Bonding Engine FCS Inversion for Loopback Prevention

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Solution Overview

Problem

The standard Ethernet in the First Mile (EFM) bonding protocol is susceptible to looping back packets during a loopback condition, leading to network feed disablement due to MAC address detection, causing issues like entire shelf network feed disablement in Multi-Service Access Platforms.

Innovation Solution

Inverting the Frame Check Sequence (FCS) in data packets within a bonding engine to prevent propagation during loopback conditions, with additional bits in the Bonding Aggregation Control Protocol (BACP) Protocol Data Unit (PDU) indicating the ability to send and receive inverted FCS, and negotiating which engine performs the inversion based on MAC address.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the standard EFM bonding protocol is used, then packet transmission across bonded subscriber lines is enabled, but packets are looped back during loopback conditions causing network feed disablement

Engineering Contradiction:

Improvenetwork feed stabilityVSAvoidpacket loopback propagation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the Frame Check Sequence (FCS) in data packets transmitted over bonded subscriber lines. This inversion causes looped-back packets to fail FCS validation at the receiving end, effectively preventing harmful packet propagation during loopback conditions while maintaining normal packet transmission functionality

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent converts the potentially harmful loopback condition into a detectable and manageable event by using the inverted FCS mechanism. When packets are looped back, the inverted FCS causes them to fail validation, allowing the system to identify and disable only the offending subscriber line rather than disabling the entire network feed

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If BACP loopback detection is implemented, then links in loopback condition are disabled, but packets received prior to BACP packet transmission pass through towards the network

Engineering Contradiction:

Improveloopback detection accuracyVSAvoidpacket propagation delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies FCS inversion to all data packets before transmission, creating a preliminary protective measure that prevents loopback propagation immediately at the packet level. This eliminates the time delay associated with waiting for BACP detection packets, as the protection is active continuously on every transmitted packet

Inventive Principle:

Principle #10Preliminary action

3Object-generated harmful factors

If FCS inversion is applied to prevent packet loopback, then packet propagation during loopback is blocked, but compatibility with legacy systems may be affected

Engineering Contradiction:

Improveloopback packet propagationVSAvoidprotocol compatibility

Core Design Contradiction:

Object-generated harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent applies FCS inversion selectively only to data packets transmitted over bonded subscriber lines, rather than universally to all network traffic. This localized application maintains compatibility with legacy systems and other network components that do not use FCS inversion, while providing loopback protection where needed

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9094174B2Bonding engine configured to prevent data packet feedback during a loopback condition

Publication Date: 2015.07.28 ADTRAN INC

AI summary

A system and method transmits data and receives data packets within a bonding engine. The data packets are fragmented into a plurality of packet fragments for communication across a bonded group of subscriber lines. A Frame Check Sequence (FCS) in the data packet is inverted on one direction of the bonding group to prevent any data packets from propagating towards the network during a loopback condition.