User-directed routing: from theory, towards practice

User-directed routing technologies - that is, systems in which users choose their own routes through a communications network - have generated considerable interest in recent years. Despite their numerous theoretical advantages, ISPs have so far resisted these technologies, even as users have learned to capture some routing power through overlay networks. This study responds to this disconnect between theory and practice by asking how user-directed routing would affect three prominent objectives of network operators: maintaining control over the network, earning profits, and keeping inner details of the network secret. Contrary to the modern theme in routing proposals, we argue that user-directed routing is not fundamentally incompatible with ISP-control, as long as a flexible pricing system is in place. Instead - and under surprisingly general assumptions - an ISP can use prices on the open market to induce any feasible traffic pattern. Moreover, we argue that the market-based approach maximizes welfare for any given traffic pattern. In general, our model does not guarantee whether an ISP will earn more money under user-directed routing. Nevertheless, we provide some intuition to suggest why a typical ISP may expect higher profits. Finally, we suggest that giving routing power to users conflicts with an ISP's desire for secrecy. At the same time, widespread adoption of user-directed routing, perhaps promoted through regulation, may facilitate a transparent and civil industry, to the benefit of many ISPs.