Abstract The demand for bandwidth contracts over networks has recently been growing rapidly. Moreover, due to increased competition among providers, customized short-term bandwidth contracts are now preferred by users to static, long-term contracts of the past. To this end, auctions appear to be a proper trading mechanism. When purchasing bandwidth over a path of a network, it is only meaningful for a user to reserve the same quantity at all the constituent links. We have developed a simple, yet efficient auction for allocating bandwidth on a network basis to users who wish to utilize it for the same time period. This mechanism (referred to as MIDAS) consists of a set of simultaneous multi-unit Dutch (i.e. descending-price) auctions, one per link of the network. In order to win bandwidth over a certain path, it suffices for a user to simultaneously bid for the quantity desired at all relevant auctions. Thus, instant allocation of bandwidth is attained. An important feature of our approach is that prices at the various links are reduced at different rates, so that prices reflect the demand exhibited so far for each link. We have evaluated experimentally two price reduction policies, in terms of the social welfare associated with the resulting allocation, and argue (both theoretically and by means of experimental results) that it is indeed efficient to introduce such rules rather than reduce all prices at the same rate. We have also briefly addressed the issue of incentive compatible pricing.