  The problem of packet scheduling for traffic streams with target outflow
profiles traversing input queued switches is formulated in this paper. Target
outflow profiles specify the desirable inter-departure times of packets leaving
the switch from each traffic stream. The goal of the switch scheduler is to
dynamically select service configurations of the switch, so that actual outflow
streams ("pulled" through the switch) adhere to their desired target profiles
as accurately as possible. Dynamic service controls (schedules) are developed
to minimize deviation of actual outflow streams from their targets and suppress
stream "distortion". Using appropriately selected subsets of service
configurations of the switch, efficient schedules are designed, which deliver
high performance at relatively low complexity. Some of these schedules are
provably shown to achieve 100% pull-throughput. Moreover, simulations
demonstrate that for even substantial contention of streams through the switch,
due to stringent/intense target outflow profiles, the proposed schedules
achieve closely their target profiles and suppress stream distortion. The
switch model investigated here deviates from the classical switching paradigm.
In the latter, the goal of packet scheduling is primarily to "push" as much
traffic load through the switch as possible, while controlling delay to
traverse the switch and keeping congestion/backlogs from exploding. In the
model presented here, however, the goal of packet scheduling is to "pull"
traffic streams through the switch, maintaining desirable (target) outflow
profiles.
