Ex Parte Cai

Board of Patent Appeals and Interferences

Aug 29, 2011

10784757 (B.P.A.I. Aug. 29, 2011)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte XIANGRONG CAI
____________

Appeal 2009-010515
Application 10/784,757
Technology Center 2100
____________

Before JOSEPH L. DIXON, HOWARD B. BLANKENSHIP, and
JAY P. LUCAS, Administrative Patent Judges.

BLANKENSHIP, Administrative Patent Judge.

DECISION ON APPEAL

STATEMENT OF THE CASE
This is an appeal under 35 U.S.C. § 134(a) from the Examiner’s final
rejection of claims 1-16, which are all the claims in the application. We
have jurisdiction under 35 U.S.C. § 6(b).
We reverse.
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Representative Claim
1. A method of maintaining consistent group
membership data at a Designated Router executing the Protocol
Independent Multicast (PIM) protocol including the steps of:

receiving, at the Designated Router, an IGMP
membership message from an IGMP host operating according
to the Internet Group Multicast Protocol (IGMP) protocol;

translating the IGMP membership message into a PIM
membership message; and

selectively forwarding the PIM membership message to a
device upstream from the Designated Router, including
delaying forwarding a PIM prune message in response to an
IGMP Leave if the Designated Router is in the upstream path
from the IGMP host.

Examiner’s Rejections
Claim 10 stands rejected under 35 U.S.C. § 112, second paragraph, as
being indefinite.
Claims 1-16 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over Watkinson (US 7,233,987 B2) and Haggerty (US
6,331,983 B1).

ANALYSIS
Section 112, Second Paragraph
The legal standard for definiteness is whether a claim reasonably
apprises those of skill in the art of its scope. In re Warmerdam, 33 F.3d
1354, 1361 (Fed. Cir. 1994). The inquiry is merely to determine whether the
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claims do, in fact, set out and circumscribe a particular area with a
reasonable degree of precision and particularity. In re Moore, 439 F.2d
1232, 1235 (CCPA 1971).
Claim 10 recites, inter alia, selectively processing the PIM
membership message responsive to whether the entry is stored in the routing
table, including “not processing” a PIM prune message if a local IGMP host
exists. The Examiner contends that the negative limitation of “not
processing” renders the claim indefinite. Final Rej. 2.
We do not sustain the § 112, second paragraph rejection of claim 10.
We agree with Appellant (App. Br. 9-10) that a negative limitation in a
claim does not necessarily render the claim indefinite. The rejection offers
no reasoning in support of why the metes and bounds of “not processing” a
message in accordance with claim 10 cannot reasonably be ascertained. The
claim, on its face, merely appears to further limit the “selective” processing
of the PIM membership message by specifying one way in which
“selectively processing” the message can be effected.

Section 103(a)
The Examiner rejects claim 1 as being obvious over the combination
of Watkinson and Haggerty. The Examiner finds that Watkinson teaches all
the subject matter of claim 1, except for delaying forwarding of a PIM prune
message in response to an IGMP Leave if the Designated Router is in the
upstream path from the IGMP host. The Examiner turns to Haggerty for the
teaching deemed to be missing from Watkinson, referring to Haggerty’s text
at column 19, lines 34 through 42. Ans. 5.
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Appellant contests the Examiner’s finding with respect to Haggerty.
Appellant contends that the cited portion of the reference teaches a timer that
determines the time during which IGMP membership reports (in response to
query) must be received, rather than delaying forwarding a PIM prune
message as claimed. App. Br. 12.
The Examiner, in response, further relies on Haggerty’s text at column
19, lines 40 through 65. Ans. 9-10. Appellant responds in turn that the
rejection improperly mixes Haggerty’s statement of a problem and two
different solutions to the problem. Reply Br. 5-6.
Haggerty at column 19, line 33 through column 20, line 2 describes an
IGMP “Active Senders Problem.” A switch runs a separate IGMP state
machine on each of its access ports. The state machine sends IGMP
membership queries periodically out each port, and listens for IGMP
membership reports (“joins”) to maintain a database of local receivers per
port. If a timer expires without any reports, the switch knows there are no
receivers for that group and can stop forwarding multicast flows out that
port. Haggerty col. 19, ll. 20-31.
Haggerty teaches that, in response to the query from the switch, if a
given host reports and that host is also a sender to the group and the source
of a connection to other receivers in the domain, the membership report is
forwarded out all those receivers’ ports. Hearing this report causes other
hosts to reset their timers instead of responding to the local queries on their
links. Haggerty col. 19, ll. 33-41. The “timers” of the hosts are distinct
from the switch state machine timers, and apparently relate to avoiding
traffic congestion from all member hosts responding simultaneously. See
Haggerty col. 5, ll. 19-27.
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In any event, Haggerty further teaches that the lack of response from
other hosts may cause the problem of the switch not knowing if receivers
were still there. Haggerty teaches that a non-satisfactory solution would be
to delay queries on those access ports having active senders. Haggerty col.
19, ll. 42-47. Haggerty teaches two solutions to the problem: having the IP
protocol field distinguish IGMP packets; and “sniffing” each access port for
the duration of a “query interval” of about ten seconds. Id. at col. 19, l. 48 -
col. 20, l. 2.
In view of the foregoing teachings of Haggerty, we agree with
Appellant that the rejection has failed to establish that Haggerty teaches
delaying forwarding a PIM prune message in response to an IGMP Leave if
the Designated Router is in the upstream path from the IGMP host, as
recited in claim 1. Because each of independent claims 6 and 16 recites the
same limitation but is rejected on the same basis, we cannot sustain the
rejection of these claims and their dependent claims.
Independent claim 10 recites selectively processing the PIM
membership message responsive to whether the entry is stored in the routing
table, “including not processing a PIM prune message if a local IGMP host
exists.” The statement of the rejection does not appear to address the
foregoing limitations, but in the responsive portion of the Answer the
Examiner refers to Figure 7A of Haggerty. Ans. 10. However, we agree
with Appellant (Reply Br. 8-9) that Haggerty’s description of Figure 7A in
the text fails to relate to “not processing a PIM prune message if a local
IGMP host exists.” We thus cannot sustain the § 103(a) rejection of claim
10, nor that of the claims that depend therefrom.

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DECISION
The rejection of claim 10 under 35 U.S.C. § 112, second paragraph, as
being indefinite is reversed.
The rejection of claims 1-16 under 35 U.S.C. § 103(a) as being
unpatentable over Watkinson and Haggerty is reversed.

REVERSED

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