Wsou Investments LLC, Dba Brazos Licensing and Development v. F5, Inc., Fka F5 Networks, Inc.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
WSOU INVESTMENTS LLC, DBA BRAZOS
LICENSING AND DEVELOPMENT,
Plaintiff-Appellant
v.
F5, INC., FKA F5 NETWORKS, INC.,
Defendant-Appellee
______________________
2023-1427, 2025-1505
______________________
Appeals from the United States District Court for the
Western District of Washington in No. 2:21-cv-00126-BJR,
Senior Judge Barbara Jacobs Rothstein.
______________________
Decided: April 17, 2025
______________________
ARI B. R AFILSON, Cherry Johnson Siegmund James,
PLLC, Waco, TX, argued for plaintiff-appellant. Also rep-
resented by MARK S IEGMUND.
J ONATHAN WEINBERG, King & Spalding LLP, Washing-
ton, DC, argued for defendant-appellee. Also represented
by RYAN A. SCHMID; D AVID SHANE BRUN, Palo Alto, CA;
ANGELA CAMPBELL T ARASI, Denver, CO; BRENT P. RAY , Ar-
nold & Porter Kaye Scholer LLP, Chicago, IL.
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WSOU INVESTMENTS LLC v. F5, INC. 2
______________________
Before T ARANTO and HUGHES , Circuit Judges, and
BARNETT , Judge.1
T ARANTO, Circuit Judge.
WSOU Investments LLC, dba Brazos Licensing and
Development—hereafter Brazos—owns U.S. Patent
No. 7,548,945, which claims systems and methods for dis-
tributing certain network traffic across multiple devices.
Brazos sued F5, Inc., fka F5 Networks, Inc., alleging in-
fringement of the patent. Claim-construction proceedings
produced a claim-construction order that adopted a con-
struction of the “master device” claim limitation in accord-
ance with Brazos’s own arguments. F5 then moved for
summary judgment of noninfringement, and the district
court granted the motion, determining that no reasonable
jury could find that F5 practiced the “master device” limi-
tation as construed in the claim-construction order. WSOU
Investments, LLC v. F5 Networks, Inc., No. 2:20-cv-01878-
BJR, 2022 WL 17601874 (W.D. Wash. Dec. 13, 2022) (Sum-
mary Judgment); J.A. 51–63; J.A. 64.
Brazos appeals, challenging only the district court’s in-
terpretation of the “master device” limitation. We hold
that Brazos’s claim-construction argument on appeal is for-
feited, and we see no good reason to excuse the forfeiture.
Brazos does not contend that summary judgment was im-
proper under the district court’s construction. Accordingly,
we affirm.
1 Honorable Mark A. Barnett, Chief Judge, United
States Court of International Trade, sitting by designation.
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WSOU INVESTMENTS LLC v. F5, INC. 3
I
A
The ’945 patent is titled “System, Network Device,
Method, and Computer Program Product for Active Load
Balancing Using Clustered Nodes as Authoritative Domain
Name Servers.” The patent discusses a common situation:
An Internet user wishes to connect to an information
source (a “host”) that has a user-friendly domain name
(e.g., “www.xyz-news.com”). The user transmits the do-
main name, and a domain name service (DNS), using a
“name server,” translates the domain name into a numeri-
cal internet protocol (IP) address for a host device and
sends the IP address to the user’s own device for that device
to use to communicate directly with the identified host de-
vice. A popular host may have multiple devices (servers),
each having its own IP address, to handle the access re-
quests. In that circumstance, when a user sends a domain
name to the name server, the name server communicates
with the host’s “authoritative name server (ANS),” which
selects a particular one among the host’s devices and sends
the IP address for that device to the user’s device to enable
it to communicate directly with the selected host device.
’945 patent, col. 1, line 28, through col. 2, line 2.
