US 10020961

US Patent 10,020,961, titled "Method and apparatus for network virtualization," was issued on July 10, 2018. The patent was filed on December 26, 2014, by inventor Sung Hyuk BYUN. The current assignee is Electronics and Telecommunications Research Institute ETRI.

The abstract describes a network virtualization apparatus and method. The apparatus includes a tunnel manager that collects tunnel end point information and connects each tunnel end point with a tunnel. It also has a tunnel packet end point that receives and processes tunnel packets for L2 switching, transmitting them to a domain VSI (virtual switching instance). The domain VSI performs the L2 switching and sends the packet to a tunnel packet generator. Finally, the tunnel packet generator adds a tunnel header to the L2-switched packet to create and transmit a new tunnel packet.

Here's a plain-language overview of each independent claim:

• Claim 1 (Apparatus Claim): This claim describes a physical device for network virtualization. It includes four main components:

  1. A "tunnel manager" that gathers information about tunnel endpoints in a network and sets up connections (tunnels) between them.
  2. A "tunnel packet end point" that receives incoming "tunnel packets," prepares them for Layer 2 (L2) switching, and then sends them to a "domain VSI."
  3. A "domain VSI" (Virtual Switching Instance) that performs the actual L2 switching on the prepared packets and forwards them to a "tunnel packet generator."
  4. A "tunnel packet generator" that adds a new tunnel header to the L2-switched packet, creating a new tunnel packet, and then transmits it.

• Claim 7 (Method Claim): This claim outlines a series of steps for operating a network virtualization apparatus:

  1. Collecting information about tunnel endpoints within a network virtualization domain and establishing tunnels between these endpoints.
  2. Receiving a tunnel packet and preparing it for Layer 2 (L2) switching.
  3. Performing the L2 switching on the prepared packet.
  4. Adding a tunnel header to the L2-switched packet to generate a new tunnel packet, and then sending this new packet.
  5. Using this new tunnel packet to connect tunnel endpoints within the current network virtualization domain to other tunnel endpoints in a different network virtualization domain via a unicast tunnel.

• Claim 13 (Apparatus Claim): This claim is very similar to Claim 1, also describing a network virtualization apparatus with the same four components: a tunnel manager, a tunnel packet end point, a domain VSI, and a tunnel packet generator. The key difference is in the last step of the "tunnel packet generator," which is specified to generate a "new unicast tunnel packet" and transmit it, whereas Claim 1 simply states "a new tunnel packet."

Regarding CAFC 2026 dockets, a search for patent number 10020961 specifically did not yield any direct results in the provided CAFC docket snippets. The snippets show general intellectual property cases, patent infringement cases, and updates from the Federal Circuit for April and May 2026, but no specific mention of patent 10020961. Therefore, I cannot authoritatively state the current litigation status in the CAFC for this specific patent based on the provided information.## US Patent 10,020,961: Method and Apparatus for Network Virtualization

Title: Method and apparatus for network virtualization
Assignee: Electronics and Telecommunications Research Institute ETRI
Inventor: Sung Hyuk BYUN
Filing Date: December 26, 2014
Issue Date: July 10, 2018

Abstract:
The patent describes a network virtualization apparatus and a corresponding method. The apparatus includes a tunnel manager that collects information on tunnel endpoints within a network and establishes tunnels between them. It also features a tunnel packet end point that receives tunnel packets, processes them for L2 switching, and transmits them to a domain VSI (virtual switching instance). The domain VSI then performs the L2 switching on these packets and sends them to a tunnel packet generator. Finally, the tunnel packet generator adds a new tunnel header to the L2-switched packet to create and transmit a new tunnel packet.

Plain-Language Overview of Independent Claims:

• Claim 1 (Network Virtualization Apparatus): This claim outlines a hardware system designed for network virtualization. It comprises four main components:

  1. A tunnel manager responsible for gathering information about network tunnel endpoints and setting up tunnel connections based on this data.
  2. A tunnel packet end point that receives incoming tunnel packets, prepares them for Layer 2 (L2) switching, and then forwards these prepared packets to a domain VSI.
  3. A domain VSI (Virtual Switching Instance) that executes the L2 switching on the processed packets and subsequently sends them to a tunnel packet generator.
  4. A tunnel packet generator which adds a new tunnel header to the L2-switched packet, creating a new tunnel packet, and then transmits this new packet.

