Microsoft Corporation v. Proxyconn, Inc.

United States Court of Appeals
for the Federal Circuit
______________________

MICROSOFT CORPORATION,
Appellant

v.

PROXYCONN, INC.,
Cross-Appellant

v.

MICHELLE K. LEE, DIRECTOR, U.S. PATENT AND
TRADEMARK OFFICE,
Intervenor
______________________

2014-1542, -1543
______________________

Appeals from the United States Patent and Trade-
mark Office, Patent Trial and Appeal Board in No.
IPR2012-00026, IPR2013-00109.
______________________

Decided: June 16, 2015
______________________

JOHN D. VANDENBERG, Klarquist Sparkman, LLP,
Portland, OR, argued for appellant. Also represented by
STEPHEN J. JONCUS, CARLA TODENHAGEN.
2 MICROSOFT CORPORATION v. PROXYCONN, INC.

BRYAN K. WHEELOCK, Harness, Dickey & Pierce, PLC,
St. Louis, MO, argued for cross-appellant. Also represent-
ed by MATTHEW L. CUTLER.

NATHAN K. KELLY, United States Patent and Trade-
mark Office, Office of the Solicitor, Alexandria, VA, for
intervenor. Also represented by ROBERT J. MCMANUS,
SCOTT WEIDENFELLER.

______________________

Before PROST, Chief Judge, LOURIE, Circuit Judge, and
GILSTRAP, District Judge. ∗

PROST, Chief Judge.
This appeal arises from the inter partes review
(“IPR”) of U.S. Patent No. 6,757,717 (“’717 patent”) owned
by Proxyconn, Inc. (“Proxyconn”). The United States
Patent and Trademark Office, Patent Trial and Appeal
Board (“Board”) concluded that all of the challenged
claims except claim 24 were unpatentable as anticipated
under 35 U.S.C. § 102 alone or additionally as obvious
under 35 U.S.C. § 103. See Microsoft Corp. v. Proxyconn,
Inc., IPR2012-00026 and IPR2013-00109, Paper No. 73
(PTAB Feb. 19, 2014) (“Board Decision”). Microsoft
Corporation (“Microsoft”) appeals the Board’s determina-
tion that claim 24 is patentable. Proxyconn cross-appeals,
challenging the Board’s use of the broadest reasonable
interpretation standard of claim construction during
IPRs, its unpatentability determinations, and its denial of
Proxyconn’s motion to amend. Then–Deputy Director,
now Director, of the United States Patent and Trademark

∗
Honorable Rodney Gilstrap, District Judge, Unit-
ed States District Court for the Eastern District of Texas,
sitting by designation.
MICROSOFT CORPORATION v. PROXYCONN, INC. 3

Office (“Director”) intervened for the limited purpose of
addressing the Board’s use of the broadest reasonable
interpretation standard and its denial of Proxyconn’s
motion to amend. For the reasons stated below, we
affirm-in-part, reverse-in-part, and vacate-in-part and
remand for proceedings consistent with this opinion.
BACKGROUND
The ’717 patent relates to a system for increasing the
speed of data access in a packet-switched network. ’717
patent col. 1 ll. 12–15. The invention makes use of “digi-
tal digests” that act as short digital fingerprints for the
content of their corresponding documents. Id. at col. 2 ll.
9–13. By communicating the smaller digital digests in
place of the documents themselves, the invention reduces
the redundant transmission of data throughout the net-
work. Id. at col. 2 ll. 17–25.
The ’717 patent discloses several embodiments. The
most basic embodiment is depicted in Figure 4, shown
below.

In this embodiment, the receiver/computer (46) sends a
request for data to the sender/computer (42). The send-
er/computer calculates a digital digest on the data stored
in its memory and transmits the digest to the receiv-
er/computer. The receiver/computer then searches its
4 MICROSOFT CORPORATION v. PROXYCONN, INC.

own memory for data with the same digest. If it finds
such data, it uses that data as if it were received from the
sender/computer and issues a positive indication signal to
the sender/computer, completing the transaction. If the
receiver/computer does not find such data, it sends a
negative indication to the sender/computer, prompting the
sender/computer to transmit the actual data to the receiv-
er/computer. Id. at col. 7 ll. 18–36, 51–67.
In another embodiment, depicted in Figure 11 shown
below, the network additionally interposes intermediar-
ies, such as a gateway computer and a caching computer,
between the sender/computer and receiver/computer.

In this embodiment, the gateway (60) intercepts a digital
digest sent from the sender/computer (42) to the receiv-
er/computer (46), saves it in its memory, and passes it
unchanged to the receiver/computer. If the gateway then
intercepts a negative signal from the receiver/computer,
the caching computer (62) searches for data with the same
digital digest in its network cache memory. If that digest
is found, the gateway sends the data to the receiv-
er/computer, changes the indication signal to positive, and
then passes the indication signal on to the send-
er/computer. Id. at col. 8 l. 57–col. 9 l. 24.
MICROSOFT CORPORATION v. PROXYCONN, INC. 5