The patent concerns the ANS’s selection among avail-
able host devices. The patent notes that one “known tech-
nique” is “DNS round-robin,” which involves cycling
through a “predefined, static list of the IP addresses of the
multiple devices” of the host as queries are received. Id.,
col. 2, lines 11–15. But that technique, the patent says, has
“several shortcomings”: For instance, the ANS may select
an unavailable host device, causing a connection error for
the user, or a certain host device may become overloaded if
users happen to remain connected to it for a longer period.
Id., col. 2, lines 28–52.
The ’945 patent proposes what it describes as an im-
provement by providing “a means by which a cluster of
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WSOU INVESTMENTS LLC v. F5, INC. 4
devices shares a domain name and functions as the author-
itative name server for the domain.” Id., col. 2, lines 60–
64. Each “device or node” in the cluster “repeatedly an-
nounce[s] status information, such as [its] existence on the
network, current load percentage, number of active connec-
tions, and IP address.” Id., col. 2, line 64, through col. 3,
line 3; see also id., col. 3, lines 22–24. “One of the network
devices may be designated as a master device, wherein the
master device is assigned an IP address as the authorita-
tive domain name server.” Id., col. 3, lines 20–22. The
master device may be capable of receiving a user request,
selecting a device to communicate with the client “based on
the status information,” and returning the IP address of
that device to the client. Id., col. 3, lines 24–30. And, the
specification states, “[t]he designation of master device
may be transferred as necessary from one device to another
device.” Id., col. 7, lines 37–38.
Representative claims 1, 6, and 12 state as follows,
with the phrase in dispute here highlighted:
1. A system comprising:
a plurality of network devices grouped in a cluster,
wherein each network device has a different re-
spective device internet protocol (IP) address;
wherein one of the network devices is designated
as a master device;
wherein the master device is assigned an IP ad-
dress corresponding to an IP address of an author-
itative domain name server; wherein each network
device is configured to communicate status infor-
mation to at least the master device in the clus-
ter;
wherein the master device is configured to receive
a domain name service (DNS) query based upon a
client request, select one of the network devices to
communicate with the client based on the status
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WSOU INVESTMENTS LLC v. F5, INC. 5
information of each of the network devices, and re-
turn a device IP address of the selected one of the
network devices in response to the DNS query.
. . .
6. An apparatus comprising:
a processor configured to receive status infor-
mation from each of a plurality of network devices
grouped in a cluster; the processor further config-
ured to receive a domain name service (DNS) query
based upon a client request; select one network de-
vice from among the cluster of the network devices
including the network device itself to communicate
with a client based on the status information of
each of the network devices, and return a device in-
ternet protocol (IP) address of the selected one of
the network devices in response to the DNS query,
wherein the network device is designated as a
master device and is assigned an IP address cor-
responding to an IP address of an authoritative do-
main name server.
. . .
12. A method comprising:
designating one network device, among a plurality
of network devices grouped in a cluster, as a mas-
ter device, wherein the master device is assigned
an internet protocol (IP) address corresponding to
an IP address of an authoritative domain name
server;
communicating status information from each net-
work device to at least the master device in the
cluster;
receiving a domain name service (DNS) query
based upon a client request;
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WSOU INVESTMENTS LLC v. F5, INC. 6
selecting one of the network devices to communi-
cate with the client, based on the status infor-
mation of each of the network devices; and
returning a device IP address of the selected one of
the network devices in response to the DNS query.
Id., col. 8, line 63, through col. 10, line 15 (emphases
added).
B
In January 2021, Brazos sued F5 in the district court
for the Western District of Washington, alleging infringe-
ment of the ’945 patent. J.A. 95–100. F5 filed an answer
in February 2021, denying the infringement allegations
and asserting affirmative defenses and counterclaims (in-
cluding of invalidity).
In the following months, the parties prepared for a
claim-construction hearing set for December 2021. J.A.
