OneWAN is better than two: Unifying a split WAN architecture


Umesh Krishnaswamy, Microsoft; Rachee Singh, Microsoft and Cornell University; Paul Mattes, Paul-Andre C Bissonnette, Nikolaj Bjørner, Zahira Nasrin, Sonal Kothari, Prabhakar Reddy, John Abeln, Srikanth Kandula, Himanshu Raj, Luis Irun-Briz, Jamie Gaudette, and Erica Lan, Microsoft


Many large cloud providers operate two wide-area networks (WANs) — a software-defined WAN to carry inter-datacenter traffic and a standards-based WAN for Internet traffic. Our experience with operating two heterogeneous planet-scale WANs has revealed the operational complexity and cost inefficiency of the split-WAN architecture. In this work, we present the unification of Microsoft's split-WAN architecture consisting of SWAN and CORE networks into ONEWAN. ONEWAN serves both Internet and inter-datacenter traffic using software-defined control. ONEWAN grappled with the order of magnitude increase in network and routing table sizes. We developed a new routing and forwarding paradigm called traffic steering to manage the increased network scale using existing network equipment. Increased network and traffic matrix size posed scaling challenges to SDN traffic engineering in ONEWAN. We developed techniques to find paths in the network and chain multiple TE optimization solvers to compute traffic allocations within a few seconds. ONEWAN is the first to apply software-defined techniques in an Internet backbone and scales to a network that is 10× larger than SWAN.

NSDI '23 Open Access Sponsored by
King Abdullah University of Science and Technology (KAUST)

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@inproceedings {286459,
author = {Umesh Krishnaswamy and Rachee Singh and Paul Mattes and Paul-Andre C Bissonnette and Nikolaj Bj{\o}rner and Zahira Nasrin and Sonal Kothari and Prabhakar Reddy and John Abeln and Srikanth Kandula and Himanshu Raj and Luis Irun-Briz and Jamie Gaudette and Erica Lan},
title = {{OneWAN} is better than two: Unifying a split {WAN} architecture},
booktitle = {20th USENIX Symposium on Networked Systems Design and Implementation (NSDI 23)},
year = {2023},
isbn = {978-1-939133-33-5},
address = {Boston, MA},
pages = {515--529},
url = {},
publisher = {USENIX Association},
month = apr,

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