate advertising revenue. Id. 

Claim 1, the only independent claim in the ’951 patent,

is representative of the claims at issue on appeal:

1. A computer system for redirecting Internet communications, said system comprising:

a first processor that receives information 

from a computer at a point of origin;

a second processor that analyzes the information for one or more pre-defined bit 

strings or character sets;

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a third processor that receives return information from a computer that communicates with other computers on the Internet;

a fourth processor that analyzes the return 

information for said one or more pre-defined bit strings or character sets;

a fifth processor that

a) supplies one or more IP Addresses for the information requested if one or more of the predefined bit strings or character sets 

are not encountered,

b) supplies one or more second IP 

Addresses for the information requested if one or more different bit 

strings or character sets are encountered,

c) supplies one or more third IP Addresses if one or more of the pre-defined bit strings or character sets 

are encountered and a higher level 

protocol can be inferred, and/or

d) allows the traffic to flow thru unmodified; and

a sixth processor that analyzes a request 

submitted to said different IP Address for 

one or more alternative bit strings or character sets,

wherein the alternative bit strings or character sets are indicative of a particular 

higher level Internet communication protocol, and

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wherein the system further comprises maintaining a list of bit strings or character sets 

for which a different IP Address should not 

be supplied, wherein the list is updated one 

or more times after creation of the list, and 

wherein the list is updated based on monitoring of requests for: originating IP Address, requested hostname, size of a DNS 

query, frequency of a single hostname or 

domain name, port number, date, and/or 

time.

’951 patent, col. 21, ll. 9–45 (emphases added). Dependent 

claims 8, 13, and 15 contain additional limitations relevant 

to this appeal. Claim 8 requires “a seventh processor that 

receives a request to connect to a computer at said IP Address.” Id. at col. 22, ll. 7–8 (emphasis added). Claim 13 

provides “a tenth processor at the different IP Address.” Id. 

at col. 22, l. 24 (emphasis added). And claim 15 adds “items 

for the list are generated by the sixth processor that analyzes a request submitted to said different IP Address.” Id.

at col. 22, ll. 28–30 (emphasis added). 

With respect to the claim term “said different IP Address,” the specification provides: 

[T]he present invention provides a computer system for redirecting Internet communications, 

where the system comprises . . . a processor that 

analyzes a request submitted to the different IP Address for one or more alternative bit strings or character sets, wherein the alternative bit strings or 

character sets are indicative of a particular higher 

level Internet communication protocol.

Id. at col 13, ll. 3–25 (emphasis added). It also states: 

[T]he system may comprise maintaining a list of bit 

strings or character sets for which a different IP 

Address should not be supplied, for example 

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wherein items for the list are generated by the processor that analyzes a request submitted to said 

different IP Address. The list can be maintained by 

a processor that transparently passes DNS responses if one or more conditions or pre-defined bit 

strings or character sets are not encountered, and 

that supplies a different IP Address if one or more 

of the conditions or pre-defined bit strings or character sets are encountered. . . . In embodiments, a 

list is maintained on a computer that analyzes one 

or more requests submitted to the different IP Address and a list is maintained on a computer that 

analyzes the request(s) submitted to the different 

IP Address, where the two lists are compared to 

identify entries in common or not in common. 

Id. at col. 13, l. 47–col. 14, l. 1 (emphases added). Finally, 

the specification explains that:

[I]n embodiments, the system can comprise means 

for . . . returning to the submitter of the request an 

IP Address that is different from that requested. In 

embodiments, the system further comprises means 

for receiving a request for the different IP Address; 

means for analyzing the request for the different IP 

Address for pre-defined bit strings or character sets 

indicative of a particular Internet protocol . . . .

Id. at col. 17, ll. 42–57 (emphases added). 

B. District Court Proceedings

Bushnell filed suit against Cisco Systems, Inc. (“Cisco”)

in June 2018, alleging infringement of nineteen claims of

the ’951 patent. The case proceeded to claim construction. 

