A method for establishing an authenticated network connection in a packet-switched network with an electronic equipment, the method including transmitting a request from an electronic equipment through a packet-switched network connection to an authentication server. A tube support receives open tube ends. The contaminants combine with the sacrificial layer and are removed by etching away the sacrificial layer. After assigning the clients to the group, at least one of the clients can be capable of downloading content from, or uploading content to, the server based upon the group. The difference in synchronization can be determined in various ways such as computing a phase difference andor amplitude difference between the accelerometer signals.