Loop-Free Fabric via Distributed Address Port Tables
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Solution Overview
Problem
In data centers, layer-2 loops can occur due to misconfiguration or incorrect cabling, which are not detected by traditional Spanning Tree Protocol (STP) as virtual switches do not participate in STP, leading to network disruptions affecting tenants.
Innovation Solution
Implementing a network device operation system (ndOS) that shares a global switch table to detect loops, block affected ports, send loop-probe packets, and unblock ports when no loop-probe packets are received within a predetermined time, indicating the port is no longer part of the loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Spanning Tree Protocol (STP) is implemented to detect and correct loops, then network stability is improved, but virtual switches in hosts cannot participate in STP and loops created by hosts are not detected
Solution Approach 1:
The patent introduces loop-probe packets as an intermediary mechanism that enables loop detection in environments where traditional STP cannot be applied. These special packets circulate through the network and are tracked by the ndOS to detect loops created by virtual switches, effectively bridging the gap between STP capabilities and virtual switch participation requirements.
Solution Approach 2:
The patent replaces the traditional STP protocol mechanism with a novel loop-probe packet-based detection system. Instead of relying on STP's database synchronization and port state machine approaches, the system uses circulating probe packets with sequence numbers that can be tracked across virtual and physical network boundaries, substituting a more adaptable detection mechanism.
2Reliability
If ports are blocked to prevent loop-related packet flooding, then network stability is improved, but legitimate traffic through those ports is also blocked
Solution Approach 1:
The patent implements dynamic port blocking and unblocking based on real-time loop-probe packet reception status. Ports are blocked when loops are detected and unblocked when loop conditions are resolved, allowing the network to adapt its topology dynamically. This ensures that ports are blocked only when necessary, minimizing impact on legitimate traffic while maintaining network stability during loop conditions.
Solution Approach 2:
The system uses loop-probe packet reception as feedback to control port blocking decisions. When loop-probe packets are received indicating a loop condition, ports are blocked. When loop-probe packets are no longer received within a predetermined time, ports are unblocked. This feedback mechanism ensures that blocking actions are taken only when necessary and reversed when the loop condition is resolved.
3Measurement precision
If all ports are monitored for loop-probe packets to determine loop status, then loop detection accuracy is improved, but system complexity and processing overhead increase
Solution Approach 1:
The ndOS implements a universal loop-detection mechanism that operates across all network device types and port configurations through a common probe packet infrastructure. The same loop-probe packet mechanism works for physical ports, virtual ports, and ports on different network device types, eliminating the need for separate detection systems and reducing overall system complexity despite comprehensive monitoring.
Data Source
AI summary
Methods, systems, and computer programs are presented for managing a network in the presence of layer-2 loops. One method includes an operation for detecting, by a network device, a loop at a layer 2 of a network. The network device is configured to execute a network device operation system (ndOS), where network devices executing ndOS share a global switch table. The method further includes an operation for blocking ports associated with the loop where incoming packets received at the blocked ports are discarded except for loop-probe packets. Further, the method includes operations for sending loop-probe packets by one or more network devices executing ndOS through one or more ports, and for unblocking a first port of the blocked ports based on the loop-probe packets when a lack of receipt of a loop-probe packet within a predetermined amount of time is detected for the first blocked port which indicates that the first blocked port is not part of the loop.