18719–20 (Dkt. 36); J.A. 9782–970. In its opening claim-
construction brief, Brazos argued that no express construc-
tion of “a master device” was necessary and that a relevant
artisan would understand its ordinary meaning to be “a de-
vice in a cluster that is configured to select other device(s)
at a given time.” J.A. 370. Brazos contended that “the pa-
tent does not require ‘a single network device,’ as F5 pro-
poses,” because “the patent contemplates that any device
can serve as the master.” J.A. 371 (second emphasis
added); see also id. (quoting ’945 patent, col. 4, lines 52–53)
(“Any node in the cluster is generally capable of functioning
as the master node.”). In contrast, F5 proposed: “[a] single
network device controlling the other devices in the same
cluster.” J.A. 18653. F5 argued that “the claim language
and specification reflect that only one device at a time is
the master.” J.A. 18653. In the responsive brief, Brazos
reiterated that “a master device” was not limited to “a sin-
gle network device” because “[t]he patent contemplates
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WSOU INVESTMENTS LLC v. F5, INC. 7
that a ‘master device’ can be any device and can change.”
J.A. 834.
On January 28, 2022, after the hearing, the district
court issued a claim-construction order. WSOU Invest-
ments, LLC v. F5 Networks, Inc., No. 2:20-cv-01878-BJR,
2022 WL 268825 (W.D. Wash. Jan. 28, 2022) (Claim Con-
struction); J.A. 1–18. It discussed the disputed issues
about the meaning of the “master device” phrase, including
the issue relevant now on appeal: “whether [a master de-
vice] should be defined as a ‘single device’ or simply ‘a de-
vice.’” Id. at *7. The district court “agree[d] with [Brazos’s]
definition,” stating: “While [F5] is correct that the patented
technology contemplates there being only one master de-
vice in a cluster at a given time, any device in the cluster
can serve as the master device, and the device playing the
master role may change as needed.” Id. (emphasis added).
The court thus adopted Brazos’s “a device” construction
precisely to avoid the inflexibility of F5’s “a single device”
construction. The court observed that “[t]his flexibility and
interchangeability is among the patented technology’s in-
tended improvements upon the prior art, in which only one
device, separate from the others in the cluster, served as
the ANS.” Id. The district court wrote that F5’s “proposed
use of ‘a single network device’ seems more aptly to de-
scribe the prior art than the patented technology.” Id.
In June 2022, after the parties had completed the cru-
cial discovery, F5 moved for summary judgment of nonin-
fringement and invalidity. J.A. 7665–701. F5 contended
that, under the district court’s claim-construction order,
“the ’945 patent requires . . . that any cluster device can be
designated as the master device,” yet there was no evidence
that any more than one device in F5’s product could be des-
ignated as a master device. J.A. 7676–79 (capitalization
omitted); see also J.A. 13420–27. Brazos argued in opposi-
tion that “neither the Court’s construction nor the patent
require[s] . . . each device in the cluster to be interchange-
able, even though the claims do permit other devices in the
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WSOU INVESTMENTS LLC v. F5, INC. 8
cluster to be designated as master at a given time.” J.A.
9011 (emphases added).
On December 13, 2022, the district court granted F5’s
motion for summary judgment. See generally Summary
Judgment. It first noted that “[t]he parties’ primary dis-
pute on summary judgment concerns whether the [’]945 pa-
tent necessarily requires that any device in a cluster of
devices can serve as the master device at any given time,
and thus that a product can only infringe the patent if it
possesses this capability.” Id. at *3. Referring “to this ca-
pability as ‘interchangeability,’” id. at *3 n.3, the district
court then summarized the parties’ positions: F5 was argu-
ing that “interchangeability is a necessary component,”
while Brazos was arguing that interchangeability was
“‘permissible’ but not required.” Id. at *3. The district
court concluded that Brazos’s interpretation “defies the
plain language of the [claim-construction] order,” under
which “[F5’s] product cannot infringe the patent unless it
features a system in which any device in a cluster can func-
tion as the master device at any given time.” Id. at *3–4
(emphasis added). The district court then held that there
was no genuine factual dispute as to noninfringement, so
F5 was entitled to summary judgment. Id. at *4–6. With-
out addressing F5’s invalidity counterclaims, the court dis-
missed the “matter” with prejudice. J.A. 64.
