Abstract: In recent years, with the rapid development of computer networks, people increasingly rely on computer networks to obtain information. However, ubiquitous applications are deployed over the wide area networks (WANs), which have shown low transport efficiency due to the natural characteristics of WANs such as high latency and high packet loss rate. WANs optimization, also known as WANs acceleration, which aims to accelerate a broad range of applications and protocols over WANs, has become a hot topic in both academia and industry. Based on the in-depth study of the current WANs optimization techniques from different aspects that cause the WANs performance degradation, a survey is presented on the state of the art of WANs optimization or WANs acceleration techniques from the networking point of view including data optimization and protocol optimization. Data optimization also includes data compression, data caching, data pre-fetching and data de-duplication, while protocol optimization is depicted with transport layer optimization and application-layer protocol optimization. Meanwhile, how these acceleration techniques can improve application performance, mitigate the impact of latency and loss, and minimize bandwidth consumption is also illustrated. In addition, widely deployed WANs acceleration products incorporating major WANs optimization techniques are discussed. Finally, a conclusion and some perspectives are given.