Adaptive bandwidth allocation for Non-Reserved traffic over high speed transmission links of a digital network is operated through regulation of data packet transfers over network nodes/ports including input/output adapters connected through a switching device. A network node is assigned with a Control Point computing devise (CP) storing a Topology Data Base containing an image of the network. This Data Base is periodically and at call set up updated by Topology Data Base Update messages (TDUs) including an Explicit Rate parameter for link l indicating the current available bandwidth on link l, and a parameter NNRl indicating the number of Non-Reserved connections on link l. This information are used within each Adapter to periodically regulate the transmission bandwidth assigned to each Non-Reserved traffic connection within the network. To that end, each adapter is provided with an Access Control Function device for each attached connection (data source) and a Connection Agent (CA) getting, on request, required current link informations from the attached Topology Data Base.