The ’717 patent concludes with 34 claims directed to
systems and methods for increasing data access in a
packet-switched network.
Microsoft filed two separate IPR petitions on the ’717
patent, each challenging different claims. The Board
joined the two proceedings and granted review of certain
of Microsoft’s challenges to the patentability of claims 1,
3, 6, 7, 9–12, 14, and 22–24. During the proceedings,
Proxyconn filed a motion to amend, seeking to substitute
(among others) new claims 35 and 36 for claims 1 and 3,
respectively. In its final written decision, the Board
determined that claims 1, 3, 6, 7, 9–12, 14, 22, and 23
were unpatentable under § 102, that claims 1, 3, and 10
were additionally unpatentable under § 103, but that
claim 24 had not been shown to be unpatentable. The
Board also denied Proxyconn’s motion to amend, conclud-
ing, inter alia, that Proxyconn did not meet its burden of
establishing that it was entitled to the amended claims,
and rejecting Proxyconn’s argument that it did not need
to establish patentability over a reference that was not
part of the original bases of unpatentability for which
review of claims 1 and 3 was instituted.
Both parties appealed from the Board’s decision, and
the Director intervened. We have jurisdiction under 28
U.S.C. § 1295(a)(4)(A).
DISCUSSION
As a general matter, we review the Board’s conclu-
sions of law de novo and its findings of fact for substantial
evidence. See In re Gartside, 203 F.3d 1305, 1316 (Fed.
Cir. 2000). In Teva Pharmaceuticals U.S.A., Inc. v.
Sandoz, Inc., 135 S. Ct. 831 (2015), the Supreme Court
clarified the standards of review for claim construction.
Pursuant to Teva’s framework and our review of Board
determinations, we review the Board’s ultimate claim
constructions de novo and its underlying factual determi-
6 MICROSOFT CORPORATION v. PROXYCONN, INC.

nations involving extrinsic evidence for substantial evi-
dence. See Teva, 135 S. Ct. at 841–42.
In this case, because the intrinsic record fully deter-
mines the proper construction, we review the Board’s
claim constructions de novo. Teva, 135 S. Ct. at 840–42.
To the extent the Board considered extrinsic evidence
when construing the claims, we need not consider the
Board’s findings on that evidence because the intrinsic
record is clear. See Phillips v. AWH Corp., 415 F.3d 1303,
1318 (Fed. Cir. 2005) (en banc).
I
Proxyconn’s threshold challenge to the Board’s actions
is that the broadest reasonable interpretation standard of
claim construction should not apply during IPRs. Proxy-
conn argues that the U.S. Patent and Trademark Office
(“PTO”) exceeded its authority in promulgating 37 C.F.R.
§ 42.100(b), and that the broadest reasonable interpreta-
tion is inappropriate during IPRs in light of the patentee’s
limited ability to amend its claims.
Proxyconn’s argument is foreclosed by our decision in
In re Cuozzo Speed Techs., LLC, 778 F.3d 1271 (Fed. Cir.
2015), rendered after the briefing in this case began. In
Cuozzo, this court held that the broadest reasonable
interpretation standard in IPRs “was properly adopted by
PTO regulation.” Id. at 1282. Because we are bound by
the decision in Cuozzo, we must therefore reject Proxy-
conn’s argument that the Board legally erred in using the
broadest reasonable interpretation standard during IPRs.
That is not to say, however, that the Board may con-
strue claims during IPR so broadly that its constructions
are unreasonable under general claim construction prin-
ciples. As we have explained in other contexts, “[t]he
protocol of giving claims their broadest reasonable inter-
pretation . . . does not include giving claims a legally
incorrect interpretation.” In re Skvorecz, 580 F.3d 1262,
MICROSOFT CORPORATION v. PROXYCONN, INC. 7

1267 (Fed. Cir. 2009); see also In re Suitco Surface, Inc.,
603 F.3d 1255, 1260 (Fed. Cir. 2010) (“The broadest-
construction rubric coupled with the term ‘comprising’
does not give the PTO an unfettered license to interpret
claims to embrace anything remotely related to the
claimed invention.”). Rather, “claims should always be
read in light of the specification and teachings in the
underlying patent.” Suitco, 603 F.3d at 1260. The PTO
should also consult the patent’s prosecution history in
proceedings in which the patent has been brought back to
the agency for a second review. See Tempo Lighting Inc.
v. Tivoli LLC, 742 F.3d 973, 977 (Fed. Cir. 2014). Even
under the broadest reasonable interpretation, the Board’s
construction “cannot be divorced from the specification
and the record evidence,” In re NTP, Inc., 654 F.3d 1279,
1288 (Fed. Cir. 2011), and “must be consistent with the
one that those skilled in the art would reach,” In re Cor-
tright, 165 F.3d 1353, 1358 (Fed. Cir. 1999). A construc-
tion that is “unreasonably broad” and which does not
“reasonably reflect the plain language and disclosure” will
not pass muster. Suitco, 603 F.3d at 1260.
With these principles in mind, we now turn to the
three claim constructions challenged by the parties in this
appeal.
II
A
Proxyconn challenges the Board’s construction of the
phrase “gateway . . . connected to said packet-switched
network in such a way that network packets sent between
at least two other computers” recited in claim 6, and
incorporated into dependent claims 7 and 9. Representa-
tive claim 6 reads:
6. A system for data access in a packet-switched
network, comprising:
8 MICROSOFT CORPORATION v. PROXYCONN, INC.

a gateway including an operating unit, a memory
and a processor connected to said packet-switched
network in such a way that network packets sent
between at least two other computers pass through
it;
a caching computer connected to said gateway
through a fast local network, wherein said caching
computer includes an operating unit, a first
memory, a permanent storage memory and a pro-
cessor;
said caching computer further including a net-
work cache memory in its permanent storage
memory, means for a digital digest and means for
comparison between a digital digest on data in its
network cache memory and a digital digest re-
ceived from said packet-switched network through
said gateway.
’717 patent col. 10 l. 64–col. 11 l. 12 (emphases added).
Before the Board, Proxyconn contended that the term
“two other computers” referred only to the send-
er/computer and the receiver/computer. Microsoft con-
tended that there was no limitation on the phrase “two
other computers,” and that those two other computers
could be any two computers connected on the network to
the gateway, including the caching computer. The Board
agreed with Microsoft, concluding that the “two other
computers” were not limited just to the sender/computer
and the receiver/computer. The Board then concluded
that claims 6, 7, and 9 were anticipated by the “DRP”
reference.
The Board erred in concluding that the “two other
computers” could include the caching computer. Begin-
ning with the language of the claims, claim 6 recites a
system comprising a gateway, a caching computer, and
“two other computers.” ’717 patent col. 10 l. 54–col. 11 l.
MICROSOFT CORPORATION v. PROXYCONN, INC. 9

