Obviousness

Obviousness Analysis of US Patent 8,018,880 under 35 U.S.C. § 103

This analysis assesses the obviousness of US patent 8,018,880 based on the provided prior art, from the perspective of a Person Having Ordinary Skill in the Art (PHOSITA) at the time of the invention (priority date March 26, 2007). A PHOSITA in this field would likely possess a Bachelor's or Master's degree in Electrical Engineering, Computer Science, or a related field, along with several years of experience (e.g., 3-5+ years) in designing, implementing, or operating carrier-grade Ethernet networks, MPLS networks, or enterprise networking solutions. Such a person would be familiar with relevant IEEE standards (e.g., 802.1ah for PBB, 802.1Qay for PBB-TE/PBT) and IETF RFCs (e.g., RFC 4761, 4762 for VPLS), network management protocols (e.g., SNMP, CLI), and fundamental bridging concepts including MAC address learning and loop prevention mechanisms like Spanning Tree Protocol (STP) and split horizon.

The patent US8018880B2 introduces methods, systems, and computer program products for creating Layer 2 Virtual Private Networks (L2VPNs) over Provider Backbone Bridge (PBB) networks using Provider Backbone Transport (PBT) or PBB Traffic Engineering (PBB-TE) trunks. Key aspects include provisioning Virtual Switch Instances (VSIs) via an external control plane and employing novel split horizon rules for: (1) interworking between PBB and Multi Protocol Label Switching (MPLS) networks (specifically VPLS), and (2) interworking between PBB core and PBB metro networks.

Argument 1: Obviousness of PBB-MPLS (VPLS) Interworking with External Control Plane and Adapted Split Horizon Rules (Claims 1, 14, 26)

Differences from Prior Art:
Claims 1, 14, and 26 describe an L2VPN over a PBB network using PBT/PBB-TE trunks, with VSIs provisioned by an external control plane. The most distinct feature is the application of specific split horizon rules at a VSI coupling the PBB network to an MPLS network (VPLS). These rules dictate frame forwarding based on the ingress interface type (Service Instance over PBT, Pseudowire over MPLS, or customer bound interface) to prevent loops.

Motivation for Combination and Obviousness:
A PHOSITA, at the time of the invention, would have been motivated to combine known networking technologies and techniques to achieve scalable and robust L2VPN services.

1. Interworking of Heterogeneous L2VPNs: The problem of interconnecting different Layer 2 VPN technologies, such as Ethernet networks and MPLS-based VPLS, was well-known. For instance, US20050044262A1 (Cisco Technology, Inc.) teaches a "system and method for interconnecting heterogeneous Layer 2 VPN applications," directly addressing the general problem of interworking. Similarly, US20080172497A1 (Nortel Networks Limited) describes a "method and apparatus for interworking Ethernet and MPLS networks." More specifically, US20080212595A1 (Hammerhead Systems, Inc.) explicitly describes "mapping PBT and PBB-TE traffic to VPLS and other services," demonstrating a direct teaching to combine these specific technologies. Given these teachings, it would have been obvious for a PHOSITA to combine PBB/PBT L2VPNs with VPLS L2VPNs to provide broader connectivity. The use of Virtual Switch Instances (VSIs), which are recognized as standard learning bridges (IEEE 802.1D and 802.1Q) and are fundamental to VPLS (IETF RFC 4762 and RFC 4761), at the interworking point would be a predictable architectural choice for bridging traffic between these two network types.

2. External Control Plane Provisioning: The use of an external control plane for provisioning network elements was also a known and desirable approach for managing network complexity and achieving scalability. US20080219268A1 (Dennison Larry R.) describes a "software control plane for switches and routers" and highlights its advantages in decoupling control logic from hardware for improved scalability and innovation. The '880 patent itself details similar benefits of an external control plane. A PHOSITA would have been motivated to apply such an external control plane to automate the provisioning of VSIs and PBT trunks in a combined PBB-VPLS environment, leveraging its known benefits for large-scale deployments.

