Azure Accelerated Networking: SmartNICs in the Public Cloud


Daniel Firestone, Andrew Putnam, Sambhrama Mundkur, Derek Chiou, Alireza Dabagh, Mike Andrewartha, Hari Angepat, Vivek Bhanu, Adrian Caulfield, Eric Chung, Harish Kumar Chandrappa, Somesh Chaturmohta, Matt Humphrey, Jack Lavier, Norman Lam, Fengfen Liu, Kalin Ovtcharov, Jitu Padhye, Gautham Popuri, Shachar Raindel, Tejas Sapre, Mark Shaw, Gabriel Silva, Madhan Sivakumar, Nisheeth Srivastava, Anshuman Verma, Qasim Zuhair, Deepak Bansal, Doug Burger, Kushagra Vaid, David A. Maltz, and Albert Greenberg, Microsoft


Modern cloud architectures rely on each server running its own networking stack to implement policies such as tunneling for virtual networks, security, and load balancing. However, these networking stacks are becoming increasingly complex as features are added and as network speeds increase. Running these stacks on CPU cores takes away processing power from VMs, increasing the cost of running cloud services, and adding latency and variability to network performance.

We present Azure Accelerated Networking (AccelNet), our solution for offloading host networking to hardware, using custom Azure SmartNICs based on FPGAs. We define the goals of AccelNet, including programmability comparable to software, and performance and efficiency comparable to hardware. We show that FPGAs are the best current platform for offloading our networking stack as ASICs do not provide sufficient programmability, and embedded CPU cores do not provide scalable performance, especially on single network flows.

Azure SmartNICs implementing AccelNet have been deployed on all new Azure servers since late 2015 in a fleet of >1M hosts. The AccelNet service has been available for Azure customers since 2016, providing consistent <15μs VM-VM TCP latencies and 32Gbps throughput, which we believe represents the fastest network available to customers in the public cloud. We present the design of AccelNet, including our hardware/software co-design model, performance results on key workloads, and experiences and lessons learned from developing and deploying AccelNet on FPGA-based Azure SmartNICs.

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@inproceedings {211249,
author = {Daniel Firestone and Andrew Putnam and Sambhrama Mundkur and Derek Chiou and Alireza Dabagh and Mike Andrewartha and Hari Angepat and Vivek Bhanu and Adrian Caulfield and Eric Chung and Harish Kumar Chandrappa and Somesh Chaturmohta and Matt Humphrey and Jack Lavier and Norman Lam and Fengfen Liu and Kalin Ovtcharov and Jitu Padhye and Gautham Popuri and Shachar Raindel and Tejas Sapre and Mark Shaw and Gabriel Silva and Madhan Sivakumar and Nisheeth Srivastava and Anshuman Verma and Qasim Zuhair and Deepak Bansal and Doug Burger and Kushagra Vaid and David A. Maltz and Albert Greenberg},
title = {Azure Accelerated Networking: SmartNICs in the Public Cloud},
booktitle = {15th {USENIX} Symposium on Networked Systems Design and Implementation ({NSDI} 18)},
year = {2018},
isbn = {978-1-931971-43-0},
address = {Renton, WA},
pages = {51--66},
url = {},
publisher = {{USENIX} Association},