With high gigabit port densities gigabit sfp 10 gigabit sfp support and advanced software solutions these switches can act as either departmental access layer devices or aggregation switches to form a multilevel network structured with backbone and centralised high speed servers service providers can take advantage of the high sfp density switch such as dgs 3420 28sc to structure the aggregation of fiber to the building fttb networks that are extended to the subscribers sites