Header Compression Logic for Out-of-Order Packet Delivery
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Solution Overview
Problem
Existing header compression algorithms in packet-switched networks are not robust against packet reordering, which can lead to decompression failures and reduced compression efficiency, especially in channels that do not guarantee in-order delivery of packets.
Innovation Solution
The use of external information regarding the degree of packet misordering allows the compressor and decompressor to optimize their logic and parameters, such as the parameter p in the ROHC algorithm's LSB encoding and state transition configurations, to enhance robustness against misordering while maintaining packet loss tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If header compression is applied using standard algorithms (e.g., ROHC) assuming in-order delivery, then compression efficiency is improved and bandwidth is saved, but decompression failures occur when packets are reordered, reducing reliability
Solution Approach 1:
The patent applies preliminary action by having the compressor send the next expected packet sequence number in advance within the compressed header. This allows the decompressor to proactively detect reordering before attempting decompression, preventing decompression failures rather than reacting to them after they occur.
Solution Approach 2:
The patent implements feedback by having the decompressor compare the received packet sequence number with the expected sequence number and send appropriate feedback (ACK/NACK) to the compressor. This feedback mechanism allows the compressor to adapt its transmission strategy based on actual channel conditions and reordering patterns.
2Reliability
If the compressor sends full header packets frequently to maintain robustness against reordering, then decompression reliability is improved, but bandwidth consumption increases and compression efficiency decreases
Solution Approach 1:
The patent applies partial action by sending only the necessary next expected sequence number information in the compressed header rather than full header packets. This partial information is sufficient to enable reordering detection and maintain decompression reliability without the overhead of transmitting complete headers for every packet.
Solution Approach 2:
The patent changes the parameter being transmitted in compressed headers from traditional delta-encoded field values to the next expected packet sequence number. This parameter change enables the decompressor to detect reordering conditions while maintaining efficient compression ratios.
3Reliability
If the decompressor discards out-of-order packets to avoid decompression failures, then decompression reliability is maintained, but packet loss increases and throughput decreases
Solution Approach 1:
The patent applies preliminary action by enabling the decompressor to check the packet sequence number against the expected sequence number before attempting decompression. This preliminary check allows the decompressor to identify and handle reordered packets appropriately rather than blindly discarding them, reducing unnecessary packet loss.
Solution Approach 2:
The patent uses feedback to communicate reordering conditions between decompressor and compressor. When the decompressor detects reordering through sequence number comparison, it sends feedback that allows the compressor to adjust its transmission strategy, enabling potential recovery of reordered packets rather than their permanent loss.
Data Source
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AI summary
For use in packet-switched networks, a method is provided for using external information regarding the degree of misordering of packets, to make header compression more robust against such misordering.