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001-es BibID:BIBFORM127125
035-os BibID:(Scopus)85215868427
Első szerző:Do, Tien Van
Cím:Properties of Horizontal Pod Autoscaling Algorithms and Application for Scaling Cloud-Native Network Functions / Tien Van Do, Nam H. Do, Rotter Csaba, Lakshman T.V., Biro Csaba, Bérczes T.
Dátum:2025
ISSN:2373-7379
Megjegyzések:With the growing adoption of network function virtualization, telco core network elements and network functions will increasingly be designed and deployed as cloud-native application instances. To ensure the efficient use of virtualised resources and meet diverse requirements for quality of services a resource scaling algorithm is used to scale the the number of application instances up or down depending on variations in offered traffic from customers. Most of the observed performance metrics for a service are a function of the current customer traffic and the current number of application instances providing the service. The ubiquitous use of Kubernetes, the popular open-source framework for deployment and management of cloud-native functions, has resulted in variants of the Kubernetes Horizontal Pod Autoscaling (HPA) algorithm being widely used to change the number of application instances providing network functions as traffic demands vary. This change is done by determining whether a selected performance metric of interest is outside a range set by two input parameters (the desired metric value and the tolerance parameter). In this paper, we invesitigate the characteristics of the HPA algorithms and prove that there are only a finite number of intervals for its tolerance parametere. Further any choice of the tolerance parameter from each interval leads to similar computational decisions on the recommended number of application instances. As a consequence, the number of parameter setting choices is finite due to the rule that the desired metric value can only be an integer in specific ranges. Additionally, we investigate the use of HPA for scaling application instances that provide session-based services and establish lower and the upper bounds for performance of the HPA scaling algorithms in this scenario. Our contributions can help operators find appropriate parameter settings efficiently - administrators of Kubernetes clusters only need to select parameters from a limited and finite number of choices (instead of infinite) for scaling cloud-native applications.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:IEEE Transactions on Network and Service Management. - 22 : 2 (2025), p. 1889-1898. -
További szerzők:Do, Nam H. Rotter Csaba Lakshman, T.V. Biró Csaba Bérczes Tamás (1975-) (informatikus)
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2.

001-es BibID:BIBFORM052245
Első szerző:Do, Tien Van
Cím:A New Finite-source Queueing Model for Mobile Cellular Networks Applying Spectrum Renting / Tien Van Do, Patrick Wüchner, Tamás Bérczes, János Sztrik, Hermann de Meer
Dátum:2014
ISSN:0217-5959
Megjegyzések:This paper proposes a retrial queueing model with the finite number of sources to evaluate the performance of spectrum renting in mobile cellular networks. The model incorporates necessary ingredients such as the finite number of subscribers, their impatience and aqueue for the outbound service. To consider the specific feature of spectrum renting and the current mobile cellular technology, a variable number of servers that are switched on and off in groups is introduced. We present a novel way to take into account the renting fee, which can be used to fine-tune the operation of the spectrum renting procedure.Numerical results show that it is still profitable to initiate a spectrum renting request at high loads, even if no discount is offered by the frequency bands' owners.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Mobile cellular networks
retrial queues
finite-source
impatience
spectrum renting
discount factor
Hálózatok modellezése és analízise
Megjelenés:Asia-Pacific Journal Of Operational Research. - 31 : 02 (2014), p. 1440004_1-1440004_19. -
További szerzők:Wüchner, Patrick Bérczes Tamás (1975-) (informatikus) Sztrik János (1953-) (informatikus, matematikus) Meer, Hermann de
Pályázati támogatás:TÁMOP-4.2.2.C-11/1/KONV-2012-0001
TÁMOP
Hálózatok modellezése és hatékonyságvizsgálatai
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3.

001-es BibID:BIBFORM048051
Első szerző:Do, Tien Van
Cím:An efficient method to solve a two-server heterogeneous retrial queue with threshold policy / T. V. Do, R. Chakka, J. Sztrik, T. Bérczes, D. Efrosinin
Dátum:2013
Megjegyzések:In this paper we introduce a new method to examine a Markovian queueing systemwith two-server heterogeneous retrial queue with threshold policy and constant retrial rate.The system operates under a threshold policy:we used the faster server whenever it is idle anda customer tries to occupy it.The slower server can be activated only when the numberof waiting customers exceeds a threshold level.The model of the system can describe as a quasi-birth-and-death (QBD) process with threshold dependent block-tridiagonal infinitesimal matrix.The computation of the rate matrix R (the minimal non-negative solution to the matrix equation)can be expressed in a closed formula.The main performance measures were calculated.
ISBN:978-606-93094-8-3
Tárgyszavak:Műszaki tudományok Informatikai tudományok előadáskivonat
Controllable queueing system
retrial queue
Megjelenés:Pre-Proceedings of 9th International Conference on Applied Mathematics : 25-28 September, 2013 Baia Mare, Romania. - p. 71-73. -
További szerzők:Chakka, R. Sztrik János (1953-) (informatikus, matematikus) Bérczes Tamás (1975-) (informatikus) Efrosinin, Dmitry
Pályázati támogatás:TÁMOP-4.2.2.C-11/1/KONV-2012-0001
TÁMOP
Hálózatok modellezése és analízise
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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4.