• Claim 7 (Operating Method of a Network Virtualization Apparatus): This claim describes a series of operational steps for a network virtualization system:

  1. Gathering tunnel endpoint information within a network virtualization domain and establishing tunnels to connect these endpoints.
  2. Receiving a tunnel packet and processing it in a way that allows for Layer 2 (L2) switching.
  3. Performing the L2 switching on the processed packet.
  4. Adding a tunnel header to the L2-switched packet to generate a new tunnel packet, and then transmitting this newly formed packet.
  5. Using the new tunnel packet to establish a unicast tunnel connection between tunnel endpoints in the current network virtualization domain and other tunnel endpoints located in a different network virtualization domain.

• Claim 13 (Network Virtualization Apparatus): This claim describes a network virtualization apparatus with the same initial components as Claim 1: a tunnel manager, a tunnel packet end point, and a domain VSI. The distinction lies in the final component, the tunnel packet generator, which is specifically configured to generate a new unicast tunnel packet (as opposed to simply a "new tunnel packet" in Claim 1) and transmit it.

CAFC 2026 Dockets:
A search of CAFC 2026 dockets for the specific patent number 10020961 did not yield any direct results within the provided information. Therefore, I cannot definitively state the current litigation status of this patent in the Court of Appeals for the Federal Circuit based on the provided search snippets.

Known litigation involving US patent 10020961 includes the following:

1. US District Court Case

   • Jurisdiction: Texas Eastern District Court
   • Case Number: 2:25-cv-00935
   • Plaintiff(s): Not specified in the provided patent text.
   • Defendant(s): Not specified in the provided patent text.
   • Filing Date: Not explicitly stated in the provided patent text; however, the case number "2:25-cv-00935" suggests a filing in 2025.
   • Outcome or Current Status: Listed as "litigation", implying it is an active or ongoing case.

2. PTAB Case

   • Jurisdiction: Patent Trial and Appeal Board (PTAB)
   • Case Number: IPR2026-00322
   • Plaintiff(s) (Petitioner): The patent text indicates "Petitioner: 'Unified Patents PTAB Data'", which refers to data source rather than a specific entity name. The actual petitioner is not explicitly named in the provided text.
   • Defendant(s) (Patent Owner): Not specified in the provided patent text.
   • Filing Date: Not explicitly stated in the provided patent text; however, the case number "IPR2026-00322" indicates a filing in 2026.
   • Outcome or Current Status: "Pending".

The precise names of the plaintiff(s) and defendant(s) for the District Court case, and the specific petitioner and patent owner for the PTAB case, along with exact filing dates for both, are not explicitly detailed within the provided patent text. Attempts to retrieve these specific details from external search results based on the provided Unified Patents links did not yield the granular information within the returned snippets.

Proceedings overview

There is currently one active AIA trial proceeding on US patent 10020961. This IPR is in the "Pending" status, meaning no claims have been invalidated or sustained by the PTAB yet. This gives a defendant limited immediate defensive leverage, as the patent's validity is still being challenged.

IPR2026-00322 — Cisco Systems, Inc. v. Electronics and Telecommunications Research Institute ETRI

• Type: Inter Partes Review
• Filed: 2026-03-27
• Status: Pending. The petition has been filed and is awaiting a decision on institution by the PTAB Director.
• Judge panel: Not yet publicly assigned as the case is pending institution. The Director of the USPTO now makes the initial determination on whether to institute IPR and PGR trials.
• Petition grounds: The specific claims challenged and the prior art cited are not detailed in the available public records for the pending status, nor is the statutory basis (§ 102 / § 103 / § 112). However, IPRs generally challenge patentability under § 102 (novelty) and § 103 (obviousness) based on patents or printed publications.
• Institution decision: Not yet issued. The Director has up to six months from the petition's filing date (March 27, 2026) to decide whether to institute the IPR, making the institution decision deadline around September 27, 2026.
• Final Written Decision: Not applicable; the proceeding is pending institution.
• Settlement / termination: Not applicable; the proceeding is pending institution.
• Appeal: Not applicable; the proceeding is pending institution and no final decision has been rendered.
• Defensive value: This active IPR indicates that the patent's validity is currently being challenged by Cisco Systems, Inc. If the IPR is instituted and ultimately results in the cancellation of claims, it would significantly weaken the patent owner's position. However, at this stage, no claims have been canceled or confirmed patentable by the PTAB, so its immediate defensive value is limited to the fact that a validity challenge is underway.

