Macbook Pro using all the bandwidth
nsurlsessiond is used by other software to make requests on their behalf, the most common source of large amounts of data being transfered with it on workstations and end-user devices is iCloud Photo Library and iCloud Drive. 

You can watch for filesystem activity in ~/Library/Caches/CloudKit if photo sync doesn't seem to be the source. It is possible to have a condition where sync operations with iCloud Drive don't reconcile as expected and your workstation will be re-fetching data — you will see evidence of this in logs for bird(8) for the user.