12. Not only are the “two other computers” recited inde-
pendently from, and in addition to, the gateway and
caching computers, the word “other” denotes a further
level of distinction between those two computers and the
specific gateway and caching computers recited separately
in the claim.
The specification confirms that the phrase “two other
computers” is limited to the sender/receiver and comput-
er/receiver. Other than in claim 6 itself, the phrase “two
other computers” is used three times in the specification,
each time as part of the embodiment containing the
gateway and caching computer intermediaries. Id. at col.
2 ll. 43–57, col. 3 ll. 12–26, col. 8 l. 57–col. 9 l. 9. And in
each instance where it is used, the phrase “two other
computers” describes components that are separate and
distinct from the gateway and the caching computer. Id.
For example, the specification states: “Gateway 60 is
connected to a wide-area packet-switched network in such
a way that network packets sent between at least two
other computers 42 and 46 pass through the gateway 60.
The caching computer 62 uses a part of its permanent
storage memory for network cache memory 66.” Id. at col.
8 l. 64–col. 9 l. 1 (emphases added). As shown in refer-
enced Figure 11, the “two other computers 42 and 46” in
this passage are the sender/computer and receiv-
er/computer, respectively. Read together with labeled
Figure 11, this portion of the specification makes clear
that the gateway, the caching computer, and the “two
other computers” are each separate and distinct compo-
nents of the overall system. The Board’s construction,
which expands the “two other computers 42 and 46” to
include the separately identified caching computer, is
unreasonably broad in light of the language of the claims
and specification.
Because the Board’s determination that claims 6, 7,
and 9 were unpatentable was based on an unreasonably
10 MICROSOFT CORPORATION v. PROXYCONN, INC.

broad construction of the term “gateway . . . between at
least two other computers,” we vacate the Board’s find-
ings of unpatentability of claims 6, 7, and 9 and remand
for proceedings consistent with this opinion.
B
Along similar lines, Proxyconn also challenges the
Board’s construction of the terms “sender/computer” and
“receiver/computer” in independent claims 1, 10, and 22,
and incorporated into dependent claims 3 and 23. Repre-
sentative claim 1 reads:
1. A system for data access in a packet-switched
network, comprising:
a sender/computer including an operating unit, a
first memory, a permanent storage memory and a
processor and a remote receiver/computer includ-
ing an operating unit, a first memory, a perma-
nent storage memory and a processor, said
sender/computer and said receiver/computer
communicating through said network;
said sender/computer further including means for
creating digital digests on data;
said receiver/computer further including a net-
work cache memory and means for creating digi-
tal digests on data in said network cache memory;
and
said receiver/computer including means for com-
parison between digital digests.
’717 patent col. 10 ll. 31–45 (emphases added).
The Board construed “sender/computer” to mean a
computer that sends data and “receiver/computer” to
mean a computer that receives data, and further deter-
mined that both terms were broad enough to encompass
intermediaries. The Board then concluded that claims 1,
MICROSOFT CORPORATION v. PROXYCONN, INC. 11

3, 10, 22, and 23 were anticipated by the “Santos” refer-
ence and that claims 1, 3, and 10 were additionally ren-
dered obvious by the “Yohe” and “Perlman” references.
Proxyconn argues on appeal, as it did before the Board,
that the terms “sender/computer” and “receiver/computer”
should be limited to just those two computers; they should
not be construed as encompassing the separate interme-
diary gateway and caching computers. Microsoft disa-
grees, arguing that the ’717 patent does not limit either
term to a single machine or a single function.
The Board erred in concluding that the terms “send-
er/computer” and “receiver/computer” were broad enough
to include the intermediary gateway and caching comput-
ers for similar reasons as explained above. The language
of the specification consistently refers to the send-
er/computer, receiver/computer, gateway, and caching
computers as separate and independent components of an
overall system. The figures of the ’717 patent separately
identify and number each component of the system. And
nowhere does the ’717 patent indicate that the gateway
and caching computer are the same as, or can be sub-
sumed within, the sender/computer and receiv-
er/computer.
It is true, as Microsoft and the Board point out, that
Figure 4 describes a system wherein the receiv-
er/computer can perform its own caching, calculating, and
comparing functions. See ’717 patent col. 7 ll. 27–37. But
the mere fact that the receiver/computer can perform
those functions in the invention’s most basic embodiment
does not mean that the claim term “receiver/computer” is
the same as, or is broad enough to include, the separately
identified “gateway” and “caching computer” that are
associated only with the invention’s more complicated
Figure 11 embodiment. To the contrary, each time the
terms “gateway” and “caching computer” are used in the
’717 patent, they are differentiated from the “send-
er/computer” and “receiver/computer.”
12 MICROSOFT CORPORATION v. PROXYCONN, INC.

