Network calculus for parallel processing

In this note, we present preliminary results on the use of "network calculus" for parallel processing systems, specifically MapReduce

A general framework for handling commitment in online throughput maximization

We study a fundamental online job admission problem where jobs with deadlines arrive online over time at their release dates, and the task is to determine a preemptive single-server schedule which maximizes the number of jobs that complete on time. To circumvent known impossibility results, we make a standard slackness assumption by which the feasible time window for scheduling a job is at least $1+\varepsilon$ times its processing time, for some $\varepsilon>0$. We quantify the impact that different provider commitment requirements have on the performance of online algorithms. Our main contribution is one universal algorithmic framework for online job admission both with and without commitments. Without commitment, our algorithm with a competitive ratio of $O(1/\varepsilon)$ is the best possible (deterministic) for this problem. For commitment models, we give the first non-trivial performance bounds. If the commitment decisions must be made before a job's slack becomes less than a $\delta$-fraction of its size, we prove a competitive ratio of $O(\varepsilon/((\varepsilon-\delta)\delta^2))$, for $0<\delta<\varepsilon$. When a provider must commit upon starting a job, our bound is $O(1/\varepsilon^2)$. Finally, we observe that for scheduling with commitment the restriction to the `unweighted' throughput model is essential; if jobs have individual weights, we rule out competitive deterministic algorithms

An Average-Case Analysis for Rate-Monotonic Multiprocessor Real-time Scheduling

We introduce the "First Fit Matching Periods" algorithm for static-priority multiprocessor scheduling of periodic tasks with implicit deadlines and show that it yields asymptotically optimal processor assignments if utilization values are chosen uniformly at random. More precisely we prove that the expected waste is upper bounded by O(n^(3/4) * (log n)^(3/8)). Here the waste denotes the ratio of idle times, cumulated over all processors and n gives the number of tasks. The algorithm can be implemented to run in time O(n log n) and even in the worst case, an asymptotic approximation ratio of 2 is guaranteed. Experiments yield an expected waste proportional to n^0.70, indicating that the above upper bound on the expected waste is almost tight

Distributing key updates in secure dynamic groups

Abstract. We focus on the problem of distributing key updates in secure dynamic groups. Due to changes in group membership, the group controller needs to change and distribute the keys used for ensuring encryption. However, in the current key management algorithms the group controller broadcasts these key updates even if only a subset of users need them. In this paper, we describe a key distribution algorithm for distributing keys to only those users who need them. Towards this end, we propose a descendent tracking scheme. Using our scheme, a node forwards an encrypted key update only if it believes that there are descendents who know the encrypting key. We also describe an identifier assignment algorithm which assigns closer logical identifiers to users who are physically close in the multicast tree. We show that our identifier assignment algorithm further improves the performance of our key distribution algorithm as well as that of a previous solution. Our simulation results show that a bandwidth reduction of upto 55 % is achieved by our algorithms

Workshop report: ACM SIGCOMM workshop on computer networking: Curriculum designs and educational challenges

This year’s annual ACM Sigcomm Conference featured a one-day workshop entitled &amp;quot;Computer Networking: Curriculum Designs and Educational Challenges. &amp;quot; The goal of the workshop was to bring together faculty from a broad spectrum of four-year colleges and universities, industry engineers and scientists, and others with an interest in networking education to discuss curriculum design and teaching practices in the field of computer networks. Eighty-nine people participated in this first-ever workshop focused solely on the educational aspects of the networking field. Workshop activities included panels on undergraduate curricula, laboratory-based courses, and graduate curricula. This report summarizes the workshop’s presentations, discussions, and findings, as well as plans for future education-related activities