In Storage Tech. Corp. v. Cisco Sys., Inc. (Fed. Cir. May 13, 2003), the Federal Circuit provided instructions on claim interpretation to be considered by those desiring determinations favorable to their positions, whether for infringement or noninfringement of patent rights. A patent owner accused another party of infringing various patent claims in two patents. A dispute arose about the interpretation of the following claim in the first patent.

1.  A policy caching method for use in a communication device, comprising the steps of:

determining an instance of protocol data unit (PDU) network policy from a plurality of policies to be applied to related-received PDUs based on contents of one of the related-received PDUs, wherein the related-received PDUs are a subset of a stream of PDUs and may be distributed throughout said stream of PDUs; and

caching policy identification information identifying the instance of PDU policy which is to be applied to other PDUs of the related-received PDUs.

The district court whose decision was appealed to the Federal Circuit had construed the language of claim 1 to require not only caching of policy identification information, but also caching of an instance of network policy.  The district court had based its interpretation in part on the presence of the phrase “policy caching method” or “policy cache” in the preamble of every independent claim of the patent.  The Federal Circuit determined the district court’s interpretation of claim 1 was overly narrow.

• Claim 1 does not include any step relating to caching the instance of network policy or any limitation indicating that the instance of network policy is stored in or retrieved from a cache.
• The limitation “caching policy identification information” requires only the identification information, not the instance of network policy, to be cached.
• The terms “policy caching method” or “policy cache” in the preamble of each claim serve as a convenient label for the invention as a whole and do not limit claim scope.
• The written description consistently uses the terms “policy caching method” and “policy cache” to refer to the invention as a whole, not to the specific step of storing an instance of network policy or to the cache that stores the instance of network policy, which the written description refers to as the “instance policy cache.”
• Only dependent claims 19, 22, and 26, which require the instance of policy to be cached, explicitly recite “instance policy cache” in the body of the claim.

In addition, the accused infringer noted that during patent prosecution the inventors had stated the instance of network policy and the policy identification information were both cached by the invention recited in claims 1, 11, and 18.  The Federal Circuit determined, with respect to the caching of the instance of network policy, the inventors’ statement could not limit the scope of claims 1, 11, or 18 because of the absence of any language in those claims referring to the caching of the instance of network policy.

Also, the Federal Circuit ruled the district court had improperly relied on extrinsic evidence in the form of a declaration by an expert presented by the accused infringer concerning the construction of claim 1.  Resort to extrinsic evidence is appropriate only when ambiguity remains after consulting the intrinsic evidence of record.  Moreover, the district court did not use the extrinsic evidence to assist in defining a claim limitation, but rather impermissibly used it to limit claim scope based on the purpose of the invention.

Another dispute arose over the construction of the claim language “protocol data unit (PDU) network policy.”  The patent owner and accused infringer had agreed the language referred to a rule or procedure set by a system administrator.  A point of contention was whether the language should be limited to filtering and auditing rules only or construed more broadly to include rules related to routing, bridging, and switching functions.

• The ordinary meaning of “network policy” as understood by one skilled in the art is a rule or procedure set by a network system administrator.
• The “Background of the Invention” section in the patent stated:
  • In a data communication network, the routing, bridging, switching, filtering, and auditing functions of protocol data units (e.g., data packets, cells, or frames which contain voice, video, or data information) are collectively handled by network policies.
  • These routing, bridging, switching, filtering, and auditing functions are also governed by policy set forth by rules and procedures set by system administrators and the like. These rules and procedures are generally known as communications network policies.
• The “Summary of the Invention” section in the patent stated:
  • Examples of such policies are filtering (e.g., forward or not forward the PDU) and/or auditing (e.g., send a copy of the PDU to a third party).
  • In addition, the instance of network policy is performed by filtering or auditing the related-received PDUs.

