RDMA Multipath Routing Using Hardware Congestion Weights

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Solution Overview

Problem

Current RDMA technologies, such as RoCE, lack a mechanism to spread a single transport flow across multiple network paths, leading to congestion when multiple flows are set to the same link, even when other routes are underutilized, and require significant software overhead for software layer solutions.

Innovation Solution

Implementing a hardware-based multipath context that enables network controllers to spread a transport flow across multiple paths by using network routing identifiers, monitoring route congestion, and providing a fast recovery mechanism without software intervention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If RDMA technology uses a single network path for all packets of a transport flow, then data transfer efficiency is maintained, but network utilization is poor and congestion occurs when multiple flows use the same link

Engineering Contradiction:

Improvedata transfer efficiencyVSAvoidnetwork path utilization

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent segments a single transport flow into multiple sub-flows that can be distributed across different network paths. The multipath context divides the flow at the packet level, allowing individual packets to be routed through different paths based on congestion conditions, thereby improving both data transfer efficiency and network path utilization simultaneously

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic path selection by monitoring route congestion in real-time and adjusting packet routing accordingly. The system dynamically switches between different network paths based on current network conditions, enabling the system to adapt to changing network topology and congestion states without sacrificing data transfer efficiency

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If software layer solutions are used to spread traffic across multiple paths, then network utilization improves, but software overhead and computational complexity increase significantly

Engineering Contradiction:

Improvenetwork path utilizationVSAvoidsoftware overhead

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces software-based multipath routing mechanisms with hardware implementation in the network controller. The multipath context is stored in hardware registers, and path selection is performed through hardware logic that examines packet headers and routing tables directly, eliminating the need for complex software processing and reducing overhead while maintaining network path utilization improvements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a hardware multipath context as an intermediary between the packet processing unit and the routing decision. This hardware context stores path information and congestion state, acting as a mediator that enables fast path selection without requiring extensive software intervention, thus reducing software overhead while maintaining adaptability

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If all packets of a transport flow travel across the same network path, then packet ordering is simplified, but route selection flexibility is limited and congestion cannot be avoided

Engineering Contradiction:

Improvepacket orderingVSAvoidcongestion avoidance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent segments packets into different sub-flows that can be sent through different paths. By dividing the transport flow at the packet level and using multipath context to track each sub-flow, the system maintains simplified packet ordering within each path while enabling flexible route selection across multiple paths to avoid congestion

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements feedback mechanisms where the network controller monitors route congestion and adjusts packet routing accordingly. Congestion information is fed back into the multipath context, which then uses this information to make future routing decisions, enabling the system to avoid congestion while maintaining manageable packet ordering through hardware-assisted path selection

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20250358219A1Routing transport flows in a transport layer over multiple paths in a network layer

Publication Date: 2025.11.20 MELLANOX TECHNOLOGIES LTD(IL)

AI summary

Technologies for spreading packets of transport flows across multiple network paths are described. A network controller includes a transport layer and a network layer. The transport layer includes a flow scheduler to schedule a transport flow from one of a plurality of transport flows. The network layer includes multipath logic to receive packets from the transport flow and select which path of a plurality of paths to a destination to use for the packets based on path congestion weights corresponding to the plurality of paths.