downlink read-only property of the
NetworkInformation interface returns the effective bandwidth estimate in megabits per second, rounded to the nearest multiple of 25 kilobits per seconds. This value is based on recently observed application layer throughput across recently active connections, excluding connections made to a private address space. In the absence of recent bandwidth measurement data, the attribute value is determined by the properties of the underlying connection technology.
var downLink = NetworkInformation.downlink
|Network Information API
The definition of 'downlink' in that specification.