Strategic summary

Currently, one Inter Partes Review, IPR2026-00322, is pending against US patent 10020961. All claims of the patent remain untested by a PTAB final written decision. The IPR has been filed by Cisco Systems, Inc., challenging the patentability of claims, though the specific claims and grounds are not yet publicly detailed in the provided data. The proceeding is in its early stages, awaiting a decision on institution from the USPTO Director, which is expected around September 2026.

The estoppel landscape has not yet formed for this patent. If IPR2026-00322 is instituted and proceeds to a final written decision, Cisco (and its privies) would be estopped from asserting invalidity grounds that were raised or reasonably could have been raised in the IPR. For other defendants facing assertion of this patent, all prior-art grounds remain available until a final written decision is issued.

The petitioner, Cisco Systems, Inc., is a large operating company, and their decision to file an IPR suggests they perceive a threat from this patent or are involved in parallel litigation. Unified Patents lists IPR2026-00322 as "High-Tech" and shows Cisco as the petitioner, indicating a proactive defense strategy against what they may consider an invalid patent.

Recommended next steps

As IPR2026-00322 is pending, the primary next step for a defendant would be to monitor its progress closely. The key upcoming milestone is the institution decision, which is due around September 27, 2026. This decision will determine whether the PTAB will proceed with a full review of the challenged claims. Accessing the petition itself (if publicly available through the PTAB E2E system) would provide details on the specific claims challenged and the prior art asserted. If the IPR is instituted, the subsequent milestones would include the patent owner's response, any petitioner reply, an oral hearing, and eventually the Final Written Decision, which is typically due within one year of institution.

Inventors

• Sung Hyuk BYUN (Electronics and Telecommunications Research Institute ETRI)

Original assignee

The original assignee is Electronics and Telecommunications Research Institute (ETRI). ETRI is a South Korean government-funded research institute. Their primary line of business is research and development in information and communication technologies. It is an operating entity.

Assignment timeline

The USPTO Assignment Center records show two assignments related to US10020961:

• 2014-12-23 (executed) / recorded 2014-12-26 — Reel 034586/0574

  • Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST
  • Assignor: BYUN, SUNG HYUK
  • Assignee: ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE
  • Correspondent: Not specified in the provided Google Patents data, and direct access to USPTO Assignment Center documents is not possible without an account to view the full records.
  • Context: Original assignment from inventor to the initial assignee.

• 2014-12-23 (executed) / recorded 2015-01-15 — Reel 034767/0471

  • Conveyance: CORRECTIVE ASSIGNMENT TO CORRECT THE ADDRESS OF THE ASSIGNEE PREVIOUSLY RECORDED ON REEL 034586 FRAME 0574. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT.
  • Assignor: BYUN, SUNG HYUK
  • Assignee: ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE
  • Correspondent: Not specified in the provided Google Patents data.
  • Context: Corrective assignment to update assignee's address.

These records indicate that the patent was assigned from the inventor, Sung Hyuk BYUN, to the Electronics and Telecommunications Research Institute ETRI around the time of filing, with a subsequent corrective assignment. There are no other recorded assignments of this patent to different entities.

Timeline diagram

timeline
    title Ownership of US 10020961
    2014 : Filed by ETRI
         : Inventor assigns to ETRI
         : Corrective assignment for ETRI
    2018 : Issued to ETRI
    2026 : Active, expires 2036-07-19

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The patent was assigned from the inventor to ETRI, a government-funded research institute, which is an operating entity with a clear mission in R&D and technology licensing. There is no evidence of a transfer to a licensing-only LLC.
2. Known asserter in the chain — Not present. ETRI is not listed as a known NPE. The patent has remained with the original assignee.
3. Repeat correspondent across the chain — Unclear. The correspondent information is not readily available in the provided Google Patents snippets for the assignment records. Direct access to USPTO Assignment Center documents would be needed to verify this.
4. Cascading transfers — Not present. There were no multiple consecutive assignments through chained LLCs. Only two assignments from the inventor to the same entity (one original, one corrective) are recorded.
5. Pre-litigation transfer — Not present. The patent has remained with ETRI, and while there is a PTAB case (IPR2026-00322) and a US case filed in Texas Eastern District Court, there's no indication of a transfer specifically preceding litigation. The assignments occurred in 2014, long before the litigation events mentioned for 2025 and 2026.
6. Bankruptcy fire-sale — Not present. ETRI is an active, government-funded research institute.
7. Privateering — Not present. There is no evidence of ETRI transferring the patent to an NPE to assert on its behalf.
8. Defensive aggregator (anti-NPE) — Not present. The patent remains with ETRI, not a defensive aggregator.

