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Sevil Dräxler, M.Sc.

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Publications
 Sevil Dräxler, M.Sc.

Computer Networks

Member - Research Assistant

Phone:
+49 5251 60-1755
Office:
O3.161 (Map)
Office hours:

Mo. 13:00-14:00

Web:
Visitor:
Pohlweg 51
33098 Paderborn
Postal Address:
Warburger Str. 100
33098 Paderborn

International Graduate School Dynamic Intelligent Systems

Research Student

Phone:
+49 5251 60-1755
Office:
O3.161 (Map)
Visitor:
Pohlweg 51
33098 Paderborn
Postal Address:
Warburger Str. 100
33098 Paderborn

Google Scholar

Sevil Dräxler (née Mehraghdam)

Projects

I have been involved in the following projects:

  • 5G-PICTURE: 5G Programmable Infrastructure Converging Disaggregated Network and Compute Resources (Since June 2017) 

  • SFB 901 Subproject C4: On-The-Fly Compute Centers II - Execution of Composed Services in Configurable Compute Centers (Since April 2014)
  • SONATA NFV: Agile Service Development and Orchestration in 5G Virtualized Networks (July 2015-December 2017)
Student Theses and Projects

I have been advising the following bachelor's and master's theses:

  • Bachelor's thesis: "Prediction of Resource Requirements and Performance of Virtualised Network Functions in a Video Streaming Context", 2017.
  • Master's thesis: "Specifying, Scaling, Placing, and Reusing Bidirectional Forwarding Graphs of Virtual Network Functions", 2017.
  • Master's thesis: "Optimizing Placement and Scaling of Chained Virtualized Network Functions", 2016.

I have also advised the following project groups:

  • SCrAMbLE: management of ServiCes Across MultipLE clouds (WS18-SS18/19)

  • SanDMAN: Service Development and Management for softwAre-defined Networks (SS16-WS16/17)

  • DECaF: DistributEd Cloud Functions (SS15-WS15/16)

You can find a list of currently open topics in our research group here​. If you are interested in writing a thesis in the area of flexibe and efficient management and orchestration of services consisting of virtulized network functions, especially, optimization of placement and scaling of composed services, just drop me an email.


Open list in Research Information System

Scaling and Placing Bidirectional Services with Stateful Virtual and Physical Network Functions

S. Dräxler, S.B. Schneider, H. Karl, in: 4th IEEE International Conference on Network Softwarization (NetSoft 2018), 2018

Network function virtualization requires scaling and placement, deciding the number and the location of function instances. Current approaches are limited in flexibility and practical applicability. Specifically, we study dynamic, single-step, joint scaling and placement of network services with bidirectional flows traversing Physical or Virtual Network Functions (VNFs) and returning to their sources. We develop models to support stateful components and legacy network functions with fixed locations in these network services as well as the possibility of reusing VNFs across network services. We formalize the problem of jointly scaling and placing such network services as a mixