VPLS Flush Mechanism for BGP-Based Networks
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Solution Overview
Problem
In VPLS networks, topology changes that do not result in pseudowire teardown can lead to stale MAC addresses, causing delays in connectivity restoration due to the lack of explicit notification mechanisms for flushing MAC addresses, which are typically deleted only when age-out timers expire, taking minutes to converge.
Innovation Solution
A new BGP Capability is introduced, enabling the use of a VPLS-FLUSH message to explicitly notify remote PE routers to flush MAC addresses, thereby expediting the process and reducing the need for a new protocol, utilizing Route Targets for efficient message propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MAC addresses are deleted only when age-out timers expire, then network stability is maintained, but connectivity restoration time increases significantly
Solution Approach 1:
The patent applies preliminary action by introducing a proactive MAC address flush mechanism that triggers before the age-out timer expires. When a pseudowire is torn down or topology changes occur, the system immediately sends flush notifications to PE routers to delete stale MAC addresses upfront, rather than waiting for the timer to expire naturally. This preliminary flushing action significantly reduces connectivity restoration time while maintaining network stability through controlled, notification-based flushes.
2Loss of time
If a new protocol is deployed for MAC address flush notification, then connectivity restoration is expedited, but device complexity increases
Solution Approach 1:
The patent applies universality by making BGP capable of serving multiple functions: traditional routing plus the new MAC address flush notification mechanism. Instead of deploying a separate dedicated protocol for flush notifications, the system extends BGP to carry both routing information and flush commands through a unified protocol framework. This multi-functionality approach expedites connectivity restoration without proportionally increasing device complexity, as PE routers already run BGP and only need to add flush handling capability.
Data Source
AI summary
A network device includes a control unit configured to execute an extended layer three (L3) routing protocol within a control plane of the network device. The extended L3 routing protocol is extended to process a routing protocol control message having a set of layer two (L2) identifiers of customer devices attached to an autonomous system (AS) and an indicator that specifies a Route Target associated with a Virtual Private Local Area Network Service (VPLS) domain within the AS. The routing protocol control message conforms to a message type of the L3 routing protocol to initiate a flush of the set of L2 identifiers.