Norma: Towards Practical Network Load Testing


Yanqing Chen, State Key Laboratory for Novel Software Technology, Nanjing University and Alibaba Group; Bingchuan Tian, Alibaba Group; Chen Tian, State Key Laboratory for Novel Software Technology, Nanjing University; Li Dai, Yu Zhou, Mengjing Ma, and Ming Tang, Alibaba Group; Hao Zheng, Zhewen Yang, and Guihai Chen, State Key Laboratory for Novel Software Technology, Nanjing University; Dennis Cai and Ennan Zhai, Alibaba Group


Network load tester is important to daily network operation. Motivated by our experience with a major cloud provider, a practical load tester should satisfy two important requirements: (R1) stateful protocol customization, and (R2) real network traffic emulation (including high-throughput traffic generation and precise rate control). Despite the success of recent load testers, we found they fail to meet both above requirements. This paper presents Norma, a practical network load tester built upon programmable switch ASICs. To achieve the above requirements, Norma addresses three challenges: (1) modeling stateful protocols on the pipelined architecture of the ASIC, (2) generating replying packets with customized payload for stateful protocols, and (3) controlling mimicked traffic in a precise way. Specifically, first, Norma introduces a stateful protocol abstraction that allows us to program the logic of the state machine (e.g., control flow and memory access) on the programmable switch ASIC. Second, Norma proposes a novel multi-queue structure to generate replying packets and customize the payload of packets. Third and finally, Norma coordinates meters and registers to construct a multi-stage rate control mechanism capable of offering precise rate and burst control. Norma has been used to test the performance of our production network devices for over two years and detected tens of performance issues. Norma can generate up to 3 Tbps TCP traffic and 1 Tbps HTTP traffic.

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@inproceedings {286498,
author = {Yanqing Chen and Bingchuan Tian and Chen Tian and Li Dai and Yu Zhou and Mengjing Ma and Ming Tang and Hao Zheng and Zhewen Yang and Guihai Chen and Dennis Cai and Ennan Zhai},
title = {Norma: Towards Practical Network Load Testing},
booktitle = {20th USENIX Symposium on Networked Systems Design and Implementation (NSDI 23)},
year = {2023},
isbn = {978-1-939133-33-5},
address = {Boston, MA},
pages = {1733--1749},
url = {},
publisher = {USENIX Association},
month = apr,

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