001-es BibID:BIBFORM136558
Első szerző:Gao, Shan
Cím:Reliability evaluation and optimization for a redundant repairable cluster computing system / Gao, Shan; Do, Tien Van; Hajdú, András; Bérczes, Tamás; Wang, Jinting
Dátum:2026
ISSN:0951-8320
Megjegyzések:This paper proposes a model for evaluating the reliability of cluster computing systems composed of failure-prone nodes, a primary repair unit, and a backup repair facility. The backup facility remains unactivated when no nodes have failed. It is activated immediately if either: (1) the repair time for a failed node at the primary facility exceeds a predefined threshold, or (2) the number of failed nodes surpasses a separate threshold. Once activated, the backup facility operates continuously until all failed nodes are restored. We first derive transient-state reliability measures using a Markov process framework. Building on solutions to second-order linear homogeneous variable-coefficient difference equations, we obtain closed-form expressions for the system`s steady-state distribution and derive associated steady-state reliability and performance metrics. Subsequently, leveraging phase-type distribution properties, we formulate expressions for the system`s reliability function and mean time to first failure (MTTFF). Finally, sensitivity analyses demonstrate the necessity and effectiveness of backup repair facilities. We further address a cost-effectiveness optimization problem subject to steady-state availability constraint. The proposed modeling approach applies to diverse repairable redundant systems requiring fault tolerance and backup mechanisms-such as modern data centers, edge computing deployments, and high-availability network infrastructures.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Cluster computing system
Reliability
Backup repair facility
(T,M) policy
Cost-benefit optimization
Megjelenés:Reliability Engineering & System Safety. - 272 : 3 (2026), p. 1-18
További szerzők:Do, Tien Van Hajdu András (1973-) (matematikus, informatikus) Bérczes Tamás (1975-) (informatikus) Wang, Jinting (1965-) (matematikus informatikus)
Pályázati támogatás:K-138208
OTKA
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DOI
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5.

001-es BibID:BIBFORM125218
035-os BibID:(Scopus)85205756822
Első szerző:Vajda Dániel László
Cím:Machine learning-based real-time anomaly detection using data pre-processing in the telemetry of server farms / Dániel László Vajda, Tien Van Do, Tamás Bérczes, Károly Farkas
Dátum:2024
ISSN:2045-2322
Megjegyzések:Fast and accurate anomaly detection is critical in telemetry systems because it helps operators take appropriate actions in response to abnormal behaviours. However, recent techniques are accurate but not fast enough to deal with real-time data. There is a need to reduce the anomaly detection time, which motivates us to propose two new algorithms called AnDePeD (Anomaly Detector on Periodic Data) and AnDePed Pro. The novelty of the proposed algorithms lies in exploiting the periodic nature of data in anomaly detection. Our proposed algorithms apply a variational mode decomposition technique to find and extract periodic components from the original data before using Long ShortTerm Memory neural networks to detect anomalies in the remainder time series. Furthermore, our methods include advanced techniques to eliminate prediction errors and automatically tune operational parameters. Extensive numerical results show that the proposed algorithms achieve comparable performance in terms of Precision, Recall, F-score, and MCC metrics while outperforming most of the state-of-the-art anomaly detection approaches in terms of initialisation delay and detection delay, which is favourable for practical applications.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Server farm telemetry
Real-time anomaly detection
Periodic data
Pre-processing
AnDePeD
AnDePeD Pro
VMD
Mode removal
Megjelenés:Scientific Reports. - 14 : 1 (2024), p. 1-22. -
További szerzők:Do, Tien Van Bérczes Tamás (1975-) (informatikus) Farkas Károly (1975-) (informatikus)
Pályázati támogatás:K-138208
OTKA
Internet cím:Szerző által megadott URL
DOI
Intézményi repozitóriumban (DEA) tárolt változat
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