The Federal Circuit determined that the statements in the summary section, when read in context, do not narrow the definition provided in the background section and, therefore, the definition of “network policy” provided in the written description is a rule or procedure set by a system administrator governing one or more of a routing, bridging, switching, filtering, or auditing function.

The prosecution history, as understood in context, does not warrant a narrower claim construction.  In response to a rejection over a prior art reference disclosing a device for bridging local area networks, the inventors stated:

Unlike a bridge, which analyzes source or destination addresses to determine where data should be forwarded, the present invention more broadly analyzes the content of PDUs in order to perform filtering and auditing functions which determine if and why data should be forwarded.

Viewed in context, the inventors were distinguishing their invention from a prior art bridge that, although it performs bridging functions, lacks a mechanism for enforcing any network policies, including policies relating to filtering and auditing functions as well as policies relating to bridging functions.  The Federal Circuit therefore did not consider the inventors’ statement to be a clear and unambiguous disavowal of claim scope as required to depart from the meaning of the term provided by the written description.

The construction of the following claim in the second patent was also disputed.

14.  A protocol data unit forwarding device for use in a communication network to transfer protocol data units within the communication network, comprising:

(a) protocol data unit processor, comprising:

(i) identification means for determining media header information of a protocol data unit which is received from over the communication network;

(ii) validation means, operatively coupled to the identification means, for validating the media header information; and

(iii) modification means, operatively coupled to the identification means, for adding next operation information to the media header information based upon the determined media header information; and

(b) forwarding processor, operatively coupled to the protocol data unit preprocessor, for forwarding the protocol data unit in the communication network based upon the next operation information.

The Federal Circuit affirmed the district court’s claim construction that the “protocol data unit processor” and the “forwarding processor” must be part of the same forwarding device.  The written description emphasizes that a key benefit of the invention is that the use of the next operation information within a forwarding device reduces the processing otherwise performed by the forwarding device.  Further, the originally filed claim had contained the phrase “such that subsequent processing of the protocol data unit by the protocol data unit forwarding device is reduced,” referring back to the “forwarding device” recited in the preamble.  The inventors had deleted that phrase in a claim amendment responsive to an indefiniteness rejection from the U.S. Patent and Trademark Office (“PTO”) during the course of patent prosecution and stated in their accompanying remarks that the language was deleted as unnecessary “because the use of the added next operation information by the forwarding device is recited as part of each claim.”  Because the claim recites the use of the next operation information by the forwarding processor, it follows that the inventors considered the forwarding processor to be part of the forwarding device recited in the preamble, which therefore operates as a limitation upon the claim.  The inventors also had relied on the existence of a “forwarding device” in their remarks to the PTO during patent prosecution to distinguish their claimed invention from the prior art.

Recommendations:

In the preparation of the specification and claims of your patent application:

• Consistently use the same terminology to refer to a given concept and distinct terminology to refer to different concepts.
• When disclosing features in the specification at a level of detail which is narrower than the broadest claim, take care to tie the detailed features to an implementation of the invention rather than to the broadest claim terminology.

In the evaluation of the meaning of claim language:

• To determine whether or not language in the preamble constitutes a claim limitation, one must review the specification, the claims, and the prosecution history for the use of that language and any distinguishing language in:
  • the issued claims;
  • the originally filed claims;
  • all versions of the claims presented during patent prosecution; and
  • remarks made during patent prosecution to address matters of form as well as to distinguish prior art.
• Context for a broad meaning for a claim limitation may be provided by the disclosure in the specification, even in the background section.
• To constitute a limitation on claim coverage, a remark in the prosecution history needs to be aligned with a limitation in the patent claims.
• The meaning of remarks made during patent prosecution concerning a claim limitation may be broadened by the context provided in the specification, even in the background section.
• Only if ambiguity remains after review of the intrinsic evidence, namely, the written description and the prosecution history, should one expect extrinsic evidence to be available to assist in construction of a claim limitation.

May 16, 2003

Text Copyright © 2003 Bob Brill et al.

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