IGMP Snooping Switch Multicast Recovery STP Topology Change
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Solution Overview
Problem
In Layer 2 networks, there is no existing method to expedite the recovery of multicast router ports after a spanning tree protocol (STP) topology change, leading to prolonged multicast traffic loss and significant information loss.
Innovation Solution
The introduction of a General Query Solicit (GQS) message, which is flooded by IGMP snooping switches on all forwarding ports to solicit a general query from a multicast snooping querier, enabling the rebuilding of the multicast traffic routing tree by sending a general query message on a virtual local area network (VLAN).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If traditional IGMP query mechanisms are used after STP topology change, then the network maintains protocol simplicity, but multicast traffic recovery takes multiple minutes causing significant information loss
Solution Approach 1:
The patent applies preliminary action by having the multicast router proactively send a General Query Solicit (GQS) message immediately upon detecting STP topology change, before the standard IGMP query mechanism would naturally trigger. This proactive approach initiates the multicast traffic recovery process earlier, reducing both the recovery time and information loss by preemptively seeking group membership information from hosts after the topology change.
2Reliability
If IGMP general queries with source=0.0.0.0 are sent to recover multicast traffic, then some traffic recovery is achieved, but the solution is incomplete and leaves another problem to be solved
Solution Approach 1:
The patent introduces an intermediary mechanism by defining a new GQS message type that acts as a mediator between the multicast router and hosts. This GQS message specifically solicits group membership information in a standardized manner, completing the recovery process that was left incomplete by simply sending IGMP general queries with source=0.0.0.0. The intermediary GQS message bridges the gap between topology change detection and full multicast traffic recovery.
3Productivity
If IGMP query interval is lowered to 15 seconds to speed up recovery, then multicast traffic recovers faster, but the solution is not scalable and ineffective in large scale distributed network systems
Solution Approach 1:
The patent applies segmentation by dividing the multicast recovery process into distinct phases: immediate GQS message transmission upon STP topology change detection, followed by targeted group membership information collection. This segmented approach allows fast recovery without continuously lowering the IGMP query interval throughout the network, making the solution scalable to large distributed networks while maintaining high productivity in recovery scenarios.
Data Source
AI summary
In one embodiment, an apparatus includes a processing circuit and logic integrated with and/or executable by the processing circuit. The logic is configured to cause the processing circuit to handle Internet Group Membership Protocol (IGMP) messages received from other devices in a network. Also, the logic is configured to cause the processing circuit to create a general query solicit (GQS) message configured to solicit a general query (GQ) from a multicast snooping querier coupled with the apparatus. In another embodiment, a method includes handling, using a switch in a network, IGMP messages received from other devices in the network, and creating, using the switch, a GQS message configured to solicit a GQ from a multicast snooping querier coupled with the switch. Other systems, methods, and computer program products are described in more embodiments.