SAS DONE Primitives for Orderly Connection Closure
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Solution Overview
Problem
Current Serial Attached SCSI (SAS) protocols face challenges in maintaining stable connections due to limited availability of DONE primitives, leading to abrupt disconnections and potential data loss when communication issues arise, such as credit timeouts or unacknowledged frames.
Innovation Solution
Introduction of new DONE primitives, including DONE (CREDIT TIME-OUT) and DONE (ACK/NAK TIME-OUT), which provide additional information on connection closure conditions, allowing for orderly disconnection and reducing the likelihood of abrupt breaks by indicating specific issues, enabling the ports to manage connections more effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional connection closure methods are used in SAS protocols, then the system structure remains simple, but abrupt disconnections occur and data loss happens when communication issues arise
Solution Approach 1:
The patent segments the connection closure process by introducing multiple distinct DONE primitives (DONE(CREDIT TIMEOUT), DONE(ACK/NAK TIMEOUT), DONE(NORMAL)) to handle different communication failure scenarios separately. Each primitive provides specific information about the closure reason, enabling targeted responses rather than using a single generic closure method.
Solution Approach 2:
The patent implements feedback mechanisms where the DONE primitives carry information about the closure reason back to the other end of the connection. This allows the receiving system to understand why the connection is closing and respond appropriately, such as by initiating recovery procedures or cleaning up resources in a controlled manner.
2Reliability
If more DONE primitives are introduced to handle various timeout scenarios, then connection management improves and data loss reduces, but the protocol becomes more complex
Solution Approach 1:
The patent creates a universal DONE primitive structure that can serve multiple functions through different variants. The base DONE primitive handles normal closure, while DONE(CREDIT TIMEOUT) and DONE(ACK/NAK TIMEOUT) handle specific error conditions. This multi-functional approach consolidates various closure scenarios into a unified framework rather than creating separate protocols for each case.
Solution Approach 2:
The patent changes the parameter of the DONE primitive by adding a reason indicator that specifies the closure cause. This parameter modification allows the same primitive structure to convey different meanings (normal closure vs. timeout closure), enabling richer information transmission without fundamentally changing the protocol architecture.
3Reliability
If abrupt disconnections are prevented through better connection management, then data loss is reduced, but the connection establishment and management process takes more time
Solution Approach 1:
The patent applies preliminary action by establishing the DONE primitive exchange mechanism before actual data transmission issues occur. The connection management system is pre-configured to use appropriate DONE primitives based on detected conditions, allowing for proactive rather than reactive connection management. This reduces the time needed during actual failure events because the response protocol is already in place.
Data Source
AI summary
A method to provide more opportunities to close a connection in an orderly fashion and avoid abrupt break of the connection. A device and a system operable to practice such as method.