— Operators need routers to provide service guarantees such as guaranteed flow rates and fairness among flows, so as to support real-time traffic and traffic engineering. However, current centralized input-queued router architectures cannot scale to fast line rates while providing these service guarantees. On the other hand, while load-balanced switch architectures that rely on two identical stages of fixed configuration switches appear to be an effective way to scale Internet routers to very high capacities, there is currently no practical and scalable solution for providing service guarantees in these architectures. In this paper, we introduce the interleaved matching switch (IMS) architecture, which relies on a novel approach to provide service guarantees using load-balanced switches. The approach is based on emulating a Birkhoff-von Neumann switch with a loadbalanced switch architecture and is applicable to any admissible traffic. In cases where fixed frame sizes are appl...