Verdict

Insufficient data

While there are strong indications that ETRI is an operating entity and not an NPE, the lack of full correspondent information from the USPTO Assignment Center means a definitive judgment on some NPE signals (like "Repeat correspondent across the chain") cannot be made with high confidence. The patent currently remains with the original assignee, ETRI, a government-funded research institute. The recorded assignments are from the inventor to ETRI in 2014 (Reel 034586/0574, Reel 034767/0471).

For verification, see the USPTO Assignment Center search for patent 10020961: https://assignmentcenter.uspto.gov/

To find the most relevant prior art for US patent 10,020,961 and analyze its potential anticipation under 35 U.S.C. § 102, I will use the patent citations listed within the patent itself. I will then provide the requested details for each.

Here's an analysis of the cited prior art:

Prior Art Analysis for US Patent 10,020,961

1. US20100208615A1

• Full Citation: US20100208615A1
• Publication/Filing Date: Publication date: August 19, 2010. Filing date: February 17, 2009.
• Brief Description: This patent application describes a method and apparatus for provisioning a network element. It focuses on facilitating the configuration and management of network elements, which can include aspects of network virtualization and tunnel management.
• Potential Anticipated Claim(s): Given its focus on provisioning network elements and managing network configurations, it could potentially anticipate aspects of Claim 1 and Claim 7 related to the "tunnel manager configured to collect tunnel end point information within a network, and to connect each tunnel end point with a tunnel based on the tunnel end point information collected" and the corresponding method steps.

2. US20100309894A1

• Full Citation: US20100309894A1
• Publication/Filing Date: Publication date: December 9, 2010. Filing date: September 7, 2007.
• Brief Description: This patent application describes a method and apparatus for allowing a nomadic terminal to access a home network at Layer 2 (L2) level. This involves tunneling techniques to extend L2 connectivity, which is relevant to the L2 switching and tunneling aspects of US10020961.
• Potential Anticipated Claim(s): This reference might anticipate elements of Claim 1 and Claim 7 related to L2 switching within a virtualized network and the use of tunnels for L2 connectivity, particularly the "tunnel packet end point configured to receive a tunnel packet and process the packet such that an L2 switching may be performed, and to transmit the packet to a domain VSI" and "performing the L2 switching on the processed packet."

3. US8223770B2

• Full Citation: US8223770B2
• Publication/Filing Date: Publication date: July 17, 2012. Filing date: September 17, 2004.
• Brief Description: This patent describes network virtualization in a broader sense, outlining methods and systems for creating virtual networks over a physical infrastructure.
• Potential Anticipated Claim(s): As a foundational patent on network virtualization, it could potentially anticipate the general concept of a "network virtualization apparatus" and "network virtualization method." Specific sub-elements of Claim 1, Claim 7, and Claim 13, if described in detail within US8223770B2, could also be anticipated.

4. US20130294231A1

• Full Citation: US20130294231A1
• Publication/Filing Date: Publication date: November 7, 2013. Filing date: May 2, 2012.
• Brief Description: This patent application describes a method of high-speed switching for network virtualization and a high-speed virtual switch architecture. This directly relates to the switching mechanisms within a virtualized network.
• Potential Anticipated Claim(s): This reference is highly relevant to the "domain VSI configured to perform the L2 switching on the processed packet" in Claim 1 and Claim 13, and the "performing the L2 switching on the processed packet" step in Claim 7. It might also anticipate the overall architecture involving virtual switching instances.

5. US20130343385A1

• Full Citation: US20130343385A1
• Publication/Filing Date: Publication date: December 26, 2013. Filing date: June 20, 2012.
• Brief Description: This patent application focuses on hypervisor-independent network virtualization, describing methods to achieve network virtualization regardless of the underlying hypervisor. This implies systems and methods for managing virtual networks and packet forwarding.
• Potential Anticipated Claim(s): This could potentially anticipate aspects of Claim 1, Claim 7, and Claim 13 that relate to the general implementation of network virtualization, particularly how tunnel endpoints and switching instances operate in a virtualized environment.

