PON Data Frame Fragmentation for Low-Latency Packet Transmission
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Solution Overview
Problem
In passive optical networks (PON), the transmission delay of service packets is high due to the requirement that the frame header must be sent in its entirety before the service packet can be transmitted, especially when the frame header length exceeds tens of bytes to thousands of bytes, which is problematic for scenarios requiring low delay and low jitter.
Innovation Solution
The optical line terminal (OLT) actively fragments the frame header into subframe headers, allowing packets to be sent between subframe headers, with each subframe header length limited to a preset value, and includes fields for carrying packets of varying priorities, enabling preemption of higher priority packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frame header is sent as a whole before the service packet, then the frame structure integrity is maintained, but the packet transmission delay increases significantly
Solution Approach 1:
The frame header is segmented into multiple sub-headers (first sub-header, second sub-header, etc.) that can be transmitted separately. This allows the service packet to be inserted between sub-headers, reducing the waiting time for packet transmission while maintaining frame integrity through proper reassembly at the receiver end.
2Adaptability or versatility
If the frame header length is increased to accommodate more bandwidth maps and PLOAM messages, then the network management capability is improved, but the packet transmission delay increases
Solution Approach 1:
By segmenting the extended frame header into multiple sub-headers, the system can accommodate more bandwidth maps and PLOAM messages while allowing packets to be transmitted between sub-headers. This resolves the contradiction by enabling both enhanced network management capability and reduced packet delay through the segmentation mechanism.
3Loss of time
If the frame header is fragmented into subframe headers, then the packet transmission delay is reduced, but the frame structure complexity increases
Solution Approach 1:
The frame header is divided into ordered sub-headers with clear sequencing information. Each sub-header contains identification and ordering fields that simplify the reassembly process at the receiver, reducing the actual complexity despite the fragmentation. This allows packet insertion between sub-headers while maintaining manageable structural complexity through systematic organization.
Solution Approach 2:
The sub-headers act as intermediaries between the original frame header structure and the packet data. They provide a structured interface that manages the complexity of fragmentation by establishing clear rules for insertion, ordering, and reassembly, thereby reducing the overall system complexity despite the fragmented structure.
Data Source
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Figure 3(a)~3(b)
Figure 4(a)
AI summary
This application provides a data frame fragmentation method, a data frame parsing method, and a related device. An OLT generates an original data frame. The original data frame includes a frame header and a packet. If a length of the frame header is greater than a first preset value, the OLT performs fragmentation on the frame header to obtain a target data frame. A length of each subframe header after the frame header is fragmented is less than or equal to the first preset value. The target data frame includes a plurality of codewords. At least one codeword includes a first field. Each codeword includes a second field. The at least one codeword further includes a third field. The first field is used for carrying the subframe header and a first packet having a low priority. The second field is used for carrying a check code. The third field is used for carrying a second packet having a high priority. A sending order of the first packet is after a subframe header with a front most sending order, and the sending order of the first packet is before a sending order of at least one subframe header. Further, the OLT sends the target data frame to an optical network unit ONU.