Credited Network Buffer Reallocation Without Port Flaps
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Solution Overview
Problem
Existing credit-based flow control mechanisms in networks like Fibre Channel and InfiniBand require port flaps to adjust buffer credits, leading to undesirable frame drops and downtime, especially when reallocating buffers across ports or virtual lanes.
Innovation Solution
Implement a non-disruptive method to move buffers/credits across operational ports or virtual lanes using receive and transmit credit hold features, enabling intelligent buffer management without frame drops through a two-stage handshake protocol and internal messaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If buffer credits are adjusted by bringing links down and reallocating during link up, then buffer reallocation is achieved, but frame drops and downtime occur
Solution Approach 1:
The patent implements dynamic buffer credit adjustment during operational links by introducing receive credit hold and transmit credit hold mechanisms. These allow the system to dynamically reconfigure buffer credits without physical link disruption, transforming a static allocation system into a dynamic one that can adapt to changing buffer needs while maintaining continuous operation.
Solution Approach 2:
The patent uses credit hold mechanisms as intermediaries between the buffer allocation system and the frame transmission system. The receive credit hold and transmit credit hold act as mediating layers that decouple buffer reallocation operations from active frame transmission, allowing buffer reconfiguration without directly impacting ongoing communications.
2Ease of operation
If buffer credits are reallocated during operational links, then buffer management flexibility improves, but link stability deteriorates
Solution Approach 1:
The patent applies preliminary action by having ports signal their intent to reallocate buffers before actually doing so. The initiate buffer credit reallocation message serves as a preliminary notification to the peer port, allowing the system to prepare for the reallocation in advance and coordinate the transition smoothly without surprising the active frame transmission system.
Solution Approach 2:
The patent implements feedback mechanisms where ports acknowledge receipt of reallocation messages and provide status information about buffer credit changes. This feedback loop ensures that both ends of the link are synchronized during the reallocation process, maintaining stability while enabling flexible buffer management.
3Adaptability or versatility
If port flapping is used to adjust buffers, then buffer credits can be changed, but downtime increases
Solution Approach 1:
The patent ensures continuity of useful action by enabling buffer credit reallocation to occur while links remain operational and active. The receive credit hold and transmit credit hold mechanisms allow the system to continue processing frames during the buffer reconfiguration process, eliminating the need to bring links down and thus maintaining continuous productive operation.
Data Source
AI summary
Techniques for moving buffers between ports, or virtual lanes of a port, of a networking device of a credited network while maintaining the ports in an active state without dropping any frames. The techniques may include determining that a number of buffers are to be reallocated from a first port of a networking device to a second port of the networking device. The techniques may also include causing a peer port connected to the first port to decrement, by the number, a transmit credit counter associated with the peer port. Based at least in part on determining that the peer port decremented the transmit credit counter, the first port may release the number of the buffers from a buffer pool associated with the first port, and the number of the buffers may be reallocated to the second port.