Asaf Cidon

Flashback: decoupled lightweight wireless control

Unlike their cellular counterparts, Wi-Fi networks do not have the luxury of a dedicated control plane that is decoupled from the data plane. Consequently, Wi-Fi struggles to provide many of the capabilities that are taken for granted in cellular networks, including efficient and fair resource allocation, QoS and handoffs. The reason for the lack of a control plane with designated spectrum is that it would impose significant overhead. This is at odds with Wi-Fis goal of providing a simple, plug-and-play network. In this paper we present Flashback, a novel technique that provides a decoupled low overhead control plane for wireless networks that retains the simplicity of Wi-Fis distributed asynchronous operation. Flashback allows nodes to reliably send short control messages concurrently with data transmissions, while ensuring that data packets are decoded correctly without harming throughput. We utilize Flashbacks novel messaging capability to design, implement and experimentally evaluate a reliable control plane for Wi-Fi with rates from 175Kbps to 400Kbps depending on the environment. Moreover, to demonstrate its broad applicability, we design and implement a novel resource allocation mechanism that utilizes Flashback to provide efficient, QoS-aware and fair medium access, while eliminating control overheads including data plane contention, RTS/CTS and random back offs.

Reducing DRAM footprint with NVM in Facebook

Popular SSD-based key-value stores consume a large amount of DRAM in order to provide high-performance database operations. However, DRAM can be expensive for data center providers, especially given recent global supply shortages that have resulted in increasing DRAM costs. In this work, we design a key-value store, MyNVM, which leverages an NVM block device to reduce DRAM usage, and to reduce the total cost of ownership, while providing comparable latency and queries-per-second (QPS) as MyRocks on a server with a much larger amount of DRAM. Replacing DRAM with NVM introduces several challenges. In particular, NVM has limited read bandwidth, and it wears out quickly under a high write bandwidth. We design novel solutions to these challenges, including using small block sizes with a partitioned index, aligning blocks post-compression to reduce read bandwidth, utilizing dictionary compression, implementing an admission control policy for which objects get cached in NVM to control its durability, as well as replacing interrupts with a hybrid polling mechanism. We implemented MyNVM and measured its performance in Facebooks production environment. Our implementation reduces the size of the DRAM cache from 96 GB to 16 GB, and incurs a negligible impact on latency and queries-per-second compared to MyRocks. Finally, to the best of our knowledge, this is the first study on the usage of NVM devices in a commercial data center environment.

An interview with Peter Levine: academics as founders, teaching entrepreneurship

Peter Levine, general partner at Andreessen Horowitz and lecturer at Stanford, shares his insights on how startups should assemble their initial team and create their first product.

An interview with Mendel Rosenblum

The co-founder of VMware and Associate Professor of Computer Science at Stanford explains how an academic research project evolved into a commercial idea.