Web caching is an important technology for reducing Internet access latency, alleviating network traffic, and spreading server load. An important issue that affects the performance of web caching is caching architecture, in which several caches are usually federated for making caches cooperate on a large scale and effectively increase the cache population. Transparent data replication is such a caching architecture, which has shown to be easy to manage and have good system scalability. In this paper, we present an survey of state-of-the-art techniques of cache/proxy placement for transparent data replication.