Software architecture recovery and restructuring through clustering techniques

Capturing of software architecture is critical for maintenance and evolution. However, existing approaches often are limited only to software architecture recovery in the reverse engineering process. What is needed more is a systematic and effective approach to help the designer to restructure or reengineer an architecture for improvement. This paper presents an quantitative approach based on clustering techniques for software architecture restructuring and reengineering as well as for software architecture recovery. Clustering techniques are built on top of reverse engineering tools. The approach has been applied to several examples at various levels of abstraction. Two case studies are presented in this paper. One is an empirical study of a decoupling effort for a real-time telecommunications system. The other example shows a research potential to enforce the designer to improve an architecture by adopting a design pattern based on the clustering results. 1.1 Keywords Architecture recovery, restructuring, evolution, clustering, patterns 2

Delay Optimal Server Assignment to Symmetric Parallel Queues with Random Connectivities

In this paper, we investigate the problem of assignment of $K$ identical servers to a set of $N$ parallel queues in a time slotted queueing system. The connectivity of each queue to each server is randomly changing with time; each server can serve at most one queue and each queue can be served by at most one server per time slot. Such queueing systems were widely applied in modeling the scheduling (or resource allocation) problem in wireless networks. It has been previously proven that Maximum Weighted Matching (MWM) is a throughput optimal server assignment policy for such queueing systems. In this paper, we prove that for a symmetric system with i.i.d. Bernoulli packet arrivals and connectivities, MWM minimizes, in stochastic ordering sense, a broad range of cost functions of the queue lengths including total queue occupancy (or equivalently average queueing delay).Comment: 6 pages, 4 figures, Proc. IEEE CDC-ECC 201

An Early Benchmark of Quality of Experience Between HTTP/2 and HTTP/3 using Lighthouse

Google's QUIC (GQUIC) is an emerging transport protocol designed to reduce HTTP latency. Deployed across its platforms and positioned as an alternative to TCP+TLS, GQUIC is feature rich: offering reliable data transmission and secure communication. It addresses TCP+TLS's (i) Head of Line Blocking (HoLB), (ii) excessive round-trip times on connection establishment, and (iii) entrenchment. Efforts by the IETF are in progress to standardize the next generation of HTTP's (HTTP/3, or H3) delivery, with their own variant of QUIC. While performance benchmarks have been conducted between GQUIC and HTTP/2-over-TCP (H2), no such analysis to our knowledge has taken place between H2 and H3. In addition, past studies rely on Page Load Time as their main, if not only, metric. The purpose of this work is to benchmark the latest draft specification of H3 and dig further into a user's Quality of Experience (QoE) using Lighthouse: an open source (and metric diverse) auditing tool. Our findings show that, for one of H3's early implementations, H3 is mostly worse but achieves a higher average throughpu

An Investigation on Software-Defined Networks’ Reactive Routing against BitTorrent

International audienceTechnologies in Software-Defined Networks (SDNs) introduce program-matic ways to reorganize the network logical topology. A possible practical usage of SDNs is Reactive Routing, where the logical topology is continuously evolving based on traffic statistics and policies. Usually, the SDNs controllers are considered transparent to the higher layers. It is expected that changes in logical topology may not affect applications. Our goal is to study the impact of logical topology changes on BitTorrent, a popular peer-to-peer protocol in practice. In this paper, we focus on BitTorrent and the experimental results show that BitTorrent may produce the opposite effect to the one expected. We have run 32 BitTorrent clients in an emulated SDN ring topology and changed the virtual topology periodically by removing one link at the time from the ring. The experiments produced lower propagation when logical topology changed periodically than when it was static for BitTorrent traffic. For comparison, we recreated the same experiments using HTTP. For HTTP, we obtained slower propagation when logical topology changed than when it was static. We discuss the results and conclude that high layer protocols need to be carefully studied, and in some cases adapted, before being deployed in SDNs