Intra-Packet Flow Control for Asymmetric Communication Links

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Solution Overview

Problem

Existing flow control mechanisms in data communication networks require large receive buffers due to delayed transmission of flow-control messages, which increases latency, size, cost, and power consumption, especially in asymmetric links with smaller bandwidth in one direction.

Innovation Solution

Temporarily suspending packet transmission to allow immediate flow-control message transmission, using suspension and resumption markers, and reassembling packets at the receiving end to reduce latency and buffer size without degrading bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If flow-control messages are sent immediately when needed, then latency is reduced, but packet transmission continuity is disrupted

Engineering Contradiction:

ImprovelatencyVSAvoidpacket transmission continuity

Core Design Contradiction:

Loss of timeVSProductivity

Solution Approach 1:

The data packet transmission is segmented into portions, allowing the transmitter to pause after sending a first portion, send a flow-control message, then resume and send a second portion. This segmentation enables timely flow-control communication while maintaining overall transmission progress.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transmitter sends a portion of the data packet before the flow-control message is needed, prepares to send the flow-control message at the appropriate pause point, and then resumes transmission. This preliminary action of sending data portions beforehand allows for timely flow-control communication without excessive latency.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If large receive buffers are used to accommodate delayed flow-control messages, then bandwidth efficiency is maintained, but device size and power consumption increase

Engineering Contradiction:

Improvebandwidth efficiencyVSAvoidbuffer size

Core Design Contradiction:

ProductivityVSWeight of stationary object

Solution Approach 1:

The receive buffer size is made dynamic rather than statically large. By sending flow-control messages timely during packet transmission, the receiver can regulate data flow dynamically, allowing the buffer to be smaller while still maintaining bandwidth efficiency through active flow control management.

Inventive Principle:

Principle #15Dynamics

3Reliability

If packet transmission is suspended to send flow-control messages, then flow control accuracy is improved, but transmission speed decreases

Engineering Contradiction:

Improveflow control accuracyVSAvoidtransmission speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

Instead of suspending the entire packet transmission, only a portion is sent before the flow-control message, and then the transmission is resumed. This partial action approach maintains flow control accuracy while minimizing the impact on overall transmission speed by avoiding complete suspension.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS8908510B2Communication link with intra-packet flow control

Publication Date: 2014.12.09 MELLANOX TECH TLV

AI summary

A method for communication includes transmitting a data packet from a first port to a second port over a communication link. After transmission of a first portion of the data packet, the transmission is temporarily suspended, a flow-control message is sent from the first port to the second port over the communication link while the transmission is temporarily suspended, and then the transmission is resumed so as to transmit a second portion of the data packet.