Selective Flow Control for Ethernet Congestion
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Solution Overview
Problem
Conventional Ethernet networks lack effective control mechanisms to handle bursty traffic, leading to packet loss, delay, and unfavorable impacts on service contracts due to limited buffering and unnecessary PAUSE message transmissions.
Innovation Solution
Implementing a selective flow control procedure that identifies and transmits flow control messages only to upstream devices operating above a guaranteed service rate, using a network device with a flow control unit, link monitoring unit, and control policies to manage congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If buffering is used to hold excessive traffic during congestion, then traffic bursts can be accommodated, but packet loss occurs when buffers overflow and delay increases
Solution Approach 1:
The system implements feedback by monitoring traffic rates and buffer status, then dynamically adjusting flow control decisions. The flow control unit receives feedback about traffic exceeding guaranteed rates and responds by sending PAUSE messages to upstream devices, creating a closed-loop control system that prevents buffer overflow while maintaining service contracts.
Solution Approach 2:
The system changes the parameter of flow control application by transitioning from universal flow control to selective flow control based on service contracts. It modifies the behavior of PAUSE message transmission by considering the guaranteed service rate parameter, only applying flow control to devices exceeding their contracted rates rather than all upstream devices.
2Ease of operation
If PAUSE messages are transmitted to all upstream devices during congestion, then traffic flow can be controlled, but devices operating within guaranteed service rates are unnecessarily restricted
Solution Approach 1:
The system applies local quality by differentiating treatment based on the local condition of each upstream device relative to its service contract. Instead of uniform flow control, it selectively applies PAUSE messages only to devices whose traffic exceeds their guaranteed service rate, preserving quality of service for compliant devices while controlling congestion from excessive traffic.
Solution Approach 2:
The system segments upstream devices into two categories: those exceeding their guaranteed service rate and those within their contracted rates. This segmentation allows differential flow control application, where PAUSE messages are transmitted only to the first group, preventing unnecessary restriction of services for compliant devices.
3Ease of operation
If conventional flow control is applied to all upstream devices, then congestion can be managed, but delay and delay variation increase degrading service quality
Solution Approach 1:
The system changes the parameter of flow control selectivity by introducing service contract awareness into the congestion management process. It modifies the congestion response by evaluating traffic rate parameters against guaranteed service rates, applying flow control only when necessary to prevent buffer overflow from excessive traffic, thereby minimizing unnecessary delay for compliant flows.
Data Source
AI summary
A network device controls the flow of traffic in a network, such as an Ethernet-based network. The network device detects congestion in the network and identifies at least one upstream device to which to send a flow control message, where the upstream device is a device that is transmitting above a predetermined level. The network device then transmits the flow control message to the identified upstream device. The flow control message instructs the identified upstream device to slow down transmissions to the network device.