PHY Pause Frames for MACsec Buffer Overflow Prevention

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Solution Overview

Problem

The IEEE 802.1AE MACsec standard introduces challenges due to packet enlargement during encryption, leading to increased transmission time and buffer overflow issues, as there is no effective way to adjust transmission rates or provide out-of-band signals to manage these changes.

Innovation Solution

A system and method where the physical layer (PHY) generates pause frames to notify the medium access controller (MAC) to pause and resume packet transmissions, utilizing in-band notifications to adjust transmission rates and prevent buffer overflow, by defining thresholds and employing a gap credit counter to manage pause frame insertion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If MACsec encryption is applied to secure network links, then data confidentiality and integrity are improved, but packet size increases causing transmission time to increase and buffer overflow issues

Engineering Contradiction:

Improvedata confidentiality and integrityVSAvoidtransmission time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements flow control by having the PHY layer generate pause frames in advance when the transmitter buffer reaches a threshold, preventing buffer overflow before it occurs. This preliminary action allows the MAC layer to pause transmission proactively, accommodating the increased packet size from MACsec encryption without causing time loss or buffer overflow.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If MACsec encryption is applied to secure network links, then data confidentiality and integrity are improved, but packet size increases leading to buffer overflow conditions

Engineering Contradiction:

Improvedata confidentiality and integrityVSAvoidbuffer management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements a feedback mechanism where the PHY layer continuously monitors the transmitter buffer level and sends pause frames back to the MAC layer when the buffer reaches a threshold. This feedback loop automatically adjusts the transmission rate to prevent buffer overflow, simplifying buffer management while maintaining the security benefits of MACsec encryption.

Inventive Principle:

Principle #23Feedback

3Productivity

If transmission rate is increased to compensate for packet enlargement, then productivity is improved, but buffer overflow conditions worsen

Engineering Contradiction:

Improvetransmission rateVSAvoidbuffer overflow prevention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements dynamic flow control where the transmission rate is adjusted in real-time based on buffer conditions. The PHY layer dynamically sends pause frames to the MAC layer when the buffer reaches a threshold, allowing the system to maintain high productivity during normal operation while automatically reducing the transmission rate when buffer conditions indicate potential overflow, thus preventing buffer overflow without permanently reducing productivity.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8897129B1Method and apparatus for implementing flow control in a network via a physical layer (PHY)

Publication Date: 2014.11.25 MARVELL ASIA PTE LTD

AI summary

Various embodiments provide a way to adjust transmission rates of a medium access controller (MAC) to a physical layer (PHY) to accommodate for packet expansions due to encryption that takes place in the PHY. In at least some embodiments, a communication interface between different MACs in a system is re-purposed to allow the PHY to communicate to a system MAC to notify the system MAC to pause and then resume, at an appropriate time, its packet transmissions.