The Board’s reliance on the specification’s statement
that the gateway may be “integrally formed with the
caching computer,” id. at col. 9 ll. 6–8, is misplaced. The
cited sentence merely explains that the gateway and the
caching computer can be integrated together; it says
nothing about integration of those intermediaries with
the sender/computer and receiver/computer. Nor was the
Board correct in basing its constructions on an observa-
tion that the described computers may or may not be
located in separate housings. The patent does not use the
word housing at all, much less give any indication that
the proper construction of “sender/computer” and “receiv-
er/computer” depends on the physical location of the
claimed computers. Stated simply, the Board’s construc-
tion of “sender/computer” and “receiver/computer” to
include the intermediary gateway and caching computers
does not reasonably reflect the language and disclosure of
the ’717 patent.
Because the Board’s determination that claims 1, 3,
10, 22, and 23 were unpatentable was based on an unrea-
sonably broad construction of the terms “send-
er/computer” and “receiver/computer,” we vacate the
Board’s findings of unpatentability of claims 1, 3, 10, 22,
and 23 and remand for proceedings consistent with this
opinion.
C
For its part, Microsoft challenges the Board’s con-
struction of the phrase “searching for data with the same
digital digest in said network cache memory” in inde-
pendent claim 22, and incorporated in dependent claim
24. Claim 22 reads:
22. A method for increased data access performed
by a receiver/computer in a packet-switched net-
work, said receiver/computer including an operat-
ing unit, a first memory, a permanent storage
MICROSOFT CORPORATION v. PROXYCONN, INC. 13

memory, a processor and a network cache
memory, said method comprising the steps of:
receiving a message containing a digital digest
from said network;
searching for data with the same digital digest in
said network cache memory,
if data having the same digital digest as the digi-
tal digest received is not uncovered, forming a
negative indication signal and transmitting it
back through said network; and
creating a digital digest for data received from
said network cache memory.
’717 patent col. 12 ll. 30–45 (emphasis added). Claim 24
adds an additional requirement that is not at issue in this
appeal.
Before the Board, Microsoft contended that the ’717
patent equates “search” with “check for,” and that the
searching step of claim 22 means comparing only two
individual digest values against one another to determine
whether they match. Proxyconn contended that the
searching step instead means identifying, from among a
set of data objects, a data object with the matching digital
digest. The Board agreed with Proxyconn, concluding
that the searching step required the ability to identify a
particular data object with the same digital digest from a
set of potentially many data objects stored in the network
cache memory. The Board then concluded that claim 24,
which depends from claim 22, was not rendered invalid by
the Yohe and/or Perlman references.
The Board correctly construed the phrase “searching
for data with the same digital digest in said network
cache memory.” Although the word “searching” is not
defined in the ’717 patent, it is used several times
throughout the specification. For example, the ’717
14 MICROSOFT CORPORATION v. PROXYCONN, INC.

patent states that the receiver/computer “searches its
network cache memory 48 for data with the same digest.”
’717 patent col. 7 ll. 56–57. This sentence makes clear
that the action of “searching” is performed on the entire
network cache memory, not just on a single data object.
The patent further explains that the action of “searching”
can be performed on multiple, different memory storages:
the “receiver/computer 46 may search not only in its
network cache memory 48, but also in predefined loca-
tions in its permanent storage memory.” Id. at col. 8 ll.
50–53. Not only does the specification use the term
“searching” to mean checking amongst a set of data ob-
jects, it also uses the term “searching” in a way that is
distinct from the term “comparing,” the latter of which is
used to describe the action of checking one digital digest
against another: “The receiver/computer also has compar-
ison means 54 for comparing between such a calculated
digital digest and a digital digest received from the net-
work.” Id. at col. 7 ll. 34–37. Microsoft’s proposed con-
struction, which would essentially equate “searching”
with “comparing,” would render the additional “compar-
ing” language in the specification meaningless.
On appeal, Microsoft argues that Figure 5, which uses
the term “check for,” supports its construction. Even if
Microsoft is correct that Figure 5’s “check for” language
corresponds to the “searching” step, Microsoft has not
explained why “check for” means something other than
looking among a set of data objects. Indeed, other figures
in the patent use the words “search for” and “look for” to
describe the searching step. See Figs. 8, 12, 15. Mi-
crosoft’s reliance on Figure 5 is therefore misplaced.
Microsoft additionally argues that the Board’s con-
struction is wrong because it would not make sense for
the receiver/computer to compare a digest for a target
data object (e.g., a legal brief) to digests of data objects
unrelated to that target data object (e.g., a lunch menu).
According to Microsoft, “the patent’s algorithm requires
MICROSOFT CORPORATION v. PROXYCONN, INC. 15

only a single digest-to-digest comparison operation.”
Appellant’s Br. 9, ECF No. 19. But this argument suffers
from the same flaw described above: “comparing” is not
the same as “searching.” Microsoft acknowledges this
point in its brief, stating: “the ‘search’ for a matching data
object ends with a comparison between a single pair of
digests.’” Id. at 10. While it may true that the searching
process ends with the comparison between the two target
data objects, neither the claims nor specification limit the
“searching” step to that final comparison. Based on the
clear language of the specification, the Board was correct
in concluding that the broadest reasonable interpretation
of “searching for data with the same digital digest in said
network cache memory” includes searching in a set of
potentially many data objects. 1
On appeal, Microsoft’s only argument for reversing
the Board’s determination on claim 24 is that the Board’s
construction of claim 22’s “searching” limitation was
wrong. Because we agree with the Board’s construction,
and because Microsoft does not alternatively argue that
claim 24 is unpatentable even under the correct construc-
tion, we affirm the Board’s determination that claim 24 is
patentable.
III
Having vacated and remanded the Board’s patentabil-
ity determinations with respect to claims 1, 3, 6, 7, 9–10,
22, and 23, and affirmed the Board’s patentability deter-
mination with respect to claim 24, the only patentability
determinations left for us to address are those relating to
claims 11, 12, and 14.

1 We would reach the same result if we were to ap-
ply the traditional claim construction framework set forth
in Phillips, 415 F.3d 1303.
16 MICROSOFT CORPORATION v. PROXYCONN, INC.