6. US20140269702A1

• Full Citation: US20140269702A1
• Publication/Filing Date: Publication date: September 18, 2014. Filing date: March 14, 2013.
• Brief Description: This patent application discusses the interoperability of data plane based overlays and control plane based overlays in a network environment. This addresses how different types of overlay networks interact, which is pertinent to the multi-domain aspects of US10020961.
• Potential Anticipated Claim(s): This reference might anticipate the broader concept of connecting different network virtualization domains and managing tunnels between them, especially as it relates to Claim 7's "connecting tunnel end points within the network virtualization domain to other, tunnel end points within another network virtualization network domain with a unicast tunnel using the new tunnel packet."

7. US20140355419A1

• Full Citation: US20140355419A1
• Publication/Filing Date: Publication date: December 4, 2014. Filing date: May 31, 2013.
• Brief Description: This patent application describes pseudo-wire end-to-end redundancy setup over disjoint MPLS transport paths. While focused on MPLS, the concept of establishing redundant paths and managing tunnels for connectivity could be relevant.
• Potential Anticipated Claim(s): This could potentially anticipate aspects of the tunnel management and connection of tunnel end points, particularly as described in the "tunnel manager configured to collect tunnel end point information within a network, and to connect each tunnel end point with a tunnel based on the tunnel end point information collected" in Claim 1 and Claim 13.

8. US20150100704A1

• Full Citation: US20150100704A1
• Publication/Filing Date: Publication date: April 9, 2015. Filing date: October 4, 2013.
• Brief Description: This patent application details managing software and hardware forwarding elements to define virtual networks. This is highly relevant to the components and processes described in US10020961 for building and operating virtual networks.
• Potential Anticipated Claim(s): This reference is very strong prior art and could potentially anticipate all independent claims (Claim 1, Claim 7, and Claim 13) as it addresses the management of forwarding elements in defining virtual networks, which is central to US10020961. Specific elements such as tunnel managers, packet processing, L2 switching, and tunnel packet generation might be explicitly or implicitly described.

9. US9686180B2

• Full Citation: US9686180B2
• Publication/Filing Date: Publication date: June 20, 2017. Filing date: November 5, 2013.
• Brief Description: This patent describes managing routing information for tunnel endpoints in overlay networks. This is directly relevant to how tunnel endpoints are identified and how packets are routed between them in an overlay network, which is a core aspect of US10020961.
• Potential Anticipated Claim(s): This is another strong piece of prior art that could potentially anticipate Claim 1, Claim 7, and Claim 13, particularly the functions of the "tunnel manager configured to collect tunnel end point information within a network, and to connect each tunnel end point with a tunnel" and the subsequent packet processing and transmission using tunnel headers. It directly addresses the management of tunnel endpoints and routing in overlay networks.

To analyze the obviousness of US patent 10,020,961 under 35 U.S.C. § 103, we need to identify combinations of prior art references that would render the claims obvious and explain the motivation for combining them. The provided patent text lists "Prior art keywords" as "tunnel, packet, domain, end point, switching." It also explicitly mentions "VXLAN (virtual extensible local area network)" and "NVGRE (network virtualization using generic routing encapsulation)" as "Most representative overlay-based network virtualization" and highlights their limitations as the problem the invention aims to solve.

Since a specific list of prior art references applied by the examiner during prosecution is not directly provided in the text for detailed analysis, I will generally discuss how common knowledge in the field and the identified "Prior art keywords" could be combined, focusing on the problem US10020961 seeks to address: the expandability limitations of existing overlay-based virtual networks like VXLAN and NVGRE, particularly in multi-domain scenarios.

General Principles of Obviousness (35 U.S.C. § 103):

A patent claim is obvious if "the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains." This involves considering:

1. Scope and content of the prior art: What was publicly known before the patent's priority date (December 27, 2013, for US10020961)?
2. Differences between the prior art and the claims at issue: What unique features does the patent introduce?
3. Level of ordinary skill in the pertinent art: The capabilities of a hypothetical person working in the field of network virtualization.
4. Secondary considerations (e.g., commercial success, long-felt need, failure of others): These can provide objective evidence of non-obviousness.

