Robustness to Inflated Subscription in Multicast Congestion Control

Group subscription is a useful mechanism for multicast congestion control: RLM, RLC, FLID-DL, and WEBRC form a promising line of multi-group protocols where receivers provide no feedback to the sender but control congestion via group membership regulation. Unfortunately, the group subscription mechanism also o#ers receivers an opportunity to elicit self-beneficial bandwidth allocations. In particular, a misbehaving receiver can ignore guidelines for group subscription and choose an unfairly high subscription level in a multi-group multicast session. This poses a serious threat to fairness of bandwidth allocation. In this paper, we present the first solution for the problem of inflated subscription. Our design guards access to multicast groups with dynamic keys and consists of two independent components: DELTA (Distribution of ELigibility To Access) -- a novel method for in-band distribution of group keys to receivers that are eligible to access the groups according to the congestion control protocol, and SIGMA (Secure Internet Group Management Architecture) -- a generic architecture for key-based group access at edge routers

IS PREVENTION ALWAYS BETTER? A CASE OF IT SERVICE MANAGEMENT

Information Technology Infrastructure Library (ITIL), a framework for IT Service Management (ITSM), emphasizes the need for an ongoing preventive activity woven into the fabric of enterprise IT of organizations as opposed to a reacting to a specific situation. However, with the increasing focus on cost reduction, it is essential to revisit the trade-off between costs and other primary ITSM objectives such as service availability and quality. With this basic premise, we compare the cost of conducting IT service operations with varying levels of prevention. We modelled the IT service operation processes based on queuing and software reliability theories while assessing the impact of exogenous variables such as initial application maturity, drop rates & monitoring cost. We illustrated that optimum lies between the extremes of complete prevention and reaction. Also, we were able to observe the pronounced impact of staffing stickiness on the results

On the Effectiveness of Buffer in Deterministic Services

We study the utility of buffer at switches in increasing the achievable utilization of a network providing deterministic guarantee. To determine the increase in utilization, we classify packet scheduling algorithms into two classes. Only one of these classes can utilize additional buffers to increase the achievable utilization. We experimentally determine the difference in achievable utilization of these classes. Our experiments demonstrate that contrary to intuition, in most cases, additional buffers do not lead to higher achievable utilization of a network. 1 Introduction Integrated services networks support a diverse set of applications (e.g., data, audio, interactive video, stored video applications). The traffic characteristics as well as Quality of Service (QoS) requirements of these diverse applications vary significantly. To meet the QoS of requirements of the applications, a network has to manage two resources: link bandwidth and packet buffers. While several packet schedulin..

Effairness: A Metric for Congestion Control Evaluation in Dynamic Networks

This paper examines the problem of congestion control evaluation in dynamic networks. We determine a source of deficiencies for existing metrics of congestion control performance -- the existing metrics are defined with respect to ideal allocations that do not represent short-term efficiency and fairness of network usage in dynamic environments. We introduce the concept of an effair allocation, a dynamic ideal allocation that specifies optimal efficiency and fairness at every timescale. This concept has a general applicability; in particular, it applies to networks that provide both unicast and multicast services. Another desirable property of the effair allocation is its dependence on the communication needs and capabilities of applications. We design an algorithm that accounts for network delays and computes the effair allocation as a series of static ideal allocations. Using the notion of effair allocation as a foundation, we define a new metric of effairness that shows how closely the actual delivery times match the delivery times under the effair allocation.