DCT

5:21-cv-00690

Correct Transmission LLC v. ADTRAN Inc

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Key Events
Amended Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 5:21-cv-00690, N.D. Ala., 03/21/2023
  • Venue Allegations: Venue is alleged to be proper in the Northern District of Alabama because Defendant ADTRAN maintains its corporate headquarters and a regular and established place of business in Huntsville, Alabama, within the district.
  • Core Dispute: Plaintiff alleges that Defendant’s telecommunications routers, switches, and access products infringe five U.S. patents related to data packet fragmentation, network loop prevention, and failure protection schemes for virtual private networks.
  • Technical Context: The technologies at issue address fundamental challenges in modern telecommunications, focusing on methods to ensure data is transmitted efficiently, reliably, and without interruption across complex, high-speed networks.
  • Key Procedural History: The complaint alleges that Defendant had pre-suit knowledge of the asserted patents via notice letters sent in 2017. For U.S. Patent No. 7,983,150, the complaint alleges that in May 2018, a related entity filed suit in Germany against ADTRAN for infringement of a corresponding European patent, resulting in a June 2019 judgment of infringement against ADTRAN's NetVanta product series.

Case Timeline

Date Event
2001-01-08 U.S. Patent No. 6,876,669 Priority Date
2001-07-27 U.S. Patent No. 7,127,523 Priority Date
2003-01-07 U.S. Patent No. 7,283,465 Priority Date
2005-04-05 U.S. Patent No. 6,876,669 Issued
2006-01-18 U.S. Patent No. 7,983,150 Priority Date
2006-07-11 U.S. Patent No. 7,768,928 Priority Date
2006-10-24 U.S. Patent No. 7,127,523 Issued
2007-10-16 U.S. Patent No. 7,283,465 Issued
2010-08-03 U.S. Patent No. 7,768,928 Issued
2011-07-19 U.S. Patent No. 7,983,150 Issued
2017-05-09 Notice Letter Sent for ’523, ’465, ’928, ’150 Patents
2017-10-02 Notice Letter Sent for ’669 Patent
2018-05-01 German Action Filed re: European Counterpart to ’150 Patent
2019-06-09 German Judgment Issued re: European Counterpart to ’150 Patent
2023-03-21 Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 6,876,669 - “PACKET FRAGMENTATION WITH NESTED INTERRUPTIONS”

  • Patent Identification: U.S. Patent No. 6,876,669, “PACKET FRAGMENTATION WITH NESTED INTERRUPTIONS,” issued April 5, 2005 (the “’669 Patent”).

The Invention Explained

  • Problem Addressed: The patent describes a problem in prior art data transmission where, once a transmitter begins sending fragments of a low-priority data packet, it cannot stop until the entire packet is sent (Compl. ¶15; ’669 Patent, col. 3:6-10). This forces higher-priority packets to wait, potentially causing unacceptable delays for services like voice, or requires the low-priority packet to be discarded entirely to ensure immediate transmission of the high-priority packet (’669 Patent, col. 3:10-13).
  • The Patented Solution: The invention proposes a multi-priority system that allows a transmitter to interrupt the transmission of a low-priority packet to service a newly arrived high-priority packet, and then resume sending the remaining fragments of the low-priority packet afterward (’669 Patent, col. 3:14-20). The system supports "nested" interruptions, where transmissions can be interrupted by packets of increasingly higher priority, without compromising the receiver's ability to reassemble all the original packets correctly (’669 Patent, col. 3:23-30). This is managed by adding an "interruption level" field to the fragment headers, indicating how many lower-priority packet transmissions have been interrupted (’669 Patent, col. 5:60-65).
  • Technical Importance: This approach aimed to improve Quality of Service (QoS) on networks carrying mixed traffic by ensuring that delay-sensitive data (like voice) could be transmitted with minimal latency without having to discard lower-priority data already in transit (Compl. ¶16).

