Method and apparatus are disclosed for constrained dynamic path selection among multiple available communication interfaces. In some embodiments selection logic is operatively coupled with a number of link-layer interfaces to select a set of link-layer interfaces that satisfy a set of congestion constraint conditions. Metric logic is operatively coupled with the link-layer interfaces to calculate a metric value for each link-layer interface in the set. Switch logic is operatively coupled with the selection logic and metric logic to assign a data stream a link-layer interface in the set of interfaces according to its metric value to optimize communication performance.