Credited Network Buffer Reallocation Without Frame Drops

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Solution Overview

Problem

Existing credit-based networks, such as Fibre Channel and InfiniBand, require port flaps to adjust buffer credits, leading to undesirable frame drops and downtime, especially when reallocating buffers across ports or virtual lanes for congestion relief or capacity adjustments.

Innovation Solution

Implement a non-disruptive buffer credit reallocation method using receive and transmit credit hold features, enabling intelligent buffer movement between ports or virtual lanes without frame drops, utilizing a two-stage handshake protocol and internal messaging to synchronize credit counters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If buffer credits are reallocated by bringing links down and reallocating during link up, then buffer credits can be adjusted, but frame drops and downtime occur

Engineering Contradiction:

Improvebuffer credit adjustmentVSAvoidframe loss

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent enables dynamic buffer credit reallocation during operational links by introducing receive credit hold and transmit credit hold mechanisms. These allow buffers to be moved between ports or virtual lanes without shutting down links, transforming a static allocation system into a dynamic one that can adapt to changing conditions while maintaining continuous data transmission.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses credit hold mechanisms as intermediaries to facilitate buffer movement. The receive credit hold feature holds received credits temporarily, while the transmit credit hold feature holds transmitted credits, allowing buffer credits to be reallocated without immediately affecting active data transmission. This intermediary approach enables smooth buffer migration without frame drops.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If buffer credits are reallocated by bringing links down, then buffer credits can be adjusted, but downtime occurs

Engineering Contradiction:

Improvebuffer credit adjustmentVSAvoiddowntime

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent transforms the buffer allocation system from static to dynamic by enabling reallocation during operational links. The receive and transmit credit hold features allow buffers to be moved between ports or virtual lanes without interrupting data transmission, eliminating downtime while maintaining adaptability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent ensures continuous data transmission during buffer reallocation by using credit hold mechanisms. The receive credit hold prevents immediate release of received credits, while transmit credit hold prevents immediate transmission of held credits, maintaining continuous flow of data buffers during the reallocation process without interruption.

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If buffer credits are reallocated during operational links, then frame loss is prevented, but credit flow disruption may occur

Engineering Contradiction:

Improveframe loss preventionVSAvoidcredit flow stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent implements feedback mechanisms through the receive and transmit credit hold features. The system continuously monitors credit availability and usage patterns, using this feedback to dynamically adjust buffer allocations. The receive credit hold responds to received buffer credits by holding them temporarily for reallocation, while transmit credit hold responds to transmission needs, maintaining stable credit flow while preventing frame loss.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The credit hold mechanisms act as intermediaries that buffer and regulate credit flow during reallocation. The receive credit hold mediates between received credits and their allocation, while the transmit credit hold mediates between available credits and transmission needs, ensuring smooth credit flow transitions without disruption during buffer movement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12375431B2Non-disruptive trading of buffers between ports or port virtual lanes of a credited network

Publication Date: 2025.07.29 CISCO TECHNOLOGY INC

AI summary

Techniques for moving buffers between ports, or virtual lanes of a port, of a networking device of a credited network while maintaining the ports in an active state without dropping any frames. The techniques may include determining that a number of buffers are to be reallocated from a first port of a networking device to a second port of the networking device. The techniques may also include causing a peer port connected to the first port to decrement, by the number, a transmit credit counter associated with the peer port. Based at least in part on determining that the peer port decremented the transmit credit counter, the first port may release the number of the buffers from a buffer pool associated with the first port, and the number of the buffers may be reallocated to the second port.