Key Claims at a Glance

  • The complaint asserts independent claim 1 (Compl. ¶20).
  • Essential elements of claim 1 include:
    • Receiving a first datagram (low-priority) and then a second datagram (high-priority) before the first is finished.
    • In response, dividing the first datagram into fragments.
    • Transmitting the fragments of the first datagram.
    • Transmitting at least a fragment of the second datagram before transmitting the last fragment of the first datagram.
    • This transmission of the second datagram fragment comprises interrupting the transmission of the first datagram.
    • Adding a field to the interrupting fragment that indicates the number of datagrams whose transmission has been interrupted.
  • The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 7,127,523 - “SPANNING TREE PROTOCOL TRAFFIC IN A TRANSPARENT LAN”

  • Patent Identification: U.S. Patent No. 7,127,523, “SPANNING TREE PROTOCOL TRAFFIC IN A TRANSPARENT LAN,” issued October 24, 2006 (the “’523 Patent”).

The Invention Explained

  • Problem Addressed: The patent addresses the problem of preventing data packet loops in Transparent LAN Services (TLS) that span across a provider's core network (Compl. ¶58). Prior art solutions were described as costly, complex to configure, and having security and reliability drawbacks, particularly in separating the provider's network domain from the user's domain (’523 Patent, col. 4:61–col. 5:15).
  • The Patented Solution: The invention proposes a method where Spanning Tree Protocol (STP) control frames, used to detect and prevent network loops, are sent through the same data-plane tunnels (e.g., MPLS LSPs) as the user traffic (’523 Patent, col. 6:2-6). These STP frames are distinguished from user data frames by a "special STP label" (’523 Patent, col. 6:5-6). This allows the provider's routers (LSRs) to process the STP frames and establish a loop-free topology for each TLS within the core network, without forwarding the provider's STP frames to the end-user's equipment, thereby preventing loops irrespective of any user-created loops (’523 Patent, col. 6:6-9).
  • Technical Importance: This technique allowed service providers to offer robust, loop-free Layer 2 VPN services while maintaining a clear separation between the provider's and the customer's network management domains (Compl. ¶59).

Key Claims at a Glance

  • The complaint asserts independent claim 10 (Compl. ¶64).
  • Essential elements of claim 10 (a device claim) include:
    • A communication device (LSR) for use in a TLS.
    • One or more ports for sending/receiving traffic via label-switched tunnels.
    • A traffic processor adapted to transmit control frames (containing a BPDU) to other LSRs via the tunnels.
    • Each control frame comprises a "control traffic label" and a BPDU.
    • The control traffic label indicates to receiving LSRs that STP is to be executed by the LSRs themselves, without transmitting the BPDU to the user's equipment.
    • The traffic processor is also adapted to process received BPDUs to remove loops in the TLS topology.
  • The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 7,283,465 - “HIERARCHICAL VIRTUAL PRIVATE LAN SERVICE PROTECTION SCHEME”

  • Patent Identification: U.S. Patent No. 7,283,465, “HIERARCHICAL VIRTUAL PRIVATE LAN SERVICE PROTECTION SCHEME,” issued October 16, 2007 (the “’465 Patent”).
  • Technology Synopsis: The patent addresses failures in LAN networks by proposing a protection scheme using primary and standby core nodes (virtual bridges) (Compl. ¶¶87-88). The standby node has the same network topology as the primary node it protects, allowing traffic to be redirected to the standby node upon failure of the primary without requiring other network nodes to re-learn MAC table addresses, thus enabling rapid recovery (Compl. ¶88).
  • Asserted Claims: Independent claim 1 is asserted (Compl. ¶92).
  • Accused Features: The NetVanta 1500 Series Ethernet Switch is accused of infringement, specifically through its "ActivChassis" feature, which allegedly creates a virtual switch from multiple devices, including "Master" and "Backup" components that function as the claimed primary and backup virtual bridges (Compl. ¶¶94-97).

