Techniques are described for updating resources provided to a user device, using subscription based polling. A layer to be etched is applied over the structure and within the trench. In response to an instruction executed at a first privilege level, first configuration data can be set for controlling performance monitoring by a first subset of performance monitoring circuits. Similarly, the inventive network scanner, server systems and communication protocols provide improved ways to perform large file transfers and to manage bandwidth to minimize problems associated with uploadingdownloading large files as attachments tofrom email servers and for enabling user control over VoIP quality during file transmission sessions. If a communication system supports variable carrier bandwidth channels, the narrow channel capacity can be divided among adjacent cells to provide higher re-use.