TCP Trip Time Estimation Through Sparse Middlebox Sampling
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Solution Overview
Problem
The presence of middleboxes in network communication disrupts traditional methods of monitoring Transport Control Protocol (TCP) performance, as they modify and inspect packets without providing TCP flow markers, making it difficult for network administrators to evaluate and improve communication performance, especially in scenarios where endpoints have limited processing capabilities.
Innovation Solution
A system at the middlebox samples a subset of TCP packets to estimate performance characteristics like round trip time, throughput, and window size by generating time stamps and sequence/acknowledgment numbers, using interpolation for un-sampled packets, with minimal impact on the connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional TCP performance monitoring methods are used at endpoints, then measurement accuracy is improved, but device complexity and processing burden increase
Solution Approach 1:
The patent introduces a middlebox as an intermediary component that performs TCP performance monitoring functions. The middlebox intercepts TCP packets between endpoints, generates synthetic acknowledgments with timestamps, and calculates round-trip times without requiring complex processing at the endpoints. This mediator approach transfers the measurement complexity from resource-constrained endpoints to a more capable intermediate device.
Solution Approach 2:
The patent creates a copy of the TCP acknowledgment flow by generating synthetic ACK packets at the middlebox. Instead of requiring endpoints to perform complex measurements on actual traffic, the system creates timestamped copies of acknowledgment packets that carry measurement information. These synthetic packets enable performance monitoring while keeping endpoint processing simple.
2Productivity
If middleboxes inspect and modify TCP packets, then network optimization capability is improved, but TCP flow marker information is lost
Solution Approach 1:
The patent applies preliminary action by embedding timestamps and sequence numbers into synthetic acknowledgment packets before they are injected into the TCP stream. The middlebox pre-calculates round-trip times and attaches this measurement data to the synthetic ACK packets, ensuring that performance information is preserved and transmitted along with the data flow without requiring post-processing or additional measurement mechanisms.
3Productivity
If sparse packet sampling is used at the middlebox, then processing overhead is reduced, but measurement completeness decreases
Solution Approach 1:
The patent changes the parameter being measured from requiring complete packet inspection to using sparse sampling of key packets. By selectively sampling packets and using interpolation techniques for unsampled intervals, the system achieves acceptable measurement precision with reduced processing overhead. The middlebox adjusts its sampling rate and interpolation strategy based on traffic patterns and performance requirements.
Data Source
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AI summary
A method (300) includes sparsely sampling, at a middled ox (160), a plurality of packets (170) from a transport control protocol (TCP) connection (180) between a source endpoint (190) and a destination endpoint through the middlebox. For each packet of the sampled plurality of packets, the method includes generating a time stamp (212) when the packet is sampled and recording a sequence number (172) and an acknowledgement number (174) for the respective packet. The acknowledgement number is recorded when the acknowledgement number exists for the respective packet. The method also includes generating an estimated performance characteristic (202) for the TCP connection between the source endpoint and the destination endpoint through the middlebox over the period of time based on at least two of a respective time stamp, a respective sequence number, or a respective acknowledgement number from one or more of the sampled plurality of packets.