Stacked Switch Packet Forwarding via Source Information
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Solution Overview
Problem
Existing stacked switch systems face challenges in efficiently forwarding multicast, broadcast, and unknown unicast packets across multiple stack groups without causing forwarding loops or storms, particularly in ring and chain topologies, due to the complexity of managing stack ports and aggregated link groups.
Innovation Solution
The method involves assigning exclusive IDs to each switch and using these IDs to determine permitted forwarding paths, avoiding loops by configuring source forwarding information that specifies which stack ports and aggregated link groups are forbidden for packet forwarding, ensuring packets are sent through the shortest paths and preventing redundant forwarding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If packets are flooded to all switches in stacked switch systems, then all switches receive intended packets, but forwarding loops and storms occur
Solution Approach 1:
The patent segments the stacked switch system into multiple stack groups, where each switch maintains source forwarding information specific to its stack group. This segmentation allows packets to be flooded within groups while preventing cross-group loops, resolving the contradiction between reliable packet delivery and avoiding forwarding storms.
Solution Approach 2:
The patent implements preliminary action by pre-configuring source forwarding information in each switch before packet forwarding occurs. This information includes stack group identifiers and forbidden stack port identifiers, enabling switches to make immediate forwarding decisions without creating loops, thus ensuring reliable delivery while preventing storms.
2Reliability
If source forwarding information is configured for each switch, then forwarding loops are avoided, but system complexity increases
Solution Approach 1:
The patent applies universality by creating a standardized source forwarding information structure that serves multiple functions: identifying stack groups, determining forbidden ports, and enabling rapid forwarding decisions. This multi-functional approach reduces overall system complexity while maintaining loop-free forwarding.
Solution Approach 2:
The patent changes key parameters by introducing stack group identifiers and forbidden stack port identifiers as standardized fields in source forwarding information. These parameter changes enable automated configuration and simplified management, reducing the complexity burden while ensuring reliable loop-free forwarding.
3Reliability
If packets are sent through multiple paths for redundancy, then network reliability improves, but forwarding loops occur
Solution Approach 1:
The patent applies preliminary anti-action by pre-identifying and marking forbidden stack ports in the source forwarding information before packet transmission. This prevents packets from being forwarded through paths that would create loops, while still allowing redundant paths within safe boundaries, thus maintaining network reliability without creating forwarding loops.
Data Source
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Figure 3A
AI summary
A member device of a stacked switches system receives a packet which is to be sent to every member device in the stack groups of the stacked switches system. The member device identifies an intra-group port and an aggregated stack link group which permit forwarding the packet based on an ingress member device identification of the packet. The member device sends the packet carrying the ingress member device identification via the identified intra-group stack port, via the identified aggregated stack link group and via a local data port.