In its claim construction briefing, Cisco argued that all 

claims of the ’951 patent were invalid as indefinite. Specifically, Cisco argued that “said different IP Address,” and 

related terms, are indefinite. Cisco further alleged that the 

claims are indefinite because they mix statutory classes of 

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claims. Bushnell argued that all of the disputed terms 

carry their plain meaning. It contended that the plain 

meaning of the “different IP Address” terms is “an IP address supplied by the fifth processor that is different from 

the IP address for the information requested by the user or 

computer at the point of origin.” Bushnell Hawthorne, 

LLC, 2019 WL 2745735, at *2. 

Following a Markman hearing, the district court ruled 

in favor of Cisco, finding independent claim 1 indefinite on 

three separate grounds: (1) “said different IP Address” 

lacks antecedent basis and does not have a reasonably certain meaning to a person of ordinary skill in the art 

(“POSA”); (2) “a different IP Address” does not have a reasonably certain meaning to a POSA; and (3) the final limitation, providing that “the system further comprises 

maintaining a list,” improperly mixes classes of statutory 

subject matter such that it is not clear if the claim is infringed by building or using the system. Id. at *2–9. 

First, the district court explained that the antecedent 

basis for “said different IP Address” is unclear—possibly 

referring to any of three types of IP addresses that claim 1’s 

fifth processor might supply: “one or more IP Addresses,” 

“one or more second IP Addresses,” or “one or more third 

IP Addresses.” Id. at *3. Because the IP addresses mentioned in the fifth processor limitation are the first instances of the term “IP Addresses” in the claim, the district 

court presumed one of those was likely “said different IP 

Address.” Id. The fact that the fifth processor limitation 

claims three separate classes of IP addresses, however, led 

the district court to conclude that it was not possible to discern which of the three addresses was referenced by the 

disputed limitation. Id. The district court further explained that the confusion caused by the claim language is 

enhanced by the singular/plural mismatch between the 

fifth processor limitation’s potential to produce multiple IP 

addresses and the claimed singular “said different IP Address.” Id. at *4.

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Beyond the claim language, the district court found 

that the specification provides no clarification on the meaning of the term because most of the specification suffers 

from the same lack of antecedent basis problem. Id. And, 

although the specification describes a “means for returning 

to the submitter of the request an IP Address that is different from that requested,” the remainder of the specification 

is ambiguous and makes what appear to be inconsistent 

uses of the term. Id. (quoting ’951 patent, col. 17, ll. 51–

53). In some instances, the district court noted, the specification refers to a requested IP address as “the different IP 

Address.” Id. (citing, inter alia, ’951 patent, col. 13, l. 22). 

Based on this intrinsic record, the district court found that 

a POSA would be unable to discern, with reasonable certainty, whether a particular IP address was “said different 

IP Address” within the meaning of the claim. Id. at *5. It 

therefore held the claim indefinite. Id.

Second, the district court found the claim term “a different IP Address” indefinite. It explained, 

[l]ike the term “said different IP address,” the 

claim term “a different IP address” appears to allude to another IP address from which “a different 

IP address” is different. But the claim language 

and specification neither explain how or from what 

other IP address “a different IP address” differs nor 

otherwise clarify what constitutes “a different IP 

address.”

Id. at *6.

Third, the district court held claim 1 indefinite for improperly combining the structural elements of a “computer 

system” with a method element, “maintaining a list.” Id.

at *7–9. The district court further held dependent claims 

8, 13, and 15 indefinite based on the lack of clarity as to the 

meaning of the “IP Address” terms. Id. at *2–5, 6–7. 

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Having found all asserted claims indefinite, the district 

court entered judgment for Cisco. J.A. 21. Bushnell appeals. We have jurisdiction pursuant to 28 U.S.C. § 1295. 

II

“[A] patent is invalid for indefiniteness if its claims, 

read in light of the specification delineating the patent, and 

the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.” Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 

898, 901 (2014). We review a district court’s determination 

that a claim is indefinite de novo and subsidiary factual 

findings, if any, for clear error. Sonix Tech. Co. v. Publ’ns 

Int’l, Ltd., 844 F.3d 1370, 1376 (Fed. Cir. 2017). 

