TRILL Access Device Equal-Cost Multi-Path Forwarding Entries

Solution Overview

Problem

In TRILL networks, layer 3 forwarding fails due to a failure of the Reverse Path Forwarding (RPF) check caused by the access device learning a correspondence among virtual MAC addresses and virtual nicknames of a gateway aggregation group with ports, leading to inconsistent outbound paths.

Innovation Solution

The access device stores and uses equal-cost multi-path forwarding entries that include virtual MAC addresses, identifiers for each gateway device, and outbound interfaces, allowing it to encapsulate and forward packets based on these entries, ensuring consistent backhaul paths with the original paths for successful RPF checks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the access device learns a correspondence among virtual MAC addresses and virtual nicknames of a gateway aggregation group with ports based on MAC address table, then packet forwarding can be performed, but the RPF check fails due to inconsistent outbound paths

Engineering Contradiction:

Improvepacket forwarding capabilityVSAvoidRPF check success rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The forwarding entry is segmented into multiple components: virtual MAC address, virtual nickname, and multiple outbound ports. This segmentation allows the system to maintain separate path information for different gateways while using a unified virtual MAC address, enabling both load sharing and consistent backhaul paths.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent adds a new dimension to the forwarding table by including both virtual MAC addresses and specific gateway device identifiers with their respective outbound ports. This multi-dimensional approach allows the access device to perform RPF checks based on the specific gateway device that originally sent the packet, rather than just the virtual MAC address, thereby resolving the path inconsistency issue.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If multiple gateways are aggregated into one gateway aggregation group with virtual MAC address for load sharing, then load distribution is improved, but backhaul path consistency deteriorates

Engineering Contradiction:

Improveload sharing capabilityVSAvoidbackhaul path consistency

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The forwarding entry is segmented into multiple components: virtual MAC address, virtual nickname, and multiple outbound ports. This segmentation allows the system to maintain separate path information for different gateways while using a unified virtual MAC address, enabling both load sharing and consistent backhaul paths.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system implements feedback by recording the specific outbound port used to receive packets from each gateway device in the aggregation group. When performing RPF checks, the access device uses this recorded port information to verify the backhaul path, ensuring that return traffic follows the same path as the original traffic, thus maintaining path consistency despite load sharing.

Inventive Principle:

Principle #23Feedback

3Device complexity

If the access device uses a single MAC address table for forwarding, then forwarding simplicity is maintained, but path tracking accuracy decreases

Engineering Contradiction:

Improveforwarding table structureVSAvoidpath identification accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent adds a new dimension to the forwarding table by including both virtual MAC addresses and specific gateway device identifiers with their respective outbound ports. This multi-dimensional approach allows the access device to perform RPF checks based on the specific gateway device that originally sent the packet, rather than just the virtual MAC address, thereby resolving the path inconsistency issue.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The forwarding table structure is designed to be multi-functional: it can perform both standard MAC address-based forwarding and RPF checks with path tracking using the same table. By including virtual MAC addresses, virtual nicknames, and outbound port information together, the table serves dual purposes without requiring separate data structures, thus maintaining simplicity while improving accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10050877B2Packet forwarding method and apparatus

Publication Date: 2018.08.14 HUAWEI TECH CO LTD

AI summary

The present application discloses a packet forwarding method and apparatus. An access device receives a first packet, where the first packet is an Ethernet packet, searches an equal-cost multi-path forwarding entry for a matched equal-cost path according to a destination MAC address of the Ethernet packet, where the equal-cost multi-path forwarding entry includes: a virtual MAC address corresponding to a gateway aggregation group, an identifier of each gateway device in the gateway aggregation group, and an outbound interface corresponding to the identifier of each gateway device, where the identifier is used to uniquely identify a gateway device in a large layer 2 network; and if N matched equal-cost paths are found, encapsulates the first packet into a second packet according to a first path in the N matched equal-cost paths, and forwards the second packet according to an outbound interface of the first path.