Abstract Bio As the number, variety, and sophistication of Internet applications keeps growing and the number of client requests per time unit keeps increasing, datacenters are adopting hyperscale computing solutions to scale with the demand, and provide appropriate support for interactive services. As system size increases, the cost of the interconnection network grows faster than system size, thus becoming increasingly important to carefully design it to prevent overprovisioning. However, by doing so, the network operation point moves closer to saturation, and sudden traffic bursts may lead to congestion. This situation is aggravated by the recent introduction of flow control in datacenter networks to cope with RDMA requirements. The result is a massive performance degradation whenever some network region becomes congested. Moreover, performance degradation may remain for long even after the traffic bursts that congested the network have already been transmitted. This performance degradation is not compatible with trustworthiness.In this keynote, I will show why congestion appears in an interconnection network, how it propagates, and why performance may degrade so dramatically. Different kinds of congestion will be identified. Also, a global solution to address the congestion problem will be proposed. It consists of several complementary mechanisms that cooperate to address all kinds of congestion and operate at different time scales. Some of these mechanisms have been recently incorporated into commercial products and are being standardized.Keywords: Interconnection network, congestion management, datacenters Jose Duato is Professor in the Department of Computer Engineering (DISCA) at the Technical University of Valencia (Universitat Politècnica de València). His current research interests include interconnection networks, multicore and multiprocessor architectures, and accelerators for deep learning. He published over 500 refereed papers. According to Google Scholar, his publications received more than 16,000 citations. He proposed a theory of deadlock-free adaptive routing that has been used in the design of the routing algorithms for the Cray T3E supercomputer, the on-chip router of the Alpha 21364 microprocessor, and the IBM BlueGene/L supercomputer. He also developed RECN, a scalable congestion management technique, and a very efficient routing algorithm for fat trees that has been incorporated into Sun Microsystem's 3456-port InfiniBand Magnum switch. Prof. Duato led the Advanced Technology Group in the HyperTransport Consortium, and was the main contributor to the High Node Count HyperTransport Specification 1.0. He also led the development of rCUDA, which enables remote virtualized access to GP-GPU accelerators using a CUDA interface. Prof. Duato is the first author of the book "Interconnection Networks: An Engineering Approach". He also served as a member of the editorial boards of IEEE Transactions on Parallel and Distributed Systems, IEEE Transactions on Computers, and IEEE Computer Architecture Letters. Prof. Duato was awarded with the National Research Prize in 2009 and the “Rey Jaime I” Prize in 2006. He is a member of the Spanish Royal Academy of Sciences.