Brazos timely appealed. Upon this court’s sua sponte
order inquiring into the existence of a final judgment, the
parties jointly moved the district court to dismiss F5’s
counterclaims without prejudice. ECF Nos. 64, 66. We dis-
missed the appeal and issued the mandate to the district
court. ECF Nos. 67–68. The district court dismissed the
counterclaims without prejudice on March 3, 2025, after
which Brazos filed a new notice of appeal and this court
recalled the mandate and proceeded to oral argument on
the already-filed briefs. ECF Nos. 69–70. We now have
jurisdiction under 28 U.S.C. § 1295(a)(1).
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WSOU INVESTMENTS LLC v. F5, INC. 9
II
“We review a district court’s grant of summary judg-
ment under the standard applied in the regional circuit”—
here, the Ninth Circuit. Genuine Enabling Technology
LLC v. Nintendo Co., 29 F.4th 1365, 1372 (Fed. Cir. 2022).
The Ninth Circuit reviews a grant of summary judgment
without deference. Id.; see, e.g., Terpin v. AT & T Mobility
LLC, 118 F.4th 1102, 1110 (9th Cir. 2024). We review a
district court’s claim construction without deference and
any underlying factual determinations for clear error. Gen-
uine, 29 F.4th at 1372. Forfeiture (often called “waiver”) of
claim-construction positions is a matter of Federal Circuit
law, not regional-circuit law. See Lazare Kaplan Interna-
tional, Inc. v. Photoscribe Technologies, Inc., 628 F.3d 1359,
1376 (Fed. Cir. 2010); Harris Corp. v. Ericsson Inc., 417
F.3d 1241, 1250–51 (Fed. Cir. 2005). “To support a sum-
mary judgment of noninfringement it must be shown that,
on the correct claim construction, no reasonable jury could
have found infringement on the undisputed facts or when
all reasonable factual inferences are drawn in favor of the
patentee.” Netword, LLC v. Centraal Corp., 242 F.3d 1347,
1353 (Fed. Cir. 2001).
Brazos’s appeal depends on its argument that the dis-
trict court erred in its claim construction. Brazos Opening
Br. at 1–2, 22–45. And Brazos’s claim-construction chal-
lenge on appeal depends on its position that, under the cor-
rect claim construction of the “master device” phrase, once
a cluster device has been selected as the master device, not
even a single one of the other cluster devices need be avail-
able to be switched in to play the master role. See id. at
39–44; Oral Arg. at 34:52–35:17, available at
https://oralarguments.cafc.uscourts.gov/default.aspx?fl=23
-1427_03052025.mp3. We cannot understand Brazos’s po-
sition on appeal any other way. It does not say that the
correct construction is that some but not all cluster devices
must be available to switch into the master role. It also
offers no argument that it could avoid summary judgment
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WSOU INVESTMENTS LLC v. F5, INC. 10
under such a construction. Nor does it say that we should
reject the district court’s construction and remand for fur-
ther proceedings to determine what the correct construc-
tion is.
The claim construction proposed by Brazos on appeal,
however, is not one that it presented to the district court.
We have long applied a very strong rule forbidding an ap-
pellant to urge a construction on appeal that asserts a dif-
ferent claim scope from what it urged in the tribunal being
reviewed. See Wash World Inc. v. Belanger Inc., 131 F.4th
1360, 1368–69 (Fed. Cir. 2025); Digital-Vending Services
International, LLC v. University of Phoenix, Inc., 672 F.3d
1270, 1273 (Fed. Cir. 2012); Conoco, Inc. v. Energy & Envi-
ronmental International, L.C., 460 F.3d 1349, 1359 (Fed.
Cir. 2006); CCS Fitness, Inc. v. Brunswick Corp., 288 F.3d
1359, 1370 (Fed. Cir. 2002); Interactive Gift Express, Inc. v.
