Analyzing response time of batch signing

Abstract Digital signatures are mainly used to make the receiver believe that a document is actually sent by the claimed sender. However, since generating digital signatures requires intensive computations, researchers proposed batch signing systems to sign multiple documents at once while having almost the same cost of signing one document. In this paper, we analyze how the batch formation strategies and batch sizes impact the response time. Using simulations, we verify our analytical results obtained under the assumption of non-bursty arrivals. We also consider bursty arrivals in our simulations. In general, we observe that using appropriate batch sizes and strategies minimizes the response time in all cases. The improvements are specifically significant when the arrival rate is bursty and dynamic bach sizes are used

OPC UA suorituskyvyn arviointi

OPC Unified Architecture is an industrial communication specification, employing a client-server communication model. In this thesis, performance testing of OPC UA applications is explored. First, performance testing of software applications is discussed on a general level. After this, details of OPC UA and previous studies of OPC UA performance are examined. Based on this information, example test cases are designed. The testing procedure and results of the tests are presented in detail. As an important part of the work, the design and implementation of a generic test client for read and subscription testing is presented. The results provide information about overhead of OPC UA security modes in two different hardware platforms and comparison of two server applications in terms of read and subscription functionality. Substantial differences can be observed in terms of maximum number of requests as well as in the resulting resource usage. When overloaded, the servers again exhibit differences in their behavior. The test results should be thought of as examples of features, limits and differences that can be observed by performance testing OPC UA applications. The results of this thesis are used in the future development of the Prosys OPC UA Java SDK.OPC Unified Architecture on erityisesti teollisiin ympäristöihin suunniteltu tiedonsiirtomäärittely, joka käyttää asiakas-palvelin kommunikointimallia. Tässä työssä tutkitaan OPC UA -sovellusten suorituskykytestausta. Ensin muodostetaan yleisellä tasolla käsitys tavoista mitata ohjelmistojen suorituskykyä. Tämän jälkeen OPC UA -määrittelyn yksityiskohtia käydään läpi tähän työhön liittyvin osin. Aiemmin aihepiiristä julkaistujen tutkimusten avulla muodostetaan kuva siitä, mitä ja miten oikeastaan kannattaa tutkia. Suoritettavat testit dokumentoidaan mahdollisimman hyvin ja testien tulokset raportoidaan yksityiskohtaisesti. Tärkeänä osana työtä esitellään yleiskäyttöisen testisovelluksen suunnittelu ja toteutus. Tutkimuksen perusteella esitetään tietoa OPC UA -viestien tietoturvalliseen käsittelyyn kuluvasta resurssien kulutuksesta kahdella eri laitteistolla ja vertaillaan kahden OPC UA -palvelintoteutuksen ominaisuuksia. Toteutuksissa voidaan havaita selkeitä eroja käsiteltyjen pyyntöjen maksimimäärässä sekä palvelinohjelmistojen resurssienkäytössä. Kun palvelimiin tehdään enemmän pyyntöjä kuin ne ehtivät käsitellä, on tuloksena taas selkeitä eroja eri implementaatioiden välillä. Esiteltävät testitulokset pätevät tässä tietyssä konfiguraatiossa ja ne tulee käsittää esimerkkeinä siitä minkälaisia ominaisuuksia, rajoituksia ja eroja OPC UA -sovelluksissa on havaittavissa. Työn tuloksia tullaan käyttämään Prosys OPC UA Java SDK:n jatkokehityksessä

Inside Dropbox: Understanding Personal Cloud Storage Services

Personal cloud storage services are gaining popularity. With a rush of providers to enter the market and an increasing of- fer of cheap storage space, it is to be expected that cloud storage will soon generate a high amount of Internet traffic. Very little is known about the architecture and the perfor- mance of such systems, and the workload they have to face. This understanding is essential for designing efficient cloud storage systems and predicting their impact on the network. This paper presents a characterization of Dropbox, the leading solution in personal cloud storage in our datasets. By means of passive measurements, we analyze data from four vantage points in Europe, collected during 42 consecu- tive days. Our contributions are threefold: Firstly, we are the first to study Dropbox, which we show to be the most widely-used cloud storage system, already accounting for a volume equivalent to around one third of the YouTube traffic at campus networks on some days. Secondly, we characterize the workload typical users in different environments gener- ate to the system, highlighting how this reflects on network traffic. Lastly, our results show possible performance bot- tlenecks caused by both the current system architecture and the storage protocol. This is exacerbated for users connected far from control and storage data-center

Many Task Learning with Task Routing

Typical multi-task learning (MTL) methods rely on architectural adjustments and a large trainable parameter set to jointly optimize over several tasks. However, when the number of tasks increases so do the complexity of the architectural adjustments and resource requirements. In this paper, we introduce a method which applies a conditional feature-wise transformation over the convolutional activations that enables a model to successfully perform a large number of tasks. To distinguish from regular MTL, we introduce Many Task Learning (MaTL) as a special case of MTL where more than 20 tasks are performed by a single model. Our method dubbed Task Routing (TR) is encapsulated in a layer we call the Task Routing Layer (TRL), which applied in an MaTL scenario successfully fits hundreds of classification tasks in one model. We evaluate our method on 5 datasets against strong baselines and state-of-the-art approaches.Comment: 8 Pages, 5 Figures, 2 Table

Patterns for service-oriented information exchange requirements

Service-Oriented Computing (SOC) is an emerging computing paradigm that supports loosely-coupled inter-enterprise interactions. SOC interactions are predominantly specified in a procedural manner that defines message sequences intermixing implementation with business requirements. In this paper we present a set of patterns concerning requirements of information exchange between participants engaging in service-oriented interactions. The patterns aim at explicating and elaborating the business requirements driving the interaction and separating them from implementation concerns