Bushnell argues that the district court erred in holding 

that “said different IP address,” and related terms, are indefinite. Appellant’s Br. 12–18. It contends that “said different IP Address” clearly refers to an IP address to which 

the user has been redirected. Id. at 12. Its argument is 

unavailing.

Claim 1 of the ’951 patent is, on its face, entirely unclear as to the meaning of “said different IP Address.” As 

an initial matter, “said different IP Address” appears in the 

claim without antecedent basis. Prior to that point, the 

claim recites certain IP addresses, but never a “different” 

one. See ’951 patent, claim 1. The lack of antecedent basis 

signals a potential indefiniteness problem but does not end 

the inquiry. See Energizer Holdings, Inc. v. Int’l Trade 

Comm’n, 435 F.3d 1366, 1370 (Fed. Cir. 2006) (“Whether 

[a] claim, despite lack of explicit antecedent basis . . . nonetheless has a reasonably ascertainable meaning must be 

decided in context.”). 

Moving to the broader context of the claim, however, 

only compounds the problem. Claim 1 describes three classes of IP addresses prior to the “said different IP Address” 

limitation: “one or more IP Addresses,” “one or more second 

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IP Addresses,” or “one or more third IP Addresses.” ’951 

patent, claim 1. Each of those terms is presumed to have a 

separate meaning and, therefore, presumed to refer to different classes of IP addresses. See Bd. of Regents v. BENQ 

Am. Corp., 533 F.3d 1362, 1371 (Fed. Cir. 2008). With 

three different IP addresses to choose from, a POSA faced 

with the “said different IP Address” limitation is left to 

wonder which of the different IP addresses is “said” different one. 

Further, the mismatch between the various plural IP 

addresses provided earlier in the claim and the singular 

“said different IP Address” suggests a term that is entirely 

untethered from the words around it. It is true that, as a 

general rule, a singular noun encompasses the plural for 

claim construction purposes. 01 Communique Lab., Inc. v. 

LogMeIn, Inc., 687 F.3d 1292, 1297 (Fed. Cir. 2012). This

claim construction principle, however, does not render the 

mismatch irrelevant. Where, as here, a singular/plural 

mismatch further confuses an already confused claim, it is 

proper to consider the mismatch in discerning whether a 

POSA could understand the claim with reasonable certainty. 

The specification does not clarify the meaning of “said 

different IP Address.” Much of the specification uses “the 

different IP Address” or “said different IP Address” in the 

same way as the claim—without explanation or antecedent 

basis. At one point, the specification appears to indicate, 

contrary to Bushnell’s contention, that the “different” IP 

address the patent refers to is the one which was requested. See ’951 patent, col. 13, ll. 21–22 (“a processor 

that analyzes a request submitted to the different IP Address”). At another, the specification provides comparing 

one list of requests submitted to “the different IP Address” 

to another list of requests submitted to “the different IP 

Address”—reasonably indicating that those two uses of 

“different IP Address” are not, even in the same sentence, 

referring to identical data sets. Id. at col. 13, l. 63–col.14, 

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l. 1. Given this backdrop, the single sentence in the specification that potentially supports Bushnell’s interpretation 

is insufficient to save the claim. See id. at col. 17, ll. 51–53

(“means for returning to the submitter of the request an IP 

Address that is different from that requested”).

The meaning of “said different IP Address” is entirely 

unclear on the record before us. A POSA, faced with the 

claims and the specification,1 could not, with reasonable 

certainty, discern the meaning of the claim term. See Nautilus, Inc., 572 U.S. at 901. We thus hold claim 1, and all 

claims depending therefrom, indefinite. 

III

Because we affirm the district court as to the “said different IP Address” limitation and hold all asserted claims

indefinite, we do not address the remaining issues raised 

on appeal. For the reasons discussed above, we affirm the 

district court’s decision.

AFFIRMED

1 Neither party argues that the prosecution history 

sheds light on the meaning of “said different IP Address.” 

Accordingly, we do not consider it here. 

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