GFP Frame Sequence ID for WDM Path Switching
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Solution Overview
Problem
Fibre Channel and similar protocols face issues with frame duplication and loss over extended distances due to differences in length between working and backup paths in fiber optic networks, leading to potential data errors and system failures.
Innovation Solution
Incorporating sequence identification numbers and session identification numbers in data headers, along with buffering data on both paths, to ensure accurate frame delivery and prevent duplication or loss during path switching, using GFP encapsulated SONET data and WDM equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If data is transmitted over extended distance fiber optic links using WDM equipment with working and backup paths, then channel extension capability is improved, but frame duplication and loss occur due to path length differences
Solution Approach 1:
The patent applies preliminary action by adding sequence identification numbers and session identification numbers to data frames before transmission. This allows the receiving end to identify and eliminate duplicate frames that arrive due to path length differences, preventing frame duplication issues before they compromise data integrity
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of identification numbers (sequence ID and session ID) that mediate between the working and backup paths. These identifiers allow the receiving end to distinguish between legitimate frames and duplicates, resolving the reliability issue caused by path length variations
2Reliability
If protection switchover is implemented from working path to backup path, then path failure protection is improved, but frame loss occurs during the 50ms switchover period
Solution Approach 1:
The patent uses preliminary action by pre-tagging frames with sequence and session identification numbers before switchover occurs. This enables the receiving end to track which frames were sent before the switch and which are new, preventing both frame loss and duplicate frame acceptance during the protection switchover period
3Reliability
If sequence identification numbers and session identification numbers are added to data headers, then frame duplication and loss are prevented, but data transmission overhead increases
Solution Approach 1:
The patent applies parameter changes by using compact identification number formats in the frame headers. The sequence ID and session ID are designed to provide sufficient discrimination capability while minimizing the number of bits required, thus preventing frame duplication and loss while keeping the overhead increase to a minimum
Data Source
AI summary
A sequence identification number is added to a header in each Generic Framing Procedure (GFP) frame. The byte sequence identification number identifies frames, preventing duplication or loss of exchanges, sequences, and frames. When this feature is enabled, a remote wavelength division multiplexing (WDM) node automatically checks the header to ensure that no duplication or loss occurs. The remote WDM node does not need to buffer data, instead the remote WDM node only needs to keep track of the sequence identification number information. A session identification number is also added to the header information, which allows the WDM node to keep track of which session was under way in the event that all connections between nodes across the WDM network are lost.