U.S. Patent No. 7,768,928 - “CONNECTIVITY FAULT MANAGEMENT (CFM) IN NETWORKS WITH LINK AGGREGATION GROUP CONNECTIONS”

  • Patent Identification: U.S. Patent No. 7,768,928, “CONNECTIVITY FAULT MANAGEMENT (CFM) IN NETWORKS WITH LINK AGGREGATION GROUP CONNECTIONS,” issued August 3, 2010 (the “’928 Patent”).
  • Technology Synopsis: The patent addresses a problem in network maintenance where standard Connectivity Fault Management (CFM) functions cannot properly test individual physical links within a Link Aggregation Group (LAG), because traffic is distributed unpredictably across the links (Compl. ¶116). The solution is a "port definer module" that allows a CFM message to be forwarded over a specific, designated physical link within the LAG, enabling examination of individual link integrity (Compl. ¶117).
  • Asserted Claims: Independent claim 14 is asserted (Compl. ¶121).
  • Accused Features: Defendant’s Total Access 5000 is accused of infringement, with the complaint alleging that it is a system that uses CFM functions to examine aggregated link connections and comprises a "port definer module" that can designate a physical link for forwarding a CFM message (Compl. ¶¶123-126).

U.S. Patent No. 7,983,150 - “VPLS FAILURE PROTECTION IN RING NETWORKS”

  • Patent Identification: U.S. Patent No. 7,983,150, “VPLS FAILURE PROTECTION IN RING NETWORKS,” issued July 19, 2011 (the “’150 Patent”).
  • Technology Synopsis: The patent describes a failure protection mechanism for Virtual Private LAN Services (VPLS) provisioned over ring networks (Compl. ¶146). The solution uses standby connection termination points (CTPs) that connect nodes in the ring to an external network. These standby CTPs are normally blocked to prevent loops but can be activated when nodes detect a ring failure and segmentation, thereby restoring connectivity (Compl. ¶148).
  • Asserted Claims: Independent claim 11 is asserted (Compl. ¶152).
  • Accused Features: Defendant’s NetVanta 8044M Fiber NTE is accused of infringement. It is alleged to be a system that defines a bi-directional ring network using Ethernet Ring Protection Switching (ERPS) and provisions a VPLS over it, utilizing connection termination points that are activated to overcome segmentation upon a failure (Compl. ¶¶154, 159).

III. The Accused Instrumentality

Product Identification

  • ADTRAN NetVanta 3448 Multiservice Access Router and substantially similar products (for the ’669 Patent); ADTRAN NetVanta 4305 and substantially similar products (for the ’523 Patent).

Functionality and Market Context

  • The complaint identifies the NetVanta 3448 as a router that performs data transmission and supports protocols such as Multilink PPP (MLPPP) (Compl. ¶¶22, 25). Its functionality allegedly includes fragmenting data frames into smaller pieces and interleaving high-priority packets with fragments of lower-priority packets using Quality of Service (QoS) maps to reduce delay for streaming protocols (Compl. ¶¶24, 25, 27). The complaint provides a product datasheet describing the NetVanta 3448 as a multiservice access router with "RapidRoute technology for greater performance" (Compl. p. 7).
  • The NetVanta 4305 is identified as a communication device that operates as a label-switched router (LSR) within a transparent local area network service (TLS) (Compl. ¶65). It is alleged to use label-switched tunnels and to support Spanning Tree Protocol (STP) to manage network topology and remove loops (Compl. ¶¶65, 67). A network diagram from Defendant's materials is included, which illustrates a topology with "label switched tunnels between label switched routers" (Compl. p. 38).
  • The complaint alleges these products are part of Defendant's broader portfolio of telecommunications equipment, which is developed, manufactured, and distributed by ADTRAN (Compl. ¶17, ¶60).

