Fibre Channel over Ethernet Encoding via 256/257 Scheme
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Solution Overview
Problem
Fibre Channel protocols face errors when extended over Ethernet networks due to improper interpretation of K28.5 characters as frame delimiters, leading to incorrect word alignment and data transmission issues.
Innovation Solution
A 256/257 encoding scheme is implemented, where Fibre Channel words are reordered, and a syncbit is prepended to indicate the presence of ordered sets, allowing correct identification and repositioning of control characters within Ethernet packets, ensuring transparent data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Fibre Channel protocol is extended over Ethernet networks, then geographic dispersion capability is improved, but data transmission reliability deteriorates due to K28.5 character misinterpretation
Solution Approach 1:
The patent introduces an intermediary encoding layer (256/257 encoding) between Fibre Channel and Ethernet protocols. This intermediary translates FC's 8B/10B encoded K28.5 characters into a different representation that Ethernet can transmit without misinterpreting as frame delimiters, while maintaining FC protocol functionality at the endpoints.
Solution Approach 2:
The patent changes the parameter representation of control characters by applying 256/257 encoding. This encoding scheme modifies how K28.5 characters are represented in the transmitted data stream, changing their byte patterns so they no longer match Ethernet's frame delimiter signatures, thereby preventing misinterpretation while preserving the original FC protocol semantics.
2Reliability
If 256/257 encoding scheme is implemented, then data transmission reliability is improved, but device complexity increases due to reordering and syncbit operations
Solution Approach 1:
The patent applies preliminary encoding actions to the data stream before transmission. The 256/257 encoding is performed in advance on all control characters, and syncbits are prepended to groups of words beforehand. This preliminary processing ensures that when data is received, the decoding can proceed systematically without requiring complex real-time analysis, thereby managing device complexity.
Solution Approach 2:
The patent segments the Fibre Channel data stream into groups of words, with each group receiving a syncbit prefix. This segmentation allows the encoding/decoding operations to be performed on manageable chunks rather than continuous streams, simplifying the implementation logic and reducing the complexity of state management in the encoding/decoding devices.
3Measurement precision
If ordered sets are reordered in transmitted data, then word alignment accuracy is improved, but processing time increases due to repositioning operations
Solution Approach 1:
The reordering of ordered sets and prepending of syncbits are performed as preliminary actions during the encoding phase before transmission. This means that when data is received, the alignment information is already in place, and the decoder can process words sequentially without requiring complex real-time reordering operations, thereby minimizing the time penalty.
Data Source
AI summary
In one embodiment, data words and ordered sets in a Fibre Channel data stream are formed into a group and the ordered sets are moved to the beginning word positions of the group. The ordered sets are encoded so that a control character in the first byte of the ordered set is replaced with a control code byte encoding the original location of the ordered set in the group, the identity of the control character replaced by the control code byte, and whether the following word is an ordered set.