1 Mbps is the bare minimum, and it needs to be 100% stable; 3-5 Mbps put you in a more comfortable zone.
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Not to mention if anything else at all touches that network, the bandwidth is going to be taken below that 1 mb/s. Also, that 16/1 is advertised. I doubt that is what is actually there. Playing with the absolute minimum as an advertised bandwidth will just never work.