CR Switch: A Load-Balanced Switch with Contention and Reservation

Load-balanced switches have received a great deal of attention recently as they are much more scalable than other existing switch architectures in the literature. However, as there exist multiple paths for flows of packets to traverse through load-balanced switches, packets in such switches may be delivered out of order. In this paper, we propose a new switch architecture, called the CR switch, that not only delivers packets in order but also guarantees 100% throughput. The key idea, as in a multiple access channel, is to operate the CR switch in two modes: (i) the contention mode in light traffic and (ii) the reservation mode in heavy traffic. To do this, we invent a new buffer management scheme, called I-VOQ (virtual output queue with insertion). With the I-VOQ scheme, we give rigorous mathematical proofs for 100% throughput and in order packet delivery of the CR switch. By computer simulations, we also demonstrate that the average packet delay of the CR switch is considerably lower than other schemes in the literature, including the uniform frame spreading scheme (Keslassy et al., 2003), the padded frame scheme (Jaramillo et al., 2006) and the mailbox switch (Chang et al., 2004).