The Board concluded that claims 11, 12, and 14 were
anticipated by the DRP reference. DRP describes a
protocol for the efficient replication of data over the
internet. DRP explains that the inefficiency of download-
ing the same data more than once can be avoided through
the use of “content identifiers” uniquely associated with
individual pieces of data. The content identifiers are
compiled into an index, which serves as a snapshot of the
state of a set of files at any given time, and which is
retrieved by a client using a normal “GET” request. After
a client’s initial data download, a client can update con-
tent by downloading a new version of the index and
comparing it against the previous versions of the index.
Because each file entry in the index has a content identi-
fier, the client can determine which files have changed
and thus need to be downloaded in order to bring the
client up to date.
On appeal, Proxyconn argues that DRP does not dis-
close “receiving a response signal” recited in independent
claim 11, and incorporated into dependent claims 12 and
14. Representative claim 11 reads:
11. A method performed by a sender/computer in
a packet-switched network for increasing data ac-
cess, said sender/computer including an operating
unit, a first memory, a permanent storage
memory and a processor and said send-
er/computer being operative to transmit data to a
receiver/computer, the method comprising the
steps of:
creating and transmitting a digital digest of said
data from said sender/computer to said receiv-
er/computer;
receiving a response signal from said receiv-
er/computer at said sender/computer, said re-
sponse signal containing a positive, partial or
MICROSOFT CORPORATION v. PROXYCONN, INC. 17

negative indication signal for said digital digest,
and
if a negative indication signal is received, trans-
mitting said data from said sender/computer to
said receiver/computer.
’717 patent col. 11 ll. 34–48 (emphasis added).
In particular, Proxyconn argues that because the DRP
protocol is client-driven (e.g., because DRP’s client deter-
mines which files it needs to download to bring itself up to
date), there is no disclosure that DRP’s server “under-
stands whether the files downloaded by the client are
related to an index previously downloaded by the client,
or not.” Cross-Appellant’s Br. 55, ECF No. 22. According
to Proxyconn, “the file download by the client is not linked
to a prior index download, and therefore CANNOT be
considered a ‘response’” as required by claim 11. Id.
Proxyconn’s argument fails for the simple reason that
nothing in claim 11 requires that the sender/computer
“understand” whether a request from the receiv-
er/computer is correlated with a previous transmission.
As Microsoft points out, once the receiver/computer in the
’717 patent is unable to find a matching digital digest and
sends a negative indication to the sender/computer, “all
that’s needed from the server is to transmit the desired
file, whether or not it ‘understands’ what led the receiver
to send that negative indication.” Appellant’s Resp. and
Reply Br. 22, ECF No. 28.
We agree with the Board that the download requests
that DRP’s client sends to the server after receiving the
index from the server and comparing it to the local index
meets the “receiving a response signal” limitation of claim
11. As the Board explained, the DRP client either sends a
GET request (when none of the content identifiers are up
to date), a differential GET request (when some, but not
all, of the content identifiers are up to date), or no request
18 MICROSOFT CORPORATION v. PROXYCONN, INC.

(when all content identifiers are up to date). These three
types of requests correspond to the “response signal
containing a positive, partial, or negative indication
signal” recited in claim 11. For these reasons, we con-
clude that the Board did not err in concluding that DRP
anticipates claims 11, 12, and 14 of the ’717 patent.
IV
Finally, Proxyconn challenges the Board’s denial of its
motion to amend claims 1 and 3. 2 Before reaching the
merits of Proxyconn’s arguments, we first discuss the
legal framework governing amendments during IPRs.
A
Through enactment of the America Invents Act
(“AIA”), Congress created the new IPR proceeding for the
purpose of “providing quick and cost effective alternatives
to litigation.” H.R. Rep. No. 112-98, pt. 1, at 48 (2011),
2011 U.S.C.C.A.N. 67, 78. The AIA conveys certain
authority to the PTO to “prescribe regulations” “governing
inter partes review” and to “set[] forth standards and
procedures for allowing the patent owner to move to
amend the patent.” 35 U.S.C. § 316(a)(4), (a)(9). With
respect to amendments in particular, the statute provides
that “the patent owner may file 1 motion to amend the
patent” and that such amendment “may not enlarge the
scope of the claims of the patent or introduce new matter.”
Id. § 316(d)(1), (d)(3). The statute also provides that the
Director shall, upon final determination, “incorporate[] in
the patent . . . any new or amended claim determined to
be patentable.” Id. § 318(b).

2 Proxyconn’s motion sought to amend a number of
other claims as well. But because Proxyconn’s appeal
challenges only the Board’s denial of its motion with
respect to claims 1 and 3, we review the Board’s actions
regarding these two claims only.
MICROSOFT CORPORATION v. PROXYCONN, INC. 19

Relying on the authority granted by the AIA, the PTO
has promulgated two regulations that are relevant to this
appeal. First is 37 C.F.R. § 42.20, which applies generally
to motions practice. Section 42.20 requires that any
“[r]elief, other than a petition requesting the institution of
a trial, must be requested in the form of a motion” and
that “[t]he moving party has the burden of proof to estab-
lish that it is entitled to the requested relief.” § 42.20(a),
(c). Second is 37 C.F.R. § 42.121, which imposes specific
requirements on the amendment process. Section
42.121(a)(2) provides that: “A motion to amend may be
denied where: (i) The amendment does not respond to a
ground of unpatentability involved in the trial; or (ii) The
amendment seeks to enlarge the scope of the claims of the
patent or introduce new subject matter.”
In addition to these two regulations, a six-member
panel of the Board has also issued a decision called Idle
Free Systems, Inc. v. Bergstrom, Inc., IPR2012-00027,
2013 WL 5947697 (PTAB June 11, 2013). In Idle Free,
the panel stated that it was providing “a general discus-
sion of several important requirements for a patent
owner’s motion to amend claims.” Id. at *1. Relying on
§ 42.20(c), the Idle Free decision requires that, in motions
to amend during IPRs:
A patent owner should identify specifically the
feature or features added to each substitute claim,
as compared to the challenged claim it replaces,
and come forward with technical facts and reason-
ing about those feature(s), including construction
of new claim terms, sufficient to persuade the
Board that the proposed substitute claim is pa-
tentable over the prior art of record, and over pri-
or art not of record but known to the patent
owner. The burden is not on the petitioner to
show unpatentability, but on the patent owner to
show patentable distinction over the prior art of
record and also prior art known to the patent
20 MICROSOFT CORPORATION v. PROXYCONN, INC.

