Track: Tracerouting in SDN networks with arbitrary network functions

The centralization of control plane in Software defined networking (SDN) creates a paramount challenge on troubleshooting the network as packets are ultimately forwarded by distributed data planes. Existing path tracing tools largely utilize packet tags to probe network paths among SDN-enabled switches. However, network functions (NFs) or middleboxes, whose presence is ubiquitous in today's networks, can drop packets or alter their tags - an action that can collapse the probing mechanism. In addition, sending probing packets through network functions could corrupt their internal states, risking of the correctness of servicing logic (e.g., incorrect load balancing decisions). In this paper, we present a novel troubleshooting tool, Track, for SDN-enabled network with arbitrary NFs. Track can discover the forwarding path including NFs taken by any packets, without changing the forwarding rules in switches and internal states of NFs. We have implemented Track on RYU controller. Our extensive experiment results show that Track can achieve 95.08% and 100% accuracy for discovering forwarding paths with and without NFs respectively, and can efficiently generate traces within 3 milliseconds per hop

Modest BBR: Enabling better fairness for BBR congestion control

As a vital component of TCP, congestion control defines TCP's performance characteristics. Hence, it is important for congestion control to provide high link utilization and low queuing delay. Recent BBR tries to estimate available bottleneck capacity to achieve this goal. However, its aggressiveness characteristics generate a massive amount of packet retransmission which harms loss-based congestion control protocol such as Cubic. In this paper, we first dive into this issue and reveal that the aggressiveness of BBR can degrade the performance of Cubic, as well as the overall Internet transmission. Then we present Modest BBR, a simple yet effective solution based on BBR, by responding to retransmission less aggressively. Through extensive testbed experiments and Mininet simulation, we show Modest BBR can preserve high throughput and short convergence time while improve the overall performance when coexisting with Cubic. For example, Modest BBR gets similar throughput compared to BBR, while it improves 7.1% of the overall throughput and achieves better fairness to loss-based schemes

Delay factors for international engineer-procure-construct (EPC) high-speed rail construction projects

Due to complex projects and diverse risks, schedule delay has always been one of the major problems in high-speed rail construction. Chinese infrastructure companies are the main force of the international market after the Chinese government implemented the One Belt and One Road initiative (OBOR). Currently, more than 10 international engineer-procure-construct high-speed rail (IEPCHSR) projects are being considered or undertaken overseas by Chinese companies. However, delay has severe consequences for the progress of most IEPCHSR projects. The aim of this study is to identify the significant delay factors for IEPCHSR projects. This study was conducted as an exploratory study through literature review and semi-structured interview with seven managers from Chinese IEPCHSR related companies. Result reveals that some delay factors concluded from general international infrastructure projects are also applicable in IEPCHSR projects. In the engineering phase, inappropriate management in design management, inefficient land acquisition, design changes and lack of EPC subsidiary contract management for HSR projects are likely to cause delays. In the procurement phase, improper procurement prepared, under-estimated procurement price, unreliable agency, inefficient logistics in equipment and labour are leading causes. In the construction phase, the significant delay factors are improper construction task planning, inexperienced site supervision, ineffective technical standard management and ineffective continuous progress payment. Further study will analyse their interrelationships with Chinese construction companies using a questionnaire survey and structural equation modelling (SEM) technique. The result from this study should enable the Chinese HSR practitioners to gain a better understanding of the inter-relationships between the different potential delay factors

TCon: A transparent congestion control deployment platform for optimizing WAN transfers

Nowadays, many web services (e.g., cloud storage) are deployed inside datacenters and may trigger transfers to clients through WAN. TCP congestion control is a vital component for improving the performance (e.g., latency) of these services. Considering complex networking environment, the default congestion control algorithms on servers may not always be the most efficient, and new advanced algorithms will be proposed. However, adjusting congestion control algorithm usually requires modification of TCP stacks of servers, which is difficult if not impossible, especially considering different operating systems and configurations on servers. In this paper, we propose TCon, a light-weight, flexible and scalable platform that allows administrators (or operators) to deploy any appropriate congestion control algorithms transparently without making any changes to TCP stacks of servers. We have implemented TCon in Open vSwitch (OVS) and conducted extensive test-bed experiments by transparently deploying BBR congestion control algorithm over TCon. Test-bed results show that the BBR over TCon works effectively and the performance stays close to its native implementation on servers, reducing latency by 12.76% on average

