Multi-Chassis Link Aggregation Source Identification
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Solution Overview
Problem
Conventional multi-chassis link aggregation groups (MC-LAGs) are limited to two chassis due to the inability to determine the source chassis of a packet, leading to potential network loops when trying to expand to three or more chassis.
Innovation Solution
Incorporating a SourceID into Ethernet tags of packets to identify the source chassis, allowing network devices to determine the origin and prevent loops by adding data that identifies the source chassis when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional MC-LAG techniques are used with two chassis, then packet source determination is straightforward, but expanding to three or more chassis becomes impossible due to inability to determine source chassis
Solution Approach 1:
The patent introduces an intermediary mechanism (source chassis identification data) that mediates between multiple chassis in the MC-LAG. This identifier acts as a mediator that allows any chassis to determine the original source of a packet regardless of how many hops or intermediate chassis the packet has traversed, thus enabling expansion beyond two chassis while maintaining manageable complexity.
Solution Approach 2:
The patent adds a new dimension to packet metadata by incorporating source chassis identification data into Ethernet tags. This additional dimensional information (source identifier) transforms the problem from a geometric/topological challenge (determining source in multi-chassis topology) into a simple data lookup problem, enabling scalability to three or more chassis.
2Loss of information
If source chassis identification data is added to Ethernet tags, then packet source can be determined in multi-chassis MC-LAG, but Ethernet tag structure becomes more complex
Solution Approach 1:
The patent makes the Ethernet tag structure universal by designing it to accommodate multiple functions: traditional VLAN identification, priority marking, and now source chassis identification. This multi-functional tag structure avoids creating entirely new complex protocols while extending existing Ethernet tag capabilities to handle source identification in multi-chassis environments.
3Reliability
If MC-LAG is limited to two chassis, then source determination is simple, but network redundancy and bandwidth are constrained
Solution Approach 1:
The patent segments the source determination function from the chassis topology structure. Instead of relying on the simple two-chassis topology to imply source identification, the solution segments the identification data into a separate field within the Ethernet tag. This allows the determination logic to remain simple (lookup the source identifier) while the topology can scale to any number of chassis for enhanced redundancy.
Data Source
AI summary
In one example, a network device comprising a first chassis of a multi-chassis link aggregation group (MC-LAG) having three or more chassis, comprises one or more network interfaces configured to receive a packet to be forwarded using the MC-LAG, and a control unit configured to determine whether the packet was received from a device outside of the MC-LAG, when the packet was received from the device outside of the MC-LAG, add data to the packet that identifies the first chassis as a source of the packet for the MC-LAG, and forward the packet via at least one of the network interfaces. In this manner, chassis of the MC-LAG can prevent forwarding of the packet to the source of the packet for the MC-LAG, based on the data that identifies a source of the packet for the MC-LAG.