IV. Analysis of Infringement Allegations

’669 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a method for transmitting data over a channel, comprising: receiving a first datagram for transmission at a first priority; The NetVanta 3448 router receives a first datagram for transmission at a first priority. The complaint provides a diagram from ADTRAN documentation showing fragmentation in MLPPP (Compl. p. 9). ¶23 col. 3:36-38
and receiving a second datagram for transmission at a second priority, higher than the first priority, before the transmission of the first datagram is completed; The router receives a second, higher-priority datagram before the first is fully transmitted. Priority is allegedly defined using Quality of Service (QoS) maps. ¶24 col. 3:39-42
responsive to receiving the second datagram, deciding to divide the first datagram into a plurality of fragments, including a first fragment and a last fragment; The router responds to the second datagram by deciding to divide the first datagram into fragments, allegedly using MLPPP to fragment frames into smaller pieces. ¶25 col. 3:43-46
transmitting the fragments of the first datagram over the channel, beginning with the first fragment; The router is configured to transmit the fragments of the first datagram, beginning with the first fragment. ¶26 col. 3:47-49
and transmitting at least a fragment of the second datagram over the channel before transmitting the last fragment of the first datagram. The router is configured to transmit a fragment of the high-priority second datagram before transmitting the final fragment of the first datagram, a feature referred to as "interleave." ¶27 col. 3:50-53
wherein transmitting at least the fragment of the second datagram comprises interrupting transmission of a number of datagrams, including at least the first datagram, ... The transmission of the second datagram fragment allegedly comprises interrupting the transmission of the first datagram in order to transmit the higher-priority fragment. ¶28 col. 4:24-29
and adding a field to the fragment indicating the number of datagrams whose transmission has been interrupted. The router is alleged to include headers (fragmentation, PPP, etc.) that include fields indicating the number of fragments or datagrams whose transmission is interrupted. ¶¶29-30 col. 4:24-29

Identified Points of Contention

  • Technical Question: The complaint's allegation for the final "adding a field" element states that various headers include fields indicating the number of fragments whose transmission is interrupted, while the claim requires a field indicating the number of datagrams interrupted (Compl. ¶¶29-31). The analysis may focus on whether the accused product's headers perform the specific function required by the claim language, an issue the complaint notes may require source code review (Compl. ¶32).
  • Scope Question: The claim recites "datagrams," a term often associated with IP networks, while the complaint's evidence centers on the fragmentation of "frames" in MLPPP (Compl. ¶25). A potential dispute may arise over whether the term "datagram" as used in the patent can be construed to cover the "frames" processed by the accused router.

’523 Patent Infringement Allegations

Claim Element (from Independent Claim 10) Alleged Infringing Functionality Complaint Citation Patent Citation
A communication device for operation as one of a plurality of label-switched routers (LSRs) in a transparent local area network service (TLS), which includes a system of label-switched tunnels between the label-switched routers (LSRs) through a communication network... The NetVanta 4305 is alleged to be a communication device for operation as an LSR in a TLS, which includes a system of label-switched tunnels. A supporting diagram shows "label switched tunnels between label switched routers" (Compl. p. 38). ¶65 col. 5:61-64
one or more ports, adapted to send and receive traffic via the label-switched tunnels; and The device is alleged to comprise one or more ports adapted to send and receive traffic via the label-switched tunnels. ¶66 col. 7:32-34
a traffic processor... adapted to transmit control frames to the LSRs in the TLS via the label-switched tunnels, each control frame comprising a control traffic label and a bridge protocol data unit (BPDU) in accordance with a spanning tree protocol (STP), the control traffic label indicating to the LSRs that the STP is to be executed by the LSRs without transmission of the BPDU to the user equipment... The device's traffic processor is alleged to transmit control frames (containing BPDUs for STP) via the tunnels. The complaint alleges the "control traffic label" indicates to the LSRs that STP is to be executed by them without transmission of the BPDU to user equipment. ¶67 col. 7:40-49
wherein the traffic processor is further adapted, upon receiving the control frames, to process the BPDU, responsively to the control traffic label, so as to remove loops in a topology of the TLS irrespective of the user equipment. The device's traffic processor is alleged to process received BPDUs in response to the control traffic label in order to remove loops in the TLS topology, irrespective of user equipment. ¶67 col. 7:50-54

Identified Points of Contention

  • Scope Question: A central issue may be the construction of "control traffic label." The infringement theory depends on whether the accused router's mechanism for handling and processing STP BPDUs within the TLS constitutes the specific "control traffic label" required by the claim, which must indicate that the provider's LSRs—and not the customer's equipment—are to execute STP.
  • Technical Question: The complaint alleges the accused device performs the claimed functions, but provides limited detail on how the device's standard STP implementation performs the specific function of the "control traffic label." The analysis will likely require evidence detailing the precise interaction between the device's traffic processor, its handling of BPDUs, and how this prevents transmission of those BPDUs to user equipment.

