The web services architecture came as answers to the search for interoperability among applications. In recent years there has been a growing interest in deploying on the Internet applications with high availability and reliability requirements. However, the technologies associated with this architecture still do not deliver adequate support to this requirement. The model proposed in this article is located in this context and provides a new layer of software that acts as a proxy between client requests and service delivery by providers. The main objective is to ensure client transparent fault tolerance by means of the active replication technique. This model supports the following faults: value, omission and stops. This paper describes the features and outcomes obtained through the implementation of this model.