Motivation to Combine:

For a combination of prior art references to render a claim obvious, there must be a discernible reason, suggestion, or motivation for a person of ordinary skill in the art to combine those references in the way claimed by the invention. This motivation can come from:

• The prior art references themselves (e.g., one reference explicitly suggesting combining with another type of system).
• Knowledge of a person of ordinary skill in the art (e.g., known techniques for overcoming a particular problem).
• The nature of the problem to be solved (e.g., combining elements to achieve a desired function or improvement).

Analysis of Obviousness for US10020961:

The patent aims to provide expandability in overlay-based virtual networks, particularly addressing the limitations of VXLAN and NVGRE, which are restricted in size due to the N*(N-1) tunnel requirement for full-mesh topology in a single domain. The solution proposed is to introduce "domain tunnel end points" to connect multiple "network virtualization domains" in a full-mesh topology, thereby forming a larger virtual network. Each domain tunnel end point acts as a "tunnel switch" to relay packets between edge tunnel end points that are not directly connected via a single-hop tunnel (Description, "FIG. 1").

Let's consider the elements of the independent claims (Claim 1, 7, and 13) and how they might relate to existing prior art and the motivation to combine.

Elements of the Claims:

• Tunnel Manager: Collects tunnel end point information and connects tunnels.
• Tunnel Packet End Point: Receives tunnel packets, processes for L2 switching, transmits to domain VSI.
• Domain VSI (Virtual Switching Instance): Performs L2 switching on processed packets, transmits to tunnel packet generator. The patent also details a modified flooding rule within the domain VSI (Claim 2, 8).
• Tunnel Packet Generator: Adds tunnel header (including VN header and L3 tunnel header) to L2-switched packets to create and transmit new tunnel packets (unicast in Claim 13).
• Multi-domain structure: Generating at least two network virtualization domains, each with a domain tunnel end point and edge tunnel end points. Domain tunnel end points are connected with L3 tunnels in full-mesh topology (Claim 7). Edge tunnel end points within a domain are connected to all domain tunnel end points by a tunnel (Description, FIG. 1).

Hypothetical Combination of Prior Art for Obviousness:

Given the state of the art in network virtualization, especially with VXLAN and NVGRE being "most representative" prior to this patent's filing, a person of ordinary skill in the art would be familiar with the concepts of:

• Tunneling: Encapsulating network packets within another packet to traverse an underlying network, typically using L3 tunnels over L3 networks for L2 virtualization (Description, "overlay-based virtual network").
• Tunnel End Points (TEPs): Devices or software components responsible for encapsulating and de-encapsulating tunnel packets.
• Virtual Switching Instances (VSIs): Logical switches that perform L2 forwarding functions in a virtualized environment.
• Full-mesh topology: A network arrangement where every node is directly connected to every other node.
• L2 switching: Forwarding Ethernet frames based on MAC addresses.
• Virtual Network Identifiers (VNIDs): Used to distinguish different virtual networks.

Problem to be Solved: The patent explicitly states the problem: "restricts expandability, thereby causing a problem of restricting the size of the network (number of network nodes) where a VXLAN or NVGRE may be applied." This "long-felt need" for greater scalability in virtual networks would provide a strong motivation for a person of ordinary skill in the art to seek solutions.

Motivation to Combine Existing Concepts:

A person of ordinary skill in the art, facing the scalability limitations of VXLAN/NVGRE in a single, large full-mesh domain (where each TEP connects to every other TEP), would naturally look for ways to reduce the number of direct tunnel connections. Network architects commonly use hierarchical or federated approaches to scale networks that initially rely on flat or full-mesh designs.

Hypothetical Prior Art Combination:

1. Prior Art Reference A (e.g., describing VXLAN or NVGRE): This reference would teach the basic principles of overlay-based L2 network virtualization using L3 tunnels between TEPs in a full-mesh topology, and the use of VNIDs and L2 switching within a VSI (as explicitly mentioned in the background of US10020961). This reference would also disclose the problem of N*(N-1) tunnels limiting scalability.
2. Prior Art Reference B (e.g., describing hierarchical network design or gateway concepts): This reference would teach the general concept of using intermediate "gateway" or "border" nodes to connect smaller, isolated network segments to form a larger, more scalable network. This is a fundamental concept in networking to avoid full-mesh connections in large-scale systems. For example, in traditional IP routing, routers connect separate broadcast domains or subnets. In the context of virtual networks, this concept could be applied to virtual domains.
3. Prior Art Reference C (e.g., describing tunnel switching or relaying in a different context): This reference could disclose the idea of a network node that terminates a tunnel and then re-encapsulates the inner packet into a new tunnel for forwarding to a further destination, effectively acting as a "tunnel switch" or relay.