V. Key Claim Terms for Construction

For the ’669 Patent

  • The Term: "datagram"
  • Context and Importance: The scope of this term is critical because the accused product is described in the complaint's supporting documents as operating on "frames" within the MLPPP protocol (Compl. ¶25). Whether "datagram" is construed broadly to cover any packet-switched unit of data or narrowly to mean a specific type, such as an IP datagram, may be dispositive of infringement.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent uses "datagrams" and "packets" interchangeably, stating in the abstract that the invention relates to "datagrams, typically data packets." The detailed description also refers generally to "transmitting data over a channel" (’669 Patent, Abstract; col. 3:32), suggesting the specific data unit type may not be limiting.
    • Evidence for a Narrower Interpretation: The specification mentions "Internet Protocol (IP) packets" as an example of datagrams received (’669 Patent, col. 3:45-46), which could be used to argue that the term is tied to the IP context.

For the ’523 Patent

  • The Term: "control traffic label"
  • Context and Importance: This term appears to be the point of novelty. The infringement analysis will turn on whether the accused product's mechanism for handling BPDUs in a TLS network meets the claim's functional requirement: that the "label" indicates to LSRs that they should execute STP without forwarding the BPDU to the customer. Practitioners may focus on this term because standard STP implementations may not explicitly use a "label" for this purpose.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The claim language is functional, describing what the label does ("indicating to the LSRs..."). This may support a construction where any mechanism that achieves this signaling function, regardless of its specific form, meets the limitation.
    • Evidence for a Narrower Interpretation: The specification describes the invention in the context of MPLS, repeatedly referencing a "special STP label" or "BPDU identifying label" that is pushed onto the MPLS label stack to distinguish it from user data (’523 Patent, col. 6:5-6; FIG. 3). This could support an argument that the term is limited to a distinct label added to a packet's label stack.

VI. Other Allegations

  • Indirect Infringement: For all asserted patents, the complaint alleges induced infringement based on Defendant's affirmative acts of providing datasheets, technical guides, installation guides, and other support materials that allegedly instruct customers and end-users on how to configure and use the accused products in an infringing manner (Compl. ¶¶38, 40; ¶¶73, 75). Contributory infringement is also alleged, on the basis that the accused products are not suitable for substantial non-infringing use (Compl. ¶39, ¶74).
  • Willful Infringement: The complaint alleges willful infringement for all five patents. The basis for willfulness includes alleged pre-suit knowledge from notice letters sent in 2017 (Compl. ¶33, ¶68, ¶102, ¶127, ¶160) and post-suit knowledge from the service of the original complaint (Compl. ¶34, ¶69, ¶103, ¶128, ¶163). For the ’150 Patent, the willfulness allegation is further supported by claims of a 2019 infringement judgment against ADTRAN in Germany on a corresponding European patent, after which Defendant allegedly continued its infringing conduct (Compl. ¶¶161-162, 165).

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of definitional scope: can claim terms rooted in specific patent embodiments, such as the "control traffic label" of the ’523 Patent, be construed broadly enough to read on the functionality of industry-standard protocols like STP as implemented in the accused products? Similarly, does the term "datagram" in the ’669 Patent encompass the MLPPP "frames" handled by the accused router?
  • A key evidentiary question will be one of functional proof: what evidence will demonstrate that the accused products perform the specific, and in some cases complex, functions required by the claims? For example, does the accused router's header for the '669 Patent infringement claim contain a field that tracks the number of interrupted datagrams, as claimed, or does it merely contain sequencing information for reassembly? The complaint's own acknowledgment that source code review may be necessary underscores that this will be a central factual dispute.
  • A significant question for damages and willfulness, particularly regarding the ’150 Patent, will be the impact of foreign litigation: what legal weight, if any, will be given to the alleged German court's finding that ADTRAN infringed a corresponding European patent? Plaintiff will likely argue this establishes egregious conduct, while Defendant may argue it is irrelevant to infringement under U.S. law.