owner. Some representation should be made
about the specific technical disclosure of the clos-
est prior art known to the patent owner, and not
just a conclusory remark that no prior art known
to the patent owner renders obvious the proposed
substitute claims.
A showing of patentable distinction can rely on
declaration testimony of a technical expert about
the significance and usefulness of the feature(s)
added by the proposed substitute claim, from the
perspective of one with ordinary skill in the art,
and also on the level of ordinary skill, in terms of
ordinary creativity and the basic skill set. A mere
conclusory statement by counsel, in the motion to
amend, to the effect that one or more added fea-
tures are not described in any prior art, and would
not have been suggested or rendered obvious by
prior art, is on its face inadequate.
Id. at *4–5.
The Idle Free decision has been designated as “in-
formative.” According to the Board’s operating proce-
dures, informative decisions are “not binding authority,”
but are designated as informative in order to provide
“Board norms on recurring issues,” “guidance on issues of
first impression,” and “guidance on Board rules and
practices.” See Patent Trial and Appeal Board, Standard
Operating Procedure 2 (Revision 9), at 3 (¶ IV.A–B),
available at http://www.uspto.gov/sites/default/files/
documents/sop2-revision-9-dated-9-22-2014.pdf. The
Board has frequently cited to Idle Free when denying
motions to amend during IPRs. See, e.g., The Scotts Co. v.
Encap, LLC, IPR2013-00110, 2014 WL 2886290, at *18–
20 (PTAB June 24, 2014); Ecowater Sys. LLC v. Culligan
Int’l Co., IPR2013-0155, 2014 WL 2903758, at *18 (PTAB
June 24, 2014); Adidas AG v. Nike, Inc., IPR2013-00067,
2014 WL 1713368, at *17–18 (PTAB Apr. 28, 2014).
MICROSOFT CORPORATION v. PROXYCONN, INC. 21

B
We turn now to the events of this case. During the
IPR, Proxyconn sought to amend the ’717 patent by
replacing challenged claims 1 and 3 with substitute
claims 35 and 36, respectively. In its opposition, Mi-
crosoft argued, inter alia, that the substitute claims were
unpatentable for anticipation by DRP. DRP was not one
of the references over which the PTO originally instituted
review of claims 1 and 3. It was, however, used both as
an anticipation and an obviousness reference over which
the PTO instituted review of claims 6, 7, 9, 11, 12, and 14.
In its reply, Proxyconn argued that because DRP was not
one of the references over which the PTO had instituted
review of claims 1 and 3, the Board exceeded its authority
under § 42.121(a)(2)(i) to deny substitute claims 35 and 36
for failure to “respond to a ground of unpatentability
involved in the trial.” Proxyconn did not otherwise argue
that substitute claims 35 and 36 were patentable over
DRP.
In its final written decision, the Board denied Proxy-
conn’s motion to amend claims 1 and 3 for two reasons. 3
First, citing § 42.20(c) and Idle Free, the Board held that
Proxyconn failed to meet its burden of establishing pa-
tentability of the substitute claims. In particular, the
Board stated:
Proxyconn has not proffered sufficient arguments
or evidence to establish a prima facie case for the
patentability of claims 35–41. For example,

3 With respect to claim 3, the Board also denied
Proxyconn’s motion on grounds that substitute claim 36
impermissibly enlarged the scope of claim 3 in violation of
35 U.S.C. § 316(d)(3). Because we resolve this case on
other grounds, we do not review this additional basis for
the Board’s denial of Proxyconn’s motion.
22 MICROSOFT CORPORATION v. PROXYCONN, INC.

Proxyconn has not: (i) construed the newly added
claim terms; (ii) addressed the manner in which
the claims are patentable generally over the art;
(iii) identified the closest prior art known to it; (iv)
addressed the level of ordinary skill in the art at
the time of the invention; or (v) discussed how
such a skilled artisan would have viewed the new-
ly recited elements in claims 35–41 in light of
what was known in the art. Instead, Proxyconn
attempts to distinguish claims 35–41 only from
the prior art for which we instituted review of cor-
responding claims 1, 3, 6, 10. 11. 22, and 23. Mot.
Amend 4–15. Consequently, Proxyconn has failed
to establish a prima facie case for the patentabil-
ity of claims 35–41.
Board Decision at 55.
Second, the Board rejected Proxyconn’s argument that
§ 42.121(2)(a)(i) precluded the Board from relying on the
DRP reference. Again citing § 42.20(c), the Board stated
that “Proxyconn carries the burden of proof with respect
to the patentability of its proposed claims” and that
“Microsoft [was] entitled” to rely on DRP. Id. at 56.
Because “Proxyconn provide[d] no evidence to counter
Microsoft’s contentions that DRP anticipate[d] [claims 35
and 36],” the Board denied Proxyconn’s motion. Id.
On appeal, Proxyconn argues that § 42.121(a)(2) pro-
vides a complete list of the bases for which the Board can
deny a motion to amend. According to Proxyconn, the
Board exceeded its own regulation by imposing the addi-
tional requirements of Idle Free and by relying on the
DRP reference. The Director defends the Board’s actions,
arguing that § 42.121(a)(2) is not exhaustive. According
to the Director, a patentee seeking to amend its claims
during IPRs must meet both the “procedural require-
ments” of § 42.121(a)(2) as well as the “substantive bur-
den” imposed by § 42.20(c), as it has been interpreted
MICROSOFT CORPORATION v. PROXYCONN, INC. 23

