PTP Frame Time Stamping via MAC Identifier Extraction

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Solution Overview

Problem

The existing integration of Precise Time Protocol (PTP) and Media Access Control (MAC) security function (MACsec) in network devices faces inaccuracies in time-of-the-day data generation due to delays in time stamping encrypted PTP frames during transmission and reception, as the Ethertype field is encrypted, making it difficult to identify and time stamp PTP frames promptly.

Innovation Solution

The system includes a MAC module and a PTP module configured to generate and identify encrypted PTP frames, allowing for immediate time stamping before transmission and accurate time stamping upon reception by using identifiers and a parsing module to determine frame types, ensuring that time stamps closely correspond to actual transmission and reception times.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If all frames are encrypted to maintain security, then security is improved, but time stamping accuracy deteriorates because the Ethertype field is encrypted and PTP frames cannot be identified promptly

Engineering Contradiction:

ImprovesecurityVSAvoidtime stamping accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The frame structure is segmented into an unencrypted header portion (containing Ethertype identifier) and an encrypted payload portion. This allows the Ethertype field to remain accessible for frame identification while the sensitive data remains encrypted, resolving the contradiction between security and time stamping accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The Ethertype identifier is extracted from the encrypted portion and placed in an unencrypted header section. This extraction allows the PTP module to identify PTP frames without decryption, enabling accurate time stamping while maintaining encryption of the actual data payload.

Inventive Principle:

Principle #2Taking out (Extraction)

2Measurement precision

If decryption is performed before time stamping to identify PTP frames, then frame identification accuracy is improved, but time stamping delay increases

Engineering Contradiction:

Improveframe identification accuracyVSAvoidtime stamping delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The Ethertype identifier is prepared in advance in an unencrypted state in the frame header, before any decryption operations are needed. This preliminary arrangement allows immediate frame identification and time stamping upon receipt, eliminating the time loss that would result from decrypting frames to identify them.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If PTP frames are transmitted unencrypted to enable immediate time stamping, then time stamping accuracy is improved, but security deteriorates

Engineering Contradiction:

Improvetime stamping accuracyVSAvoidsecurity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

Different portions of the frame have different encryption states: the header (containing Ethertype) remains unencrypted locally to enable identification and time stamping, while the payload portion is encrypted locally to maintain security. This local quality differentiation resolves the contradiction between time stamping accuracy and security.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP2316196B1Method and apparatus for integrating precise time protocol and media access control security in network elements

Publication Date: 2019.02.27 MARVELL WORLD TRADE LTD

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AI summary

A system includes a medium access control (MAC) module and a precise time protocol (PTP) module. The MAC module is configured to generate an identifier for a PTP frame, generate an encrypted PTP frame by encrypting the PTP frame, and output the identifier. The PTP module is configured to receive the identifier, identify the encrypted PTP frame based on the identifier in response to the encrypted PTP frame being output from the MAC module, and time stamp the encrypted PTP frame prior to the encrypted PTP frame being transmitted.