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We present Timestamp Order Preserving (TOP), a replicated state machine (RSM) protocol that exploits the synchrony of networks to provide high performance. TOP uses physical timestamp of synchronized clock as a consistent total order to achieve consensus. It keeps estimating the bounds of network latency and offset of synchronized clock to deduce the commit time for each operation. It adopts speculative...
In this paper, the basic methods of routing organization in software-configurable network are considered. The efficiency of the implementation of routing SDN networks are evaluated using a specially designed setting — delays in the routing domain. Evaluates the effectiveness of routing under various principles of organization SDN-Controller and the various protocols for implementing an interface between...
A network of drone cameras can be deployed to cover live events, such as high-action sports game played on a large field, but managing networked drone cameras in real-time is challenging. Distributed approaches yield suboptimal solutions from lack of coordination but coordination with a centralized controller incurs round-trip latencies of several hundreds of milliseconds over a wireless channel....
A lack of energy proportionality, low resource utilization, and interference in virtualized infrastructure make the cloud a challenging target environment for improving energy efficiency. In this paper we present OptiBook, a system that improves energy proportionality and/or resource utilization to optimize performance and energy efficiency. OptiBook shares servers between latency-sensitive services...
Containers have been used in many applications for isolation purposes due to the lightweight, scalable and highly portable properties. However, to apply containers in virtual network functions (VNFs) faces a big challenge because high-performance VNFs often generate frequent communication workloads among containers while the container communications are generally not efficient. Compared with hardware...
Deployed in various distributed storage systems, erasure coding has demonstrated its advantages of low storage overhead and high failure tolerance. Typically in an erasure-coded distributed storage system, systematic maximum distance seperable (MDS) codes are chosen since the optimal storage overhead can be achieved and meanwhile data can be read directly without decoding operations. However, data...
NAT gateway is an important network system in today's IPv4 network when translating a private IPv4 address to a public address. However, traditional NAT system based on Linux Netfilter cannot achieve high network throughput to meet modern requirements such as data centers. To address this challenge, we improve the network performance of NAT system by three ways. First, we leverage DPDK to enable polling...
Network Function Virtualization (NFV) brings agility and flexibility delivering network services with cost efficiency to network operators. As an emerging technology, it also presents several challenges, among them, ensuring high performance for virtualized network functions, based on software implementation and running on standard IT servers, instead of custom hardware appliances. In this article,...
Long-tail latency of web-facing applications continues to be a serious problem. Most of the previously published research addresses two classes of long latency problems: uneven workloads such as web search, and resource saturation in single nodes. We describe an experimental study of a third class of long tail latency problemsthat are specific to distributed systems: Cross-Tier Queue Overflow (CTQO)...
State machine replication is a fundamental approach to high availability. Despite the vast literature on the topic, relatively few studies have considered the issues involved in recovering faulty replicas. Recovering a replica requires (a) retrieving and installing an up-to-date replica checkpoint, and (b) restoring and re-executing the log of commands not reflected in the checkpoint. Parallel techniques...
Scaling web applications such as e-commerce in cloud by adding or removing servers in the system is an important practice to handle workload variations, with the goal of achieving both high quality of service (QoS) and high resource efficiency. Through extensive scaling experiments of an n-tier application benchmark (RUBBoS), we have observed that scaling only hardware resources without appropriate...
In multi-tier cloud service systems, performance evaluation relies on numerous experiments in order to collect key metrics such as resources usage. The approach may result in highly time-consuming in practice. In this paper, we propose an automated framework for performance tracking, data management and analysis to minimize human intervention in multi-tier cloud service systems. The framework support...
Elasticity actions in NoSQL data stores move large amounts of data over the network to take advantage of new resources. Here we propose incremental elasticity, a new mechanism for scheduling data transfers to a joining server, leading to smoother elasticity actions with a reduced performance impact.
Most large popular web applications, like Facebook and Twitter, have been relying on large amounts of in-memory storage to cache data and offer a low response time. As the main memory capacity of clusters and clouds increases, it becomes possible to keep most of the data in the main memory. This motivates the introduction of in-memory storage systems. While prior work has focused on how to exploit...
Replication is a common technique used to design reliable distributed systems by masking defective components. To cope with the requirements of modern Internet applications, replication protocols must allow for throughput scalability and dynamic reconfiguration, that is, on-demand replacement or provisioning of system resources. This paper describes Elastic Paxos, a new dynamic atomic multicast protocol...
LSM-tree has been widely used in data management production systems for write-intensive workloads. However, as read and write workloads co-exist under LSM-tree, data accesses can experience long latency and low throughput due to the interferences to buffer caching from the compaction, a major and frequent operation in LSM-tree. After a compaction, the existing data blocks are reorganized and written...
We present a quality-selection policy for Quality of Experience (QoE) demanding video streaming in wireless networks. The proposed policy predicts the TCP throughput and adapts video segment requests in order to assure high QoE by taking into account the client buffer level. We introduce the concept of Affordable delivery Time (AT) and we design a buffer-based algorithm, hereafter referred to as Buffer-based...
Applications are typically offered a single, generic option for end-to-end transport, which most commonly consists of the particular flavor of TCP that runs in the server host. This arrangement does not suit well the diversity of the requirements that individual applications pose on network metrics like throughput and delay. Link-Coupled TCP (LCTCP) is a new transport solution that leverages the architectural...
In this paper we present the first cross-layer analysis of wireless LANs operating under downlink multi-user MIMO (MU-MIMO), considering the fundamental role played by closed-loop (TCP) traffic. In particular, we consider an 802.11ac scenario in which the access point transmits on the downlink via MU-MIMO, whereas stations must employ single-user transmissions on the uplink. With the help of analytical...
Flow completion times (FCTs) are critical for many cloud applications. To minimize the average FCT, recent transport designs, such as pFabric, PASE, and PIAS, approximate the Shortest Remaining Time First (SRTF) scheduling. A common, implicit assumption of these solutions is that the remaining time is only determined by the remaining flow size. However, this assumption does not hold in many real-world...
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