Compuserve Inc., 256 F.3d 1323, 1347 (Fed. Cir. 2001).
Such a new position is generally forfeited. See Wash World,
131 F.4th at 1369; In re Google Technology Holdings LLC,
980 F.3d 858, 863 (Fed. Cir. 2020); Kaufman v. Microsoft
Corp., 34 F.4th 1360, 1369 (Fed. Cir. 2022).
Here, Brazos did not ask the district court to construe
the disputed claim phrase to cover a master device that is
not capable of having its master-device functions switched
over to even one other cluster device. See J.A. 348–49, 370–
73 (opening claim-construction brief); J.A. 822–24, 33–35
(responsive claim-construction brief); J.A. 9000–33 (oppo-
sition to motion for summary judgment). And this is an
especially strong case for finding forfeiture because of what
Brazos did say to the district court, not just what it failed
to say. The district court properly understood Brazos to
have argued the opposite of what it now asserts—that at
least one, indeed every, other device in the cluster must be
capable of becoming the master device. In its claim-con-
struction brief, Brazos argued that “the patent contem-
plates that any device can serve as the master.” J.A. 371
(emphasis added); see also id. (quoting ’945 patent, col. 4,
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WSOU INVESTMENTS LLC v. F5, INC. 11
lines 52–53) (“Any node in the cluster is generally capable
of functioning as the master node.”). The district court
clearly accepted that understanding of needed flexibility,
writing it into the claim-construction order as the explana-
tion for adopting the “a device” position at Brazos’s urging
in preference to the unchangeability meaning of F5’s “a sin-
gle device” position. See Claim Construction, at *7 (“The
Court agrees with [Brazos’s] definition . . . . While [F5] is
correct that the patented technology contemplates there
being only one master device in a cluster at a given time,
any device in the cluster can serve as the master device, and
the device playing the master role may change as needed.”
(emphasis added)).
After the claim-construction order, when F5 moved for
summary judgment, Brazos did not purport to ask for a
new claim construction, let alone the one it now is pressing.
Brazos discounted the district court’s express explanation
in the claim-construction order of why it chose “a device”
over “a single device” and argued that the only “actual con-
struction” was “a device.” J.A. 9011. And it argued that
“the claims do permit other devices in the cluster to be des-
ignated as master at a given time,” but that they “do not
require that each device in a cluster is capable of being des-
ignated as the master device.” J.A. 9011 (emphases added;
capitalization omitted in second quote).
We see no sound reason to excuse Brazos’s forfeiture of
its current position. The principle requiring timely and
consistent presentation of fundamental claim-construction
positions that shape the litigation is an important one for
conservation of courts’ and litigants’ resources. And Brazos
has not shown any manifest injustice or other “exceptional
circumstances.” See Wash World, 131 F.4th at 1369 (“We
may excuse forfeiture under exceptional circumstances.”);
Google, 980 F.3d at 863. Brazos affirmatively led the dis-
trict court to the position it now disowns. That position
fairly informs what “a device” means, given its contrast
with “a single device” (with its unchangeability meaning).
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WSOU INVESTMENTS LLC v. F5, INC. 12
And the specification provides support, stating: “The desig-
nation of master device may be transferred as necessary
from one device to another device.” ’945 patent, col. 7, lines
37–38. On appeal, not only has Brazos failed to challenge
the district court’s determination that noninfringement is
clear under a construction where every cluster member
could function as the master device. Brazos Opening Br.
22–45; Summary Judgment, at *4–6. It also has not con-
cretely identified how the summary judgment question
could be answered differently under a claim construction
where at least one cluster member could replace the master
device. See Oral Arg. at 33:26–35:23. We therefore will
follow the usual course and hold Brazos to its forfeiture.
III
We have considered Brazos’s remaining arguments
and find them unpersuasive. Accordingly, we affirm the
decision of the district court.
AFFIRMED
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