A fine-grained and transparent congestion control enforcement scheme

In practice, a single TCP congestion control is often used to handle all TCP connections on a Web server, e.g., Cubic for Linux by default. Considering complex and ever-changing networking environment, the default congestion control algorithm may not always be the most suitable one. Adjusting congestion control usually to meet different networking scenarios requires modification of servers' TCP stacks. This is difficult, if not impossible, due to various operating systems and different configurations on the servers. In this paper, we propose Mystique, a light-weight and flexible scheme that allows administrators (or operators) to deploy any congestion control schemes transparently without changing existing TCP stacks on servers. We have implemented Mystique in Open vSwitch (OVS) and conducted extensive test-bed experiments in public cloud environments. We have extensively evaluated Mystique and the results have demonstrated that it is able to effectively adapt to varying network conditions, and can always employ the most suitable congestion control for each TCP connection. Mystique can significantly reduce latency by up to 37.8% in comparison with other congestion controls

Mystique: a fine-grained and transparent congestion control enforcement scheme

TCP congestion control is a vital component for the latency of Web services. In practice, a single congestion control mechanism is often used to handle all TCP connections on a Web server, e.g., Cubic for Linux by default. Considering complex and ever-changing networking environment, the default congestion control may not always be the most suitable one. Adjusting congestion control to meet different networking scenarios usually requires modification of TCP stacks on a server. This is difficult, if not impossible, due to various operating system and application configurations on production servers. In this paper, we propose Mystique, a light-weight, flexible, and dynamic congestion control switching scheme that allows network or server administrators to deploy any congestion control schemes transparently without modifying existing TCP stacks on servers. We have implemented Mystique in Open vSwitch (OVS) and conducted extensive testbed experiments in both public and private cloud environments. Experiment results have demonstrated that Mystique is able to effectively adapt to varying network conditions, and can always employ the most suitable congestion control for each TCP connection. More specifically, Mystique can significantly reduce latency by 18.13% on average when compared with individual congestion controls

Additional file 1: Figure S1. of Regulation of pancreatic stellate cell activation by Notch3

Representative western blotting images showing α-SMA, collagen I and fibronectin expression in PaSCs; densitometry analyses of the blots is also shown. 1. MOCK; 2. NC; 3. Notch3 siRNA; 4. LTPA-conditioned medium; 5. LTPA-conditioned medium + Notch3 siRNA. *P < 0.05, **P < 0.01, and ***P < 0.001; Student’s t-test; n = 4. Bars represent mean ± SD. (TIFF 749 kb

The weight system of development indicators of new occupation practitioners in China.

The weight system of development indicators of new occupation practitioners in China.</p

Development Indicators of the new occupation practitioners in China.

Development Indicators of the new occupation practitioners in China.</p

S1 Data -

Owing to the increasingly complex economic environment and difficult employment situation, a large number of new occupations have emerged in China, leading to job diversification. Currently, the overall development status of new occupations in China and the structural characteristics of new occupation practitioners in different cities are still unclear. This study first constructed a development index system for new occupation practitioners from five dimensions (group size, cultural appreciation, salary level, occupation perception, and environmental perception). Relevant data to compare and analyze the development status of new occupation practitioners were derived from the big data mining of China’s mainstream recruitment platforms and the questionnaire survey of new professional practitioners which from four first-tier cities and 15 new first-tier cities in China. The results show that the development level of new occupation practitioners in the four first-tier cities is the highest, and the two new first-tier cities, Chengdu and Hangzhou, have outstanding performance. The cities with the best development level of new occupation practitioners in Eastern, Central, and Western China are Shanghai, Wuhan, and Chengdu, respectively. Most new occupation practitioners in China are confident about the future of their careers. However, more than half of the 19 cities are uncoordinated in the five dimensions of the development of new occupation practitioners, especially those cities with middle development levels. A good policy environment and social environment have not yet been formulated to ensure the sustainable development of new occupation practitioners. Finally, we proposed the following countermeasures and suggestions: (1) Establish a classified database of new occupation talents. (2) Implement a talent industry agglomeration strategy. (3) Pay attention to the coordinated development of new occupation practitioners in cities.</div