To Queue or Not to Queue: When Queueing is Better Than Timesharing in a Distributed System

We examine the question of whether to employ the first-come-first-served (FCFS) discipline or the processor-sharing (PS) discipline at the hosts in a distributed server system. We are interested in the case in which service times are drawn from a heavy-tailed distribution, and so have very high variability. Traditional wisdom when task sizes are highly variable would prefer the PS discipline, because it allows small tasks to avoid being delayed behind large tasks in a queue. However, we show that system performance can actually be significantly better under FCFS queueing, if each task is assigned to a host based on the task's size. By task assignment, we mean an algorithm that inspects incoming tasks and assigns them to hosts for service. The particular task assignment policy we propose is called SITA-E: Size Interval Task Assignment with Equal Load. Surprisingly, under SITA-E, FCFS queueing typically outperforms the PS discipline by a factor of about two, as measured by mean waiting time and mean slowdown (waiting time of task divided by its service time). We compare the FCFS/SITA-E policy to the processor-sharing case analytically; in addition we compare it to a number of other policies in simulation. We show that the benefits of SITA-E are present even in small-scale distributed systems (four or more hosts). Furthermore, SITA-E is a static policy that does not incorporate feedback knowledge of the state of the hosts, which allows for a simple and scalable implementation.

A Catechumenate for the Korean Methodist Church: Ressourcement, Formation and a Response to Secularism and Korean Traditional Religions

Research by Korean sociologists of religion indicates that Korean Protestantism has lost much of the spiritual vitality of preceding generations and that it increasingly shows the influences of Korean shamanism, Neo-Confucianism, and Western secularism and consumerism. Suggestions in the areas of homiletics and Christian social ethics have been offered to help steer the Korean Protestant churches away from these worldviews toward a more biblically-based course. Drawing upon and expanding these earlier studies and proposals, the current work recommends another method for developing a biblically-based, spiritually-revitalized, baptismally-shaped and ministry-committed Protestantism in Korea: a pre-baptismal adult catechumenate, in this case one designed for the context of the Korean Methodist Church. In order to produce a renewed catechumenal structure for Korean Methodism, adult catechumenal processes as well as baptismal theologies and rites are examined and analyzed from three principal sources: the first five centuries of the Christian church, and especially the mystagogical literature of the fourth century; the Roman Catholic Rite of Christian Initiation of Adults developed after the Second Vatican Council; and the United Methodist Church in the United States, both texts officially authorized by the denomination's General Conference and unofficial materials, among them resources for an adult catechumenate in the Come to the Waters series. In addition, previous and current practices of preparation for baptism in the Korean Methodist Church are identified and critiqued. From these findings a set of principles is put forward that guide the proposed catechumenal structure.

Fine-Grained Layered Multicast

Traditional approaches to receiver-driven layered multicast have advocated the benefits of cumulative layering, which can enable coarse-grained congestion control that complies with TCP-friendliness equations over large time scales. In this paper, we quantify the costs and benefits of using non-cumulative layering and present a new, scalable multicast congestion control scheme which provides a fine-grained approximation to the behavior of TCP additive increase/multiplicative decrease (AIMD). In contrast to the conventional wisdom, we demonstrate that fine-grained rate adjustment can be achieved with only modest increases in the number of layers and aggregate bandwidth consumption, while using only a small constant number of control messages to perform either additive increase or multiplicative decrease.