Achieving 100% throughput in an input-queued switch

Abstract

-It is well known that head-of-line (HOL) blocking limits the throughput of an input-queued switch with FIFO queues. Under certain conditions, the throughput can be shown to be limited to approximately 58%. It is also known that if non-FIFO queueing policies are used, the throughput can be increased. However, it has not been previously shown that if a suitable queueing policy and scheduling algorithm are used then it is possible to achieve 100% throughput for all independent arrival processes. In this paper we prove this to be the case using a simple linear programming argument and quadratic Lyapunov function. In particular, we assume that each input maintains a separate FIFO queue for each output and that the switch is scheduled using a maximum weight bipartite matching algorithm. We introduce two maximum weight matching algorithms: LQF and OCF. Both algorithms achieve 100% throughput for all independent arrival processes. LQF favors queues with larger occupancy, ensuring that larger queues will eventually be served. However, we find that LQF can lead to the permanent starvation of short queues. OCF overcomes this limitation by favoring cells with large waiting times.

Spatial inefficiency of MaxWeight scheduling

“…matchings) may be simultaneously connected because of compatibility constraints, see for instance McKeown et al [13], [14]. The book of Meyn [15] contains extensive background material on MaxWeight policies.…”

Wireless Scheduling Design for Optimizing Both Service Regularity and Mean Delay in Heavy-Traffic Regimes

“…We are ready to provide an upper bound on the first term in the LHS of (15). Noting the fact that the amount of unused service in one time-slot at each link cannot be greater than the maximum channel rate , i.e., , we have (17) where the last step utilizes inequality (16). Next, we focus on the second term in the LHS of (15).…”

“…Yet, both the time-varying nature of wireless channels and the scheduling policy significantly affect the regularity of the received data of each mobile user. The traditional scheduling policies aiming to maximize the system throughput (e.g., [10], [17], and [22]) or provide various fairness guarantees (e.g., [3], [16], [18], and [21]) at the base station side do not take users' experience into account and thus lead to the high irregularity of the received data of mobile users.…”

Joint Static and Dynamic Traffic Scheduling in Data Center Networks

“…In a simple switching network, a router or switch is designed to operate in a chassis or rack, and can employ a centralized scheduler to compute a match between ingress and egress ports in each transmission time-slot [11]. In a more generalized network, a centralized scheduler can perform path selection and bandwidth allocation for each traffic flow [12].…”