Search

To fulfill the low latency requirements of today's applications, deployment of RDMA in datacenters has become prevalent over the recent years. However, the in-order delivery requirement of RDMAs prevents them from leveraging powerful techniques that help improve the performance of datacenters, ranging from fine-grained load balancers to throughput-optimal expander topologies. We demonstrate experimentally that these techniques significantly deteriorate the performance in an RDMA network because they induce packet reordering. Furthermore, lifting the in-order delivery constraint enhances the flexibility of RDMA networks and enables them to employ these performance-enhancing techniques. To realize this, we propose an ordering layer, Eunomia, to equip RDMA NICs to handle packet reordering. Eunomia employs a hybrid-dynamic bitmap structure that efficiently uses the limited on-chip memory with the help of a customized memory controller and handles high degrees of packet reordering. We evaluate the feasibility of Eunomia through an FPGA-based implementation and its performance through large-scale simulations. We show that Eunomia enables a wide range of applications in RDMA datacenter networks, such as fine-grained load balancers which improve performance by reducing average flow completion times by 85% and 52% compared to ECMP and Conweave, respectively, or employment of RDMA in expander topologies like Jellyfish which allows up to 60% lower flow completion times and higher throughput gains compared to Fat tree.

The security of cyber-physical systems, from self-driving cars to medical devices, depends on their underlying multi-hop wireless networks. Yet, the lack of trusted central infrastructures and limited nodes' resources make securing these networks challenging. Recent works on key pre-distribution schemes, where nodes communicate over encrypted overlay paths, provide an appealing solution because of their distributed, computationally light-weight nature. Alas, these schemes share a glaring security vulnerability: the two ends of every overlay link can decrypt---and potentially modify and alter---the message. Plus, the longer overlay paths impose traffic overhead and increase latency. We present a novel routing mechanism, KPsec, to address these issues. KPsec deploys multiple disjoint paths and an initial key-exchange phase to secure end-to-end communications. After the initial key-exchange phase, traffic in KPsec follows the shortest paths and, in contrast to key pre-distribution schemes, intermediate nodes cannot decrypt it. We measure the security and performance of KPsec as well as three state-of-the-art key pre-distribution schemes using a real 10-node testbed and large-scale simulations. Our experiments show that, in addition to its security benefits, KPsec results in $5-15\%$ improvement in network throughput, up to $75\%$ reduction in latency, and an order of magnitude reduction in energy consumption., Comment: 20 pages, 10 figures, 3 tables, testbed experiment, exhaustive performance evaluation