DCB Path Selection for LAG Topologies

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Solution Overview

Problem

Existing SAN traffic handling systems in LAG topologies fail to utilize DCB-enabled paths effectively, leading to traffic drop when a path is congested, even if alternative DCB-enabled paths are available, due to the requirement that all LAG port channels must be operationally up for lossless communication.

Innovation Solution

Implementing a DCB-based path selection system that automatically identifies and utilizes DCB-enabled links by configuring hardware forwarding tables to route DCB-enabled traffic through sub-trunks comprising only operational links, while non-DCB traffic is forwarded through regular trunks, and utilizing INLs when all local LAG port channels are down.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If all LAG port channel members must be operationally up for lossless communication, then DCB-enabled traffic can be forwarded reliably, but SAN traffic is dropped when a path is congested even if alternative DCB-enabled paths exist

Engineering Contradiction:

Improvelossless communicationVSAvoidtraffic forwarding efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the LAG port channel into two distinct groups: a first set of member links for regular traffic and a second set of member links for DCB-enabled traffic. This segmentation allows DCB traffic to be forwarded independently through DCB-enabled paths even when other LAG members are down, resolving the contradiction by enabling reliable lossless communication without requiring all members to be operational.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic path selection where the system automatically adapts its forwarding behavior based on the operational status of LAG members. When DCB-enabled paths are available, the system dynamically routes DCB traffic through those paths; when all LAG members are down, it falls back to INLs. This dynamic adaptation maintains reliability while improving productivity by utilizing available paths.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If DCB traffic follows regular LAG hashing mechanism when some port channel members are down, then traffic can be forwarded, but SAN traffic is dropped due to congestion on non-DCB paths

Engineering Contradiction:

Improvetraffic forwardingVSAvoidSAN traffic delivery

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies different forwarding qualities to different traffic types: DCB-enabled traffic receives priority treatment and is routed through DCB-enabled paths with lossless characteristics, while regular traffic uses standard LAG hashing. This local quality differentiation ensures that SAN traffic maintains high reliability through dedicated paths without affecting overall ease of operation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces DCB-enabled paths as an intermediary layer between the incoming SAN traffic and the final destination. These intermediary paths provide a dedicated lossless conduit for DCB traffic, mediating between the need for traffic forwarding and the requirement for reliable SAN traffic delivery, thereby preventing drops.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If INL is used only when all LAG port channels are down, then ICL can provide backup path, but DCB traffic cannot utilize available DCB-enabled paths through ICL when some LAG members are down

Engineering Contradiction:

Improvepath utilization flexibilityVSAvoidDCB traffic forwarding

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the available paths into DCB-enabled paths (including ICLs) and non-DCB paths, allowing independent selection based on traffic type. This segmentation enables DCB traffic to utilize ICLs for reliable forwarding even when some LAG members are down, significantly improving adaptability while maintaining reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic path selection where the system continuously monitors the operational status of LAG members and automatically switches between DCB-enabled paths and INLs as needed. This dynamic behavior maximizes path utilization flexibility while ensuring reliable DCB traffic forwarding through available lossless paths.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11349752B2Path selection systems and methods for data traffic for link aggregation group topologies

Publication Date: 2022.05.31 DELL PROD LP

AI summary

Data Center Bridge (DCB)-based path selection methods and systems reduce packet loss in a network system comprising a Link Aggregation Group (LAG) topology. In embodiments, once traffic received at a LAG node and identified as DCB traffic, links whose DCB status are identified as “up” are assigned to a LAG sub-trunk that may be used to forward the DCB traffic on the LAG trunk, while non-DCB traffic is forwarded to any member of the LAG, irrespective of DCB status. In addition, DCB traffic received from a LAG peer node, which sends traffic on an inter-node link (INL) when no DCB-enabled links to a downstream device are present, is identified as DCB traffic and forwarded on a LAG sub-trunk that comprises DCB-enabled links. An egress mask that indicates to not forward the traffic received at the LAG node on the INL may be overridden, such that DCB traffic may be forwarded.