through adjudicative Board decisions like Idle Free.
Intervenor’s Resp. Letter 2, ECF No. 50.
This appeal, therefore, presents the question of wheth-
er the Board permissibly relied on the requirements of
Idle Free and the DRP reference in denying Proxyconn’s
motion to amend. We review Board decisions using the
standards set forth in the Administrative Procedure Act, 5
U.S.C. § 706. In re Sullivan, 362 F.3d 1324, 1326 (Fed.
Cir. 2004). “Under that statute, we set aside actions of
the Board that are arbitrary, capricious, an abuse of
discretion, or otherwise not in accordance with law, and
set aside factual findings that are unsupported by sub-
stantial evidence.” Id. “We accept the Board’s interpreta-
tion of Patent and Trademark Office regulations unless
that interpretation is ‘plainly erroneous or inconsistent
with the regulation.’” Id. (quoting Eli Lilly Co. v. Bd. of
Regents of the Univ. of Wash., 334 F.3d 1264, 1266 (Fed.
Cir. 2003)); see also Auer v. Robbins, 519 U.S. 452, 461–62
(1997); In re Garner, 508 F.3d 1376, 1378 (Fed. Cir. 2007).
C
At the threshold, we agree with the Director that
§ 42.121(a)(2) is not an exhaustive list of grounds upon
which the Board can deny a motion to amend. In the AIA,
Congress gave the PTO authority to “prescribe regula-
tions” “governing inter partes review” and to “set[] forth
standards and procedures for allowing the patent owner
to move to amend the patent.” § 316(a)(4), (a)(9). Con-
gress also provided that, upon final decision, the Director
should incorporate only those amended claims that are
“determined to be patentable.” § 318(b). Given these
directives, the PTO promulgated both the general regula-
tion setting forth the patentee’s burden to establish it is
entitled to its requested relief, § 42.20, as well as the more
specific regulation setting forth particular requirements
regarding the amendment process, § 42.121. Both regula-
tions are plainly applicable to motions to amend filed
24 MICROSOFT CORPORATION v. PROXYCONN, INC.

during IPRs, and Proxyconn does not argue that the PTO
acted outside its statutory authority in promulgating
either one.
What Proxyconn does challenge is the Board’s inter-
pretation of those regulations as permitting it to deny
Proxyconn’s motion to amend claims 1 and 3 for failure to
establish patentability over DRP—a reference that the
Board did not rely on when instituting review of those
particular claims. The Director responds that its authori-
ty to do so comes from § 42.20(c), as it has been interpret-
ed in Idle Free—namely, as requiring the patentee “to
show patentable distinction [of the substitute claims] over
the prior art of record.” Idle Free, 2013 WL 5947697, at
*4. According to the Director, it is permissible for the
PTO to use adjudicative Board decisions like Idle Free,
rather than traditional notice and comment rule-making,
to set forth all the conditions that a patentee must meet
in order to satisfy its burden of amendment under
§ 42.20(c).
Some question the wisdom of the PTO’s approach.
Since IPRs were created, they have rapidly become a
popular vehicle for challenging the validity of issued
patents. See Patent Trial and Appeal Board
AIA Progress, available at http://www.uspto.gov/sites/
default/files/documents/aia_statistics_05-14-2015.pdf
(reporting 2,894 IPR petitions received as of May 14,
2015). Patentees who wish to make use of the statutorily
provided amendment process deserve certainty and
clarity in the requirements that they are expected to
meet. A fluid, case-based interpretation by the PTO of its
own regulations risks leaving interested members of the
public in a state of uncertainty, without ascertainable
standards and adequate notice to comply.
Despite such concerns, we recognize that “the choice
between rulemaking and adjudication lies in the first
instance within the [agency’s] discretion.” NLRB v. Bell
MICROSOFT CORPORATION v. PROXYCONN, INC. 25

Aerospace Co. Div. of Textron, 416 U.S. 267, 294 (1974).
The Director argues that adjudication is appropriate here
because the PTO “has not ‘had sufficient experience with
[motions to amend] to warrant rigidifying its tentative
judgment into a hard and fast rule’” and that the PTO
“thus ‘must retain power to deal with [such motions] on a
case-by-case basis if the administrative process is to be
effective.’” Intervenor’s Resp. Letter 3, ECF No. 50 (al-
terations in original) (quoting SEC v. Chenery Corp., 332
U.S. 194, 202–03 (1947)). Because there is merit to these
arguments, we cannot say that the PTO has abused its
discretion in choosing adjudication over rulemaking.
Nor can we say that the Board’s interpretation of
§ 42.20(c) in Idle Free—requiring the patentee to “show
patentable distinction [of the substitute claims] over the
prior art of record,” Idle Free, 2013 WL 5947697, at *4—is
plainly erroneous or inconsistent with the regulation or
governing statutes. 4 The legal framework provides that a
patentee must “move to amend the patent,” § 316(a)(9),

