Switch Buffer Congestion Control via Targeted Unicast Pause Frames
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Solution Overview
Problem
In High Performance Computing (HPC) networks, conventional packet relaying using Ethernet switches leads to inefficient transmission and communication service quality deterioration due to collective stopping of packet transmission across the network when congestion is detected, as all nodes receive multicast Pause packets, even if only a few are causing congestion.
Innovation Solution
A communication apparatus with a control unit that monitors packet reception frequency to detect congestion at a switch buffer and sends a transmission stop request only to the transmitter nodes causing congestion, preventing unnecessary packet transmission halts and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switch sends a multicast Pause packet to stop packet transmission when congestion is detected, then congestion at the switch buffer is prevented, but transmission efficiency deteriorates because all nodes stop transmitting packets even if they are not causing congestion
Solution Approach 1:
The patent segments the network flow control by implementing per-flow congestion control instead of network-wide control. The switch identifies individual transmitter nodes causing congestion and sends unicast pause frames only to those specific nodes, rather than using multicast pause packets that affect all nodes. This segmentation allows non-congested flows to continue transmitting while congested flows are controlled.
Solution Approach 2:
The patent applies local quality by making the pause frame transmission targeted and specific to individual congested flows. Instead of uniform network-wide pause transmission, the switch identifies the specific transmitter apparatuses causing congestion and sends pause frames only to them. This localized control preserves transmission efficiency for non-congested nodes while effectively preventing congestion at the switch buffer.
2Reliability
If all nodes stop transmitting packets when a multicast Pause packet is received, then switch buffer congestion is avoided, but communication service quality deteriorates due to unnecessary transmission halts
Solution Approach 1:
The patent segments the pause frame distribution by sending unicast pause frames only to specific transmitter nodes that are causing congestion, rather than using multicast frames that reach all nodes. This segmentation ensures that only the problematic flows are controlled, preserving communication service quality for other nodes while still avoiding buffer congestion.
Solution Approach 2:
The switch acts as an intermediary that intelligently identifies and targets the specific transmitter nodes causing congestion. Instead of blindly broadcasting pause frames to all nodes, the switch mediates by analyzing packet sources and directing control frames only where needed, thus maintaining service quality while preventing congestion.
3Productivity
If conventional flow control methods are used with high-performance switches, then network performance can be maintained, but device complexity and cost increase
Solution Approach 1:
The patent implements feedback mechanisms where the receiver node monitors packet reception and sends control frames back to the transmitter node when congestion is detected. This feedback loop allows the network to self-regulate flow without requiring complex switch hardware, maintaining network performance while reducing device complexity by distributing intelligence to the endpoints.
Solution Approach 2:
The patent enables endpoints (transmitter and receiver nodes) to perform flow control themselves through direct communication and control frame exchange. Instead of relying on the switch to perform complex flow control functions, the nodes themselves monitor and regulate their traffic, reducing the complexity requirements for switch hardware while maintaining network performance.
Data Source
AI summary
A first node and a second node transmit packets to a third node via a switch. The packets are buffered in a Tx buffer in the switch and then transmitted to the third node.When the third node detects a sign of congestion at the Tx buffer based on the reception frequency of the packets, it is recognized, from transmitter addresses included in the received packets, that the nodes transmitting the packets to the third node are the first node and the second node, and a control packet for a transmission stop request is transmitted to the first node and the second node. On receiving the control packet for a transmission stop request, the first node stops transmission of only packets addressed to the third node. On receiving the control packet for a transmission stop request, the second node stops transmission of only packets addressed to the third node.