A stepped-frequency chirped waveform improves SAR groundmapping for the following reasons. A packet flow intended for a first destination is received into the cache system. To enable the use of this method for glass ducts of varying diameters, the glass duct can be retained in a fixed position during cutting, while a cutting member, as well as a counterpressure surface for the cutting member, are moved all round the glass duct. Each method in the plurality of grouped methods is executed by a particular cluster member in the server cluster.