RDMA Packet Ordering Using Receipt Mapping for Multi-Path Throughput
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Solution Overview
Problem
Existing RDMA technologies in high-performance data centers are limited by packet ordering manners that restrict multi-path transmission, leading to suboptimal network bandwidth utilization due to requirements for fence ordering and strong ordering, which increase latency and hinder full utilization of network performance.
Innovation Solution
A packet transmission method that utilizes a mapping table to determine the receipt status of previous packets, allowing non-ordering packets to be sent without waiting, thereby optimizing the use of multi-path transmission and ensuring timely packet processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fence ordering is used to ensure packet receipt confirmation before sending, then packet delivery reliability is improved, but network latency increases
Solution Approach 1:
The patent segments packet transmission into two independent categories: ordering packets (requiring reliability) and non-ordering packets (allowing immediate transmission). This segmentation enables the system to apply different transmission strategies to different packet types, resolving the contradiction between reliability and latency by allowing non-ordering packets to bypass the confirmation waiting process while ordering packets maintain reliability guarantees.
Solution Approach 2:
The patent applies local quality by differentiating transmission requirements based on packet characteristics. Instead of uniform treatment, ordering packets receive strict receipt confirmation before transmission, while non-ordering packets receive immediate transmission permission. This localized differentiation of transmission quality attributes resolves the latency-reliability contradiction by applying appropriate strictness only where needed.
2Reliability
If strong ordering is used to ensure single-path transmission, then packet ordering is improved, but network bandwidth utilization deteriorates
Solution Approach 1:
The patent segments packet transmission into ordering and non-ordering categories, allowing multi-path transmission for non-ordering packets while maintaining single-path ordering for ordering packets. This segmentation enables simultaneous exploitation of multi-path bandwidth and preservation of ordering guarantees where required, resolving the contradiction between packet ordering and bandwidth utilization.
Solution Approach 2:
The patent applies partial ordering rather than complete strong ordering. By allowing non-ordering packets to use multi-path transmission, the system provides sufficient ordering only where necessary (for ordering packets) while permitting excessive path flexibility for non-ordering packets, thereby maximizing bandwidth utilization without compromising essential ordering requirements.
3Productivity
If multi-path transmission is implemented to increase bandwidth, then network throughput is improved, but packet ordering control deteriorates
Solution Approach 1:
The patent segments packets into ordering and non-ordering types with distinct transmission controls. Non-ordering packets can utilize multi-path transmission for high throughput, while ordering packets maintain controlled single-path transmission for ordering guarantees. This segmentation resolves the contradiction by allowing multi-path benefits without compromising ordering control where needed.
Solution Approach 2:
The patent applies local quality by providing different transmission quality attributes to different packet types. Ordering packets receive strict ordering control (single-path), while non-ordering packets receive relaxed control (multi-path). This localized differentiation enables simultaneous achievement of high throughput and reliable ordering control for packets that require it.
Data Source
AI summary
In a packet transmission in an interconnection network, a first device and a second device are connected using a queue pair (QP). The transmission includes: a transmit device locally storing a first mapping table and a send queue. The first mapping table stores an identifier of a packet received by a receive device, and the send queue stores a to-be-sent packet. When the to-be-sent first packet is a packet needing to be sent in order, the transmit device may determine, based on a packet identifier stored in the first mapping table, whether a previous packet of the first packet has been received by the peer end. Sending of a subsequent packet not needing to be sent in order may not be blocked, and bandwidth of the interconnection network can be fully utilized.