Network Flow Control State Machines for Latency Reduction

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Solution Overview

Problem

Network devices such as switches and routers face significant delays in servicing flow control requests, leading to increased complexity, cost, and decreased performance due to large round trip latency in communicating flow control information.

Innovation Solution

Implementing a dedicated control path and state machines to accelerate the processing of flow control messages, along with enhanced buffer and block management in transmit buffers, to reduce the time interval for servicing flow control requests.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If traditional flow control messaging is used, then flow control can be implemented, but significant delay occurs between issuing and servicing flow control requests

Engineering Contradiction:

Improveflow control request delayVSAvoidflow control servicing speed

Core Design Contradiction:

Loss of timeVSProductivity

Solution Approach 1:

The patent segments the flow control processing into separate state machines (ingress flow control state machine and egress flow control state machine) located at different points in the data path. This segmentation allows parallel processing of flow control messages alongside data packets, eliminating the sequential delay where flow control requests had to wait for data processing to complete.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The ingress flow control state machine preliminarily processes flow control messages as they arrive, generating appropriate responses before the egress side needs them. This preliminary action at the ingress point allows the system to prepare flow control responses in advance, reducing the overall latency when servicing flow control requests at the egress point.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If large buffer spaces are allocated to accommodate flow control delays, then flow control can be maintained, but device complexity and cost increase

Engineering Contradiction:

Improveflow control reliabilityVSAvoidbuffer management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The flow control state machines automatically manage their own operation, transitioning between states based on received messages without requiring complex external buffer management. The ingress state machine self-manages receiving flow control messages and generating responses, while the egress state machine self-manages servicing these requests, eliminating the need for large centralized buffers and complex buffer management logic.

Inventive Principle:

Principle #25Self-service

3Ease of operation

If flow control processing is integrated with data path processing, then unified management is achieved, but flow control request servicing delay increases

Engineering Contradiction:

Improveflow control management unityVSAvoidflow control processing time

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent segments flow control processing into dedicated state machines that are functionally integrated with the data path but operationally independent. The ingress flow control state machine handles message reception and response generation, while the egress flow control state machine handles message servicing, allowing parallel processing that maintains unity of purpose while eliminating processing delays.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS7554908B2Techniques to manage flow control

Publication Date: 2009.06.30 INTEL CORP

AI summary

Method and apparatus to manage flow control for a network device are described.