Enhancements to P4TG: Histogram-Based RTT Monitoring in the Data Plane

TL;DR

This paper introduces a histogram-based RTT measurement method for P4TG, enabling accurate, line-rate analysis without sampling by converting range matching into ternary entries, improving data plane measurement precision.

Contribution

It presents a novel range-to-prefix conversion algorithm for histogram-based RTT measurement in P4TG, enhancing accuracy and efficiency in data plane RTT analysis.

Findings

Histogram-based RTT measurement matches theoretical RTT distributions.

Range-to-prefix conversion enables hardware-efficient range matching.

Evaluation shows improved RTT measurement accuracy.

Abstract

Modern traffic generators are essential tools for evaluating the performance of network environments. P4TG is a P4-based traffic generator implemented for Intel Tofino switches that offers high-speed packet generation with fine-grained measurement capabilities. However, P4TG samples time-based metrics such as the round-trip time (RTT) in the data plane and collects them at the controller. This leads to a reduced accuracy. In this paper, we introduce a histogram-based RTT measurement feature for P4TG. It enables accurate analysis at line rate without sampling. Generally, histogram bins are modeled as ranges, and values are matched to a bin. Efficient packet matching in hardware is typically achieved using ternary content addressable memory (TCAM). However, representing range matching rules in TCAM poses a challenge. Therefore, we implemented a range-to-prefix conversion algorithm that models range matching with multiple ternary entries. This paper describes the data plane implementation and runtime configuration of RTT histograms in P4TG. Further, we discuss the efficiency of the ternary decomposition. Our evaluation demonstrates the applicability of the histogram-based RTT analysis by comparing the measured values with a configured theoretical distribution of RTTs.