Dynamic Resilient Links: Port Loopback for In-Flight Data Recovery
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Solution Overview
Problem
High-speed computer networks face challenges in maintaining system availability and reducing data loss due to hardware failures, such as failed devices or cables, which are not effectively addressed by existing mechanisms that lead to network bandwidth wastage, increased latency, and software overhead.
Innovation Solution
A computer system with devices configured to enter a loopback mode upon link failure, rerouting both acknowledged and unacknowledged data segments via an alternate path, utilizing a switch core and port logic elements with transmit replay buffers to ensure data integrity and system availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retransmission mechanisms (go-back-n, selective ACK) are used to correct transmitted frames, then data delivery reliability is improved, but network bandwidth is wasted and tail latency increases
Solution Approach 1:
The invention segments the data transmission at the link level by dividing packets into segments and tracking them individually through the transmit replay buffer. This allows selective retransmission of only failed segments rather than entire packets, improving bandwidth efficiency while maintaining reliability.
Solution Approach 2:
The transmit replay buffer acts as an intermediary mechanism between the sender and receiver. It stores transmitted segments and enables selective retransmission based on failure detection, mediating between the need for reliability and the cost of retransmission in terms of bandwidth and latency.
2Reliability
If checkpoint restart mechanisms are used to handle hard failures, then system availability is improved, but software overhead and processing delays increase
Solution Approach 1:
The system performs preliminary actions by maintaining a transmit replay buffer that continuously stores transmitted segments before failures occur. This pre-positioned buffer enables immediate local retransmission upon failure detection, eliminating the need to wait for checkpoint restoration and reducing software overhead.
Solution Approach 2:
The link layer performs self-service by detecting failures and initiating retransmission autonomously through the transmit replay buffer without requiring upper layer intervention or system-wide checkpoint restarts. This self-healing mechanism reduces software complexity while maintaining availability.
3Reliability
If loopback mode is entered upon link failure, then data packets are rerouted via alternate path without data loss, but device complexity increases
Solution Approach 1:
The port logic element is designed with multi-functionality, serving both normal data transmission and failure recovery modes through the same transmit replay buffer infrastructure. This universal design enables loopback mode operation without requiring separate dedicated hardware, managing complexity while ensuring data integrity.
Data Source
AI summary
A computer system includes two or more devices connected to each other. Each of the devices includes a switch core, port logic elements connected to the switch core that each include a transmit replay buffer and receive logic, and physical layers connected to the port logic elements. In response to a link failure between a first port logic element of a first device and a second device, the first port logic element enters a loopback mode. In the loopback mode, an in-flight data packet including acknowledged data segments and unacknowledged data segments is looped back from the transmit replay buffer and the port receive logic of the first port logic element to the switch core, and from the switch core to a second port logic element to avoid loss of in-flight data.