PE Switch DF Configuration for SPB over VPLS
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Solution Overview
Problem
Current Virtual Private LAN Service (VPLS) implementations do not support multiple unblocked attachment circuits for Shortest Path Bridging (SPB), limiting the use of SPB features and lacking symmetric and congruent multicast trees, which are essential for efficient network utilization and reliability.
Innovation Solution
The method involves a provider edge (PE) switch that receives IS-IS protocol data units to determine if the Designated Forwarder (DF) configuration needs to be changed, updating the DF status and associated information in pseudowire and IS-IS databases to support Shortest Path Bridging MAC Mode (SPBM) over a VPLS network, ensuring seamless communication and interworking with existing standards like 802.1ah and 802.1Qbp.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VPLS is implemented without multiple unblocked attachment circuits, then the network configuration is simpler, but SPB features cannot be fully utilized and network reliability is reduced
Solution Approach 1:
The patent segments the VPLS network into multiple attachment circuits with distinct DF roles. Each attachment circuit can be independently configured with its own DF, enabling multiple unblocked paths while maintaining manageable configuration through structured separation of functions.
Solution Approach 2:
The patent implements dynamic DF election and re-election mechanisms that automatically adapt to network topology changes. The DF status can change dynamically based on link state updates, allowing the network to maintain optimal paths without manual reconfiguration, thus improving reliability while managing complexity through automation.
2Productivity
If symmetric and congruent multicast trees are not implemented, then the network structure is simpler, but bandwidth utilization is reduced and network mesh topology cannot be fully exploited
Solution Approach 1:
The patent introduces asymmetric DF configurations where different attachment circuits can have different DF assignments. This allows the network to exploit mesh topology by creating asymmetric paths for different traffic types while maintaining overall structural simplicity through standardized DF election rules.
Solution Approach 2:
The patent makes the DF mechanism universal by enabling any attachment circuit to serve as a DF for specific B-VIDs. This multi-functional capability allows the same network infrastructure to support multiple multicast tree configurations simultaneously, improving bandwidth utilization without requiring separate dedicated structures for each function.
3Speed
If multiple equal cost paths are not supported, then the routing configuration is simpler, but network mesh topology utilization is limited and convergence time increases
Solution Approach 1:
The patent implements feedback mechanisms through IS-IS protocol updates that continuously monitor link states and trigger DF re-election when topology changes occur. This feedback-driven approach enables rapid convergence by automatically detecting and responding to network changes, reducing convergence time while managing configuration complexity through standardized protocol responses.
Solution Approach 2:
The patent utilizes parameter changes in the IS-IS protocol (such as system ID comparisons and cost values) to dynamically determine DF status. By changing these parameters in response to topology changes, the network can quickly reconfigure paths without complex manual routing adjustments, achieving fast convergence with manageable configuration complexity.
Data Source
AI summary
Methods and devices for implementing Shortest Path Bridging over a VPLS network. The method includes determining, from IS-IS PDU information received by a PE switch, whether a DF configuration for the PE switch needs to be changed and, if so, the method further includes determining whether the PE switch remains a DF for one or more B-VIDs. If the PE switch is no longer a DF for one or more B-VIDs, the method further includes removing local DF associated information for the PE switch from each PW adjacency's LDP database, and removing, from a local IS-IS database, DF associated remote LDP information. The method also includes, if the PE switch has become a DF for one or more of the B-VIDs, adding, from the IS-IS database, local DF information for the PE switch to the LDP databases, and adding, from the LDB databases, DF associated remote information for the PE switch to the IS-IS database.