4 Importantly, this case does not call on us to decide
whether every requirement announced by the Board in
Idle Free constitutes a permissible interpretation of the
PTO’s regulations. The Idle Free decision is not itself
before us, and we resolve this case only with respect to
the Board’s having faulted Proxyconn for “attempt[ing] to
distinguish claims [35 and 36] only from the prior art for
which we instituted review of corresponding claims [1 and
3]” and, ultimately, for “fail[ing] to establish by a prepon-
derance of evidence that [claims 35 and 36] are patentable
over DRP.” Board Decision at 55–56. We do not address
the other requirements of Idle Free that the Board relied
upon. Nor do we address, for example, Idle Free’s re-
quirement that the patentee to show patentable distinc-
tion over all “prior art known to the patent owner.” Idle
Free, 2013 WL 5947697, at *4.
26 MICROSOFT CORPORATION v. PROXYCONN, INC.

that the Director should incorporate only those amended
claims that are “determined to be patentable,” § 318(b),
and that the patentee has the burden to “establish that it
is entitled to the requested relief,” § 42.20(c).
The Board has reasonably interpreted these provi-
sions as requiring the patentee to show that its substitute
claims are patentable over the prior art of record, at least
in the circumstances in this case. First, nothing in the
statute or regulations precludes the Board from rejecting
a substitute claim on the basis of prior art that is of
record, but was not cited against the original claim in the
institution decision. Second, the very nature of IPRs
makes the Board’s interpretation appropriate. During
IPRs, once the PTO grants a patentee’s motion to amend,
the substituted claims are not subject to further examina-
tion. Moreover, the petitioner may choose not to chal-
lenge the patentability of substitute claims if, for
example, the amendments narrowed the claims such that
the petitioner no longer faces a risk of infringement. If
the patentee were not required to establish patentability
of substitute claims over the prior art of record, an
amended patent could issue despite the PTO having
before it prior art that undermines patentability. Such a
result would defeat Congress’s purpose in creating IPR as
part of “a more efficient and streamlined patent system
that will improve patent quality and limit unnecessary
and counterproductive litigation costs.” H.R. Rep. No.
112-98, pt. 1, at 40 (2011), 2011 U.S.C.C.A.N. 67, 69.
Proxyconn argues that the Board’s actions are in con-
flict with § 42.121(a)(2)(i). But Proxyconn confuses re-
quirements governing permissible reasons for seeking
amendment versus those governing what must ultimately
be shown of amended claims. Section 42.121(a)(2)(i)
simply requires that a patentee’s amendment be made in
order to “respond to a ground of unpatentability involved
in the trial,” and not for some other reason. As the PTO
explained, this rule is meant to “enhance efficiency of
MICROSOFT CORPORATION v. PROXYCONN, INC. 27

review proceedings . . . . [A]ny amendment that does not
respond to a ground of unpatentability most likely would
cause delay, increase the complexity of the review, and
place additional burdens on the petitioner and the Board.”
Changes to Implement Inter Partes Review Proceedings,
Post-Grant Review Proceedings, and Transitional Pro-
gram for Covered Business Method Patents, 77 Fed. Reg.
48,680, 48,705 (Aug. 14, 2012). Assuming an amendment
is appropriately responsive to the grounds of unpatenta-
bility involved in the trial, the patentee must still go on to
show that it is entitled to its substitute claim. The PTO
explained this as well, stating that a motion to amend
“will be entered so long as it complies with the timing and
procedural requirements” but “even if entered, will not
result automatically in entry of the proposed amendment
into the patent.” Id. at 48,690. Requiring the patentee to
establish that its substitute claims are patentable over
the prior art of record does not run afoul of
§ 42.121(a)(2)(i).
Proxyconn also argues that the Board’s interpretation
and reliance on DRP was “fundamentally unfair” because
Proxyconn was unable to defend substitute claims 35 and
36 against that reference. Cross-Appellant’s Resp. Letter
2, ECF No. 51. We reject that argument. Although DRP
was not one of the original references for which review of
claims 1 and 3 was instituted, it was very much a part of
the entire proceedings. In particular, it was relied on by
the Board for instituting review of six closely related
claims. And after Microsoft filed an opposition brief
arguing that substitute claims 35 and 36 were invalid
over DRP, Proxyconn had the opportunity to distinguish
those claims from DRP in its reply brief but simply chose
not to do so. Lastly, at the oral hearing, the Board ex-
plained to Proxyconn that Proxyconn was required to
demonstrate the patentability of substitute claims 35 and
36 over the DRP reference. This is not a case in which the
patentee was taken by surprise by the Board’s reliance on
28 MICROSOFT CORPORATION v. PROXYCONN, INC.

an entirely new reference or was not given adequate
notice and opportunity to present arguments distinguish-
ing that reference. Rather, this is a case where the prior
art relied on by the Board was front and center through-
out the course of the proceedings.
For all of these reasons, we conclude that the Board
acted permissibly in requiring Proxyconn to establish the
patentability of substitute claims 35 and 36 over the DRP
reference. And based on Proxyconn’s failure to do so, we
affirm the Board’s denial of Proxyconn’s motion to amend
claims 1 and 3.
V
For the foregoing reasons, we reverse the Board’s con-
structions of the term “gateway . . . between at least two
other computers” in claims 6, 7, and 9 and the terms
“sender/computer” and “receiver/computer” in claims 1, 3,
10, 22, and 23, and therefore vacate and remand its
unpatentability determinations of those claims. We
affirm the Board’s construction of the “searching” limita-
tion in claim 22, the Board’s determination that claim 24
is patentable, and the Board’s conclusion that DRP antic-
ipates claims 11, 12, and 14. We also affirm the Board’s
denial of Proxyconn’s motion to amend claims 1 and 3.
AFFIRM-IN-PART, REVERSE-IN-PART, VACATE-
IN-PART, AND REMAND
COSTS
Each party shall bear its own costs.