3. Adapted Split Horizon Rules for Loop Prevention: The fundamental problem of forwarding loops in interconnected bridged networks is well-understood, and "split horizon" is a known technique to prevent such loops in L2VPNs. The '880 patent explicitly acknowledges this by stating, "A form of split horizon is also used with VPLS, as described in RFC 4762." [cite: Current time information in United States of America.] RFC 4762's split horizon rule (rule 511 in FIG. 5 of '880 patent) prevents frames from being forwarded back to another Pseudowire, thereby avoiding loops within a VPLS network.
   A PHOSITA, combining a PBB network with a VPLS network via a VSI, would immediately recognize the potential for forwarding loops at this interworking point. Motivated by the known need for loop prevention in such scenarios and the existing use of split horizon in VPLS, they would predictably adapt the split horizon principle. The claimed rules (1) "in the event a frame is received from a Service Instance over one of the plurality of provider backbone trunks, the received frame is forwarded to Pseudowires over the MPLS network and a set of customer bound interfaces" and (2) "in the event a frame is received from a Pseudowire over the MPLS network, the received frame is forwarded to a set of Service Instances over the plurality of provider backbone trunks and a set of customer bound interfaces" are direct and logical extensions of the split horizon principle. These rules prevent frames from re-entering their originating network segment (PBB frames from going back to PBB, MPLS frames from going back to MPLS) through the interworking VSI, while allowing forwarding to the other network segment and local customer interfaces. Rule (3), allowing normal VSI forwarding for frames from customer interfaces, is standard bridge behavior to reach all parts of the L2VPN. This adaptation of a known loop prevention technique to a new but analogous interworking context would be obvious to a PHOSITA.

Therefore, the combination of the teachings from US20050044262A1 (interconnecting heterogeneous L2VPNs), US20080212595A1 (mapping PBT/PBB-TE to VPLS), the established VPLS split horizon principle (RFC 4762 as acknowledged in '880), and US20080219268A1 (external control plane), would render the methods, systems, and computer program products of claims 1, 14, and 26 obvious.

Argument 2: Obviousness of PBB Core-Metro Interworking with External Control Plane and Adapted Split Horizon Rules (Claim 39)

Differences from Prior Art:
Claim 39 describes a method for interconnecting a PBB core network with a PBB metro network using a VSI. The key distinguishing feature is the application of specific split horizon rules at this interworking VSI to manage frame distribution between the core and metro segments and customer interfaces.

Motivation for Combination and Obviousness:

1. Hierarchical PBB Network Architectures: The concept of segmenting a large L2 network into hierarchical components, such as metro and core networks, is a known scaling practice in telecommunications and Ethernet networks. The patent itself implies this by describing an "end-to-end L2VPN over PBB for a customer using a PBB Core network and two PBB metro networks" (FIG. 6) and stating that "one or multiple PBB metro networks can be connected to a PBB core network." This indicates that such hierarchical PBB deployments were either existing or a natural evolution. US20040081171A1 (Finn Norman W.) describes a "large-scale Layer 2 metropolitan area network," broadly suggesting the context of large, segmented L2 networks. A PHOSITA would recognize the benefits of such segmentation for scalability and management in a PBB environment. Interconnecting these segments using VSIs, which function as learning bridges, would be a conventional approach for bridging traffic.

2. External Control Plane Provisioning: As discussed for Argument 1, the provisioning of VSIs and PBT trunks via an external control plane, as claimed in claim 39, would be obvious in light of US20080219268A1 (Dennison Larry R.), which promotes the use of such control planes for flexible and scalable network management.

3. Adapted Split Horizon Rules for Loop Prevention in PBB Core-Metro: When interconnecting two bridged PBB domains (core and metro) via a VSI, a PHOSITA would readily identify the potential for forwarding loops, similar to the interworking scenario with VPLS or any interconnected bridged network. Given the established knowledge of split horizon as a loop prevention mechanism in L2VPNs (e.g., in VPLS as per RFC 4762 and acknowledged by '880), a PHOSITA would be motivated to adapt this technique for the PBB core-metro interworking VSI.
   The claimed split horizon rules for this scenario (rule 601 in FIG. 6 of '880 patent) state: (1) "whenever a frame is received from one of a second set of Service Instances over the second plurality of provider backbone trunks of the PBB metro network, the received frame can only be forwarded to the first set of Service Instances over the first plurality of provider backbone trunks of the PBB core network and a set of customer bound interfaces;" and (2) "whenever a frame is received from one of a first set of Service Instances over the first plurality of provider backbone trunks of the PBB core network, the received frame can only be forwarded to the second set of Service Instances over the second plurality of provider backbone trunks of the PBB metro network and a set of customer bound interfaces." These rules are a direct application of the core split horizon principle: a frame arriving from a specific segment (metro or core) is prevented from being forwarded back into the same segment through the interworking VSI, while being allowed to proceed to the other segment and local customer interfaces. Rule (3), allowing normal VSI forwarding for frames from customer interfaces, is standard bridge behavior. This adaptation of a known and effective loop prevention method to a new but analogous interworking point, addressing a predictable problem, would be obvious to a PHOSITA.

Therefore, the combination of the known architectural practice of hierarchical L2 networks (as generally understood and implied by the patent figures), the standard use of VSIs as learning bridges, the well-known principles of split horizon for loop prevention in L2VPNs (RFC 4762 as acknowledged in '880), and the teachings of US20080219268A1 (external control plane), would render the method of claim 39 obvious.