Arista Networks, Inc. v. CISCO SYSTEMS, INC., Cross-Appellant 2017-1313, 2017-1380 Appeals from the United…

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
ARISTA NETWORKS, INC.,
Appellant
v.
CISCO SYSTEMS, INC.,
Cross-Appellant
______________________
2017-1313, 2017-1380
______________________
Appeals from the United States Patent and Trade-
mark Office, Patent Trial and Appeal Board in No.
IPR2015-00975.
______________________
Decided: March 28, 2018
______________________
L AUREN ANN D EGNAN , Fish & Richardson, PC, Wash-
ington, DC, argued for appellant. Also represented by
MICHAEL J. MCK EON, RALPH ADAM P HILLIPS .
J ASON M. WILCOX , Kirkland & Ellis LLP, Washington,
DC, argued for cross-appellant. Also represented by J OHN
C. O'Q UINN, CALVIN ALEXANDER SHANK; J ON WRIGHT ,
Sterne Kessler Goldstein & Fox, PLLC, Washington, DC.
______________________

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ARISTA NETWORKS, INC. v. CISCO SYSTEMS, INC. 2
Before N EWMAN, T ARANTO, and STOLL , Circuit Judges.
T ARANTO, Circuit Judge.
Arista Networks, Inc. challenged various claims of
Cisco Systems, Inc.’s U.S. Patent No. 8,051,211 in an
inter partes review. The Patent Trial and Appeal Board
of the Patent and Trademark Office determined that
Arista failed to show that certain claims are unpatentable
for obviousness. Because the Board did not adequately
explain its reasoning on a point that was central to its
analysis, we vacate the Board’s determination as to the
appealed claims and remand for further proceedings.
I
A
The ’211 patent describes and claims methods and
systems for “multi-bridge LAN aggregation.” ’211 patent,
Abstract; col. 13, lines 14–26; col. 14, lines 21–38. The
patent defines “LAN,” “host,” “frame,” and “bridge.”
“Although a LAN may refer to a computer network orga-
nized in a given locale [(i.e., a local area network)], as
used herein, the term ‘LAN’ is used to refer to a physical
connection between one or more hosts (e.g., a LAN Seg-
ment).” Id., col. 1, lines 42–45; see id., col. 1, lines 15–16.
“[T]he term ‘host’ refers to an end-station which is the
source of, or destination of, frames transmitted over a
network.” Id., col. 1, lines 45–47. “[A] frame refers to
information which is transferred between a host and a
bridge and/or between multiple bridges.” Id., col. 1, lines
22–23. And “[b]ridges are intermediate network devices
which can be used to interconnect LANs at the link layer
to enable computers on one LAN to communicate with the
computers of another LAN.” Id., col. 1, lines 30–33.
The patent states that the invention combines two
ideas. One is “[l]ink aggregation (also known as trunk-
ing),” which groups LANs together and treats the group
“as a single link with the capacity of all the links com-

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ARISTA NETWORKS, INC. v. CISCO SYSTEMS, INC. 3
bined.” Id., col. 2, lines 28–32. The other is redundancy
of a host’s connections to a separate computer network, by
use of multiple intermediate network devices such as
bridges, routers, or switches. Id., col. 1, lines 29–33, 48–
50, 62 through col. 2, line 1; see id., col. 4, lines 22–25.
One aspect of the claimed invention is “tunneling.”
The patent says: “As used herein, tunneling is used to
refer to transmitting a frame without examination.” Id.,
col. 5, lines 59–61. It contrasts tunneling with what it
says is the way that bridges generally move frames:
“when a bridge receives a frame, it generally examines
the frame to determine the corresponding LAN Segment
to forward the frame to.” Id., col. 5, lines 61–63. Describ-
ing Figure 3B, the patent continues: “However, in accord-
ance with the present invention, bridge 342 is configured
to internally transmit a frame between bridge inter-
connect port 366 and port A0 directly, without such
examination. Thus, port A0 on bridge [342] is slaved
through sub-port A99.0 to sub-port B99.0 of bridge 344.
Bridge 342 is essentially transparent to bridge 344 and
host 356.” Id., col. 5, line 65 through col. 6, line 4.
B
On April 1, 2015, Arista petitioned for an inter partes
review of claims 1, 2, 6–9, 12, 13, and 17–20 of the ’211
patent. On October 6, 2015, the Board, acting for the
Director of the Office, instituted a review of independent
claims 1 and 12, for anticipation by U.S. Patent No.
6,910,149 (Perloff), and of dependent claims 2, 6–9, 13,
and 17–20, for obviousness over the combination of Perloff
and U.S. Patent No. 6,931,529 (Kunzinger). Arista Net-
works, Inc., v. Cisco Sys. Inc., IPR2015-00975, 2015 WL
5895790, at *7 (P.T.A.B. Oct. 6, 2015). All of the depend-
ent claims contain a limitation that requires “tunneling.”
Perloff discloses “multi-device link aggregation,”
which provides increased bandwidth and redundancy by