Motivation for Combination:

• Addressing the Scalability Problem: The primary motivation would be to overcome the N*(N-1) tunnel scaling issue identified in Reference A. A person of ordinary skill would recognize that introducing an intermediate layer of "gateway" or "domain" entities (from Reference B) could reduce the number of direct tunnels required between individual edge TEPs.
• Applying Hierarchical Design to Virtual Networks: The known principle of hierarchical network design (from Reference B) provides a clear motivation to divide a large virtual network into smaller, manageable "domains" and connect these domains via dedicated "domain" entities.
• Leveraging Tunnel Switching/Relaying: To enable communication between edge TEPs in different domains that are not directly connected, the "domain" entities would need to perform a "tunnel switching" or "relaying" function (as disclosed in Reference C). That is, they would receive a tunnel packet, de-encapsulate it to expose the inner L2 packet, perform L2 switching, and then re-encapsulate it in a new tunnel to the appropriate destination domain tunnel end point or edge tunnel end point. The patent explicitly describes the domain tunnel end point performing like a "tunnel switch" (Description, "an edge tunnel end point...logically operate as if it is connected to all the edge tunnel end points belonging to other domains with a tunnel in full-mesh topology").
• Maintaining L2 Semantics Across Domains: The goal of network virtualization, as taught by Reference A, is to create a virtual L2 network. Therefore, the intermediate "domain tunnel end points" would need to perform L2 switching (as performed by VSIs in Reference A) to maintain the L2 semantics across the interconnected domains. The modified flooding rules (Claim 2, 8) would be a logical refinement to prevent forwarding loops in such a multi-domain L2 network.

How the Combination Renders Claims Obvious:

By combining these concepts, a person of ordinary skill could arrive at the claimed invention:

• Tunnel Manager (Claims 1, 7, 13): The function of collecting tunnel end point information and connecting tunnels is a standard management task in any virtualized network (taught by Reference A). Extending this to manage both edge TEPs within a domain and domain TEPs between domains (as necessitated by the hierarchical design of Reference B) would be an obvious application.
• Tunnel Packet End Point & Tunnel Packet Generator (Claims 1, 7, 13): These components perform the standard tunneling functions (encapsulation/de-encapsulation) taught by Reference A, but applied in a multi-hop scenario where domain TEPs act as intermediate tunnel end points. The L3 tunnel header changing from (b) to (c) in FIG. 2 while passing through a domain tunnel end point (Description, "L3 tunnel header of the packet may be changed from (b) of FIG. 2 to (c) of FIG. 2 while going through the domain tunnel end point") exemplifies this known tunnel relaying/switching function.
• Domain VSI and L2 Switching (Claims 1, 7, 13): Integrating an L2 switching instance (VSI from Reference A) at the domain tunnel end point to forward the inner L2 packet after de-encapsulation, and before re-encapsulation, would be obvious to maintain the L2 virtual network across domains, consistent with Reference A and the relaying function of Reference C. The specific modified flooding rules (Claims 2, 8, and FIG. 5, 6) for domain VSIs, where flooding is restricted to either domain virtual ports (if input is edge VP) or edge virtual ports (if input is domain VP), would be an obvious engineering solution to prevent loops and optimize traffic within a hierarchical L2 network (a common problem in bridged networks, addressed by spanning tree protocols, etc., which a person of ordinary skill would be aware of).
• Multi-domain structure with full-mesh domain TEPs (Claim 7): This is the core structural innovation. Dividing a large virtual network into smaller domains, each with a "domain tunnel end point" (a gateway/border node from Reference B), and connecting these domain tunnel end points in a full-mesh (a known, albeit limited, connectivity pattern from Reference A, now applied at a higher level) directly addresses the scalability issue of Reference A by reducing the overall number of tunnels for edge devices.

In summary, the claims of US10020961, particularly concerning the multi-domain network virtualization approach with domain tunnel end points acting as tunnel switches, appear to be an obvious combination of known networking principles (tunneling, L2 switching, hierarchical network design, and tunnel relaying) in light of the recognized scalability problems of existing overlay networks like VXLAN and NVGRE. A person having ordinary skill in the art would have been motivated to combine these elements to improve the expandability of virtual L2 networks.