1. A method of providing network access across a shared communications medium between competing users pursuant to service level agreements (SLAs) of the users, comprising the steps of: (a) monitoring network access usage by each user during a time interval; (b) comparing said monitored network access usage by each user with a predetermined threshold value; and (c) soliciting a user to modify the user's SLA if the user's monitored network access usage varies from the predetermined value by a predetermined tolerance.