Mechanism-driven model (MDM) plays an important role for time-varying thermal error (TVTE) compensation. For complex working conditions of machine tools, it is needed to ensure that the mechanism-driven model is always accurate in long time. Therefore, the online evolutionary strategy (OES) for MDM was proposed. The model accuracy can be recognized based on the consistency between the calculated value and the measured value of the intermediate dependent variable. The parameters can be updated online. Furthermore, the mechanism-driven model was established based on the OES. The update effect of the model parameters was verified. The compensation accuracy of Model 1 is degraded from 11.8μm to 18.6μm, and Model 2 is degraded from 11.8μm to 14.6μm. After online evolution, the compensation accuracy is improved to 12.5μm for Model 1 and to 10.4μm for Model 2. It is shown that the OES can effectively correct the calculation accuracy of TVTE model.

In recent years, large enterprises (e.g., Google, Alibaba, etc.) have been building and deploying their wide-area routers based on shallow-buffered switching chips. However, with legacy reactive transport (e.g., TCP Cubic), shallow buffer can easily get overwhelmed by large BDP wide-area traffic, leading to high packet losses and degraded throughput. To address it, we ask: can we design a transport to simultaneously achieve high throughput and low loss for shallow-buffered WAN?We answer this question affirmatively by employing proactive congestion control (PCC). However, two issues exist for existing PCC to work on WAN. Firstly, wide-area traffics have diverse RTTs, leading to what we called imperfect scheduling issue (e.g., data crash in time). Secondly, there is one RTT delay for credits to trigger data sending, which may degrade network performance. Therefore, we propose a novel PCC design - FlashPass. To address the first issue, FlashPass adopts sender-driven emulation process with send time calibration to avoid the data packet crash. To address the second issue, FLASHPASS enables early data transmission in the starting phase, and incorporates an over-provisioning with selective dropping mechanism for efficient credit allocation in the finishing phase. Our evaluation with production workload demonstrates that FlashPass reduces the overall flow completion times of TCP Cubic and ExpressPass by up to 32% and 11.4%, and the 99-th tail completion times of small flows by up to 49.5% and 38%, respectively.

We present an Internet-scale network topology information (NTI) service named WIND for localizing P2P traffic. Central to WIND are the two simple ideas: 1) obtaining NTI directly from routing infrastructures, and 2) leveraging existing, widely deployed DNS caches for NTI delivery. WIND fulfills the fidelity, flexibility and scalability requirement of an effective NTI service. WIND is deployed in CERNET. We conduct extensive trace-driven emulations on PlanetLab. Experimental results confirm the effectiveness of the WIND service.

Broadcatching is a promising mechanism to improve the experience of BitTorrent users by automatically downloading files advertised through RSS feeds. However, though widely used, the mechanism itself has not been well studied. In this paper, we conducted extensive experiments on PlanetLab to evaluate the performance of Broadcatching under different typical scenarios. The results demonstrated the effectiveness of the broadcatching: it reduces the average completion time and downloading failure ratio. It also improves the overall fairness of the system: the subscribers are encouraged to share more while downloading faster, which results in the increased share ratio. Our study is the first work to systematically evaluate the benefit of broadcatching and sheds lights on how to improve performance of BitTorrrent by manipulating peer's behavior like Broadcatching.