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ARISTA NETWORKS, INC. v. CISCO SYSTEMS, INC. 4
linking multiple network devices together. Perloff, col. 1,
lines 7–14, 55–60; col. 5, lines 9–17. Kunzinger discloses
a method to establish “tunnels” using the IP Security
Protocol (IPSec) to protect “datagrams (i.e. packets)
traveling through the network.” Kunzinger, col. 1, lines
8–12; col. 2, lines 30–32, 53–59; col. 3, lines 7–18. Accord-
ing to Kunzinger, “[t]unneled packets in IPSec have an
outer IP header . . . and an inner IP header.” Id. col. 3,
lines 7–14. “When IPSec is used in ‘tunnel’ mode, the
complete inner packet, which is comprised of both the
inner header and the payload, is protected as the packet
travels through the tunnel. However, the outer header
remains in clear text form as the packet travels through
the tunnel.” Id. Arista, in its petition, relied on
Kunzinger to disclose the tunneling limitation common to
all of the dependent claims on appeal. J.A. 96–101, 109–
10.
In its October 5, 2016 Final Written Decision, the
Board determined that claims 1 and 12 were anticipated
by Perloff. Arista Networks, Inc., v. Cisco Sys. Inc.,
IPR2015-00975, Paper No. 36, at 17 (P.T.A.B. Oct. 5,
2016) (Final Written Decision). Cisco has not cross-
appealed the anticipation finding.1 As to claims 2, 6–9,
13, and 17–20, the Board determined that Arista had
failed to show unpatentability. It concluded that Arista
did not prove a premise of its obviousness challenge to
those claims, namely, that the tunneling limitation is
disclosed in Kunzinger. Id. at 25.
1 Cisco has, however, cross-appealed the Final
Written Decision, but it has done so only to preserve a
constitutional challenge to the inter partes review regime,
recognizing that our precedent forecloses the challenge
but that the issue is pending before the Supreme Court in
Oil States Energy Servs., LLC v. Greene’s Energy Grp.,
LLC, No. 16-712, cert. granted, 137 S. Ct. 2239 (2017).

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ARISTA NETWORKS, INC. v. CISCO SYSTEMS, INC. 5
Arista timely appeals the Board’s patentability de-
termination regarding claims 2, 6–9, 13, and 17–20. We
have jurisdiction under 28 U.S.C. § 1295(a)(4)(A).
II
We agree with Arista that the Board has not ade-
quately explained its finding that Kunzinger does not
disclose the tunneling limitation of claims 2, 6–9, 13, and
17–20 of the ’211 patent.
Claim 2 requires “tunneling said first LAN with a
third LAN through said first intermediate network de-
vice.” ’211 patent, col. 13, lines 27–30. Based on the
language of the written description quoted above, the
Board construed “tunneling” to mean “transmitting a
frame without examination, including in layer 2 and layer
3 communications.” Final Written Decision, at 10 (em-
phasis added). The Board then found that Kunzinger
does not teach that limitation because Kunzinger’s use of
the outer header for directing movement of a frame is an
“examination” excluded from “tunneling.” Id. at 24–25.
But the required analysis of Kunzinger is not that
simple, because, as the Board explained, the proper
understanding of “examination” is more complicated. The
Board recognized that “claim 11 further defines tunneling
to comprise encapsulating a frame, transmitting the
frame, de-encapsulating the frame, and directly transmit-
ting the frame.” Id. at 8 (citing ’211 patent, col. 14, lines
11–20). On that basis, the Board concluded that “encap-
sulation and de-encapsulation of a frame are not ‘exami-
nation’ of a frame, as the ’211 patent uses that term.”
Final Written Decision, at 9. In short, while “transmitting
a frame” during “tunneling” must be “without examina-
tion,” certain kinds of activities involving encapsulation
and de-encapsulation are not part of the excluded “exami-
nation”—hence may be present in what still qualifies as
“tunneling” under the ’211 patent.

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ARISTA NETWORKS, INC. v. CISCO SYSTEMS, INC. 6
Arista’s contention on appeal is that the Board im-
properly overlooked that complication of the “without
examination” portion of the “tunneling” construction when
considering Kunzinger. Most specifically, Arista focuses
on the ’211 patent’s explanation that “bridge-interconnect
port 412 encapsulates (e.g., includes a tag within, or
appended to, frame 500) and de-encapsulates (e.g., exam-
ines fields in frame 500 and/or removes tags from frame
500)” the frame. ’211 patent, col. 9, lines 14–18. The tag,
shown in Figure 5 as 506, provides information about the
destination for a frame. Id., col. 7, lines 38–42; col. 9,
lines 29–47. Arista argues that the Kunzinger-taught
examination of the outer header of an encapsulated
packet is not relevantly different from the use of fields
and tags of the encapsulated frame in the ’211 patent, the
latter not constituting an “examination” excluded from
“tunneling.” Consequently, Arista concludes, Kunzinger
teaches the “tunneling” limitation, contrary to the Board’s
finding. At the least, Arista contends, the Board did not
adequately explain why Kunzinger’s examining activities,
involving the outer header, are relevantly different from
actions permitted to be part of “tunneling” by the ’211
patent, a crucial premise of the Board’s finding that
Kunzinger does not teach that limitation.
We review the Board’s final written decisions “to en-
sure that they are not ‘arbitrary, capricious, an abuse of
discretion, . . . otherwise not in accordance with law . . .
[or] unsupported by substantial evidence.’” Pers. Web
Techs., LLC v. Apple, Inc., 848 F.3d 987, 992 (Fed. Cir.
2017) (quoting 5 U.S.C. § 706(2)(A), (E)). “[I]n order to
allow effective judicial review, . . . the agency is obligated
to provide an administrative record showing the evidence
on which the findings are based, accompanied by the
agency’s reasoning in reaching its conclusions.” Id. (quot-
ing Synopsys, Inc. v. Mentor Graphics Corp., 814 F.3d
1309, 1322 (Fed. Cir. 2016), overruled in another respect
by Aqua Prods., Inc. v. Matal, 872 F.3d 1290 (Fed. Cir.

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ARISTA NETWORKS, INC. v. CISCO SYSTEMS, INC. 7
2017), and In re Lee, 277 F.3d 1338, 1342 (Fed. Cir. 2002))
(internal quotation marks omitted). “For judicial review
to be meaningfully achieved within these strictures, the
agency tribunal must present a full and reasoned expla-
nation of its decision.” Lee, 277 F.3d at 1342.
We agree with Arista to the following extent (and we
go no further here): the Board did not adequately explain
why “transmission of the IPSec packet” in Kunzinger
includes an “examination” excluded from the “tunneling”
claimed in the ’211 patent, even while the described use of
fields and tags in the ’211 patent is not such an excluded
“examination.” Final Written Decision, at 25. The ’211
patent’s tunneling process “internally routes data . . .
depending on, for example, information associated with
the data (e.g., an encapsulation tag . . . ).” ’211 patent,
col. 7, lines 38–42. At one level of generality, in that
situation, as in Kunzinger, a portion of a frame is trans-
mitted through the tunnel without examination, while
another portion is examined to route the data to its proper
destination. That general description of what is similar
may well omit critical differences. The Board implicitly
must have so found in determining that Kunzinger shows
a forbidden “examination.” But the Board’s decision is
lacking in explanation on this key element of its analysis.
The decision “does not address, or at least does not clearly
address,” the difference between the examination of
tunneled packets in Kunzinger and the type of examina-
tion that is permissible in the tunneling process of the
’211 patent. See Pers. Web, 848 F.3d at 993.
Cisco seeks to explain the distinction in this court.
Some Board explanations can suffice even if brief, as
when the patent and the art are both clear and readily
understandable. Id. at 994. In addition, “we will uphold
a decision of less than ideal clarity if the agency’s path
may reasonably be discerned.” Bowman Transp., Inc. v.
Ark.–Best Freight Sys., Inc., 419 U.S. 281, 286 (1974); see
In re NuVasive, Inc., 842 F.3d 1376, 1382–83 (Fed. Cir.

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ARISTA NETWORKS, INC. v. CISCO SYSTEMS, INC. 8
2016). But, understood in light of our scrutiny of the
patent and the prior art, the Board’s “own explanation
must suffice for us to see that the agency has done its job
and must be capable of being ‘reasonably . . . discerned’
from a relatively concise [Board] discussion.” In re NuVa-
sive, 842 F.3d at 1383. In this case, Cisco’s attempt to
explain the distinction at issue has not sufficiently ena-
bled us to see an adequate explanation in the Board’s
opinion.
III
We vacate the Board’s decision as to the appealed
claims and remand the matter for further proceedings.
No costs.
VACATED AND REMANDED

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