VPLS Multi-Homing Active-Active Topology via MAC Segmentation
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Solution Overview
Problem
Traditional multi-homed network deployments using an 'active-standby' link topology are wasteful of resources and prone to issues like packet duplicates, MAC moves, and loops, as only a single link is used for network traffic at any given time.
Innovation Solution
Implementing an 'active-active' link topology in multi-homed networks by distributing the multi-homed VPLS site MAC address space among all PE routers, allowing each router to handle traffic associated with a specific portion of the address space, thereby avoiding packet duplicates, MAC moves, and loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an 'active-standby' link topology is used in multi-homed networks, then network stability is improved by avoiding packet duplicates, MAC moves, and loops, but network resource utilization deteriorates because only a single link is used for network traffic at any given time
Solution Approach 1:
The invention segments the MAC address space into different portions and assigns each portion to a specific PE router. This allows multiple PE routers to simultaneously handle traffic for different segments of the customer network, enabling active-active operation while avoiding the packet duplication and MAC move issues that would occur if all routers handled all MAC addresses. The segmentation resolves the contradiction by allowing resource utilization to improve while maintaining stability through structured address space division.
Solution Approach 2:
The invention applies local quality by making each PE router specialize in handling traffic for specific portions of the MAC address space rather than all traffic. Each router develops local expertise and responsibility for its assigned MAC address portions, allowing concurrent active operation. This specialization enables multiple routers to be active simultaneously without causing the stability issues that would arise from universal traffic handling.
2Productivity
If an 'active-active' link topology is implemented by allowing all PE routers to handle all traffic, then network resource utilization is improved by enabling concurrent active operation, but network stability deteriorates due to packet duplicates, MAC moves, and loops
Solution Approach 1:
The MAC address space is segmented into distinct portions, with each PE router responsible for specific segments. This segmentation prevents packet duplicates because each router only forwards packets for its assigned MAC address portions. It prevents MAC moves because MAC address-to-router mappings are statically defined through the segmentation scheme. It prevents loops because the segmented approach creates a deterministic forwarding path for each MAC address, eliminating the ambiguity that causes loops in fully active-active configurations.
Solution Approach 2:
Instead of having each PE router handle all MAC addresses (the conventional approach), the invention inverts the approach by having each PE router handle only specific portions of the MAC address space. This inversion allows active-active operation while maintaining stability, as the inverted assignment scheme creates clear boundaries that prevent the stability issues inherent in universal traffic handling.
3Productivity
If the MAC address space is distributed among multiple PE routers, then device complexity increases due to the need for address space management and packet inspection, but this enables active-active operation that improves network resource utilization
Solution Approach 1:
The invention applies preliminary action by pre-distributing the MAC address space among PE routers before operation begins. This pre-assignment creates a static mapping between MAC address portions and specific routers, eliminating the need for dynamic address space management during operation. Each router inspects only the MAC address portion it is responsible for, significantly reducing inspection complexity. The preliminary distribution resolves the contradiction by establishing order before the complex active-active operation begins.
Solution Approach 2:
The invention changes the parameter of MAC address handling from a universal approach (all routers handle all addresses) to a segmented approach (each router handles specific address portions). This parameter change transforms the complexity from dynamic address space management to static, pre-defined address portion assignment. The parameter change enables active-active operation while reducing operational complexity through the structured distribution scheme.
Data Source
AI summary
Techniques are described for forwarding packets in a VPLS using multi-homing PE routers configured in an “active-active” link topology. As described herein, a PE router receives a packet from a multi-homed VPLS customer site, and processes the packet to determine a portion of a MAC domain to which the packet corresponds. When the packet is determined to correspond to a portion associated with the PE router, the PE router forwards the packet to the destination in accordance with forwarding protocols executing on the PE router. When the packet is determined to correspond to a portion associated with a second PE router, the PE router forwards the packet to the second PE router via a pseudowire that is external to the VPLS domain, and the second PE router forwards the packet to the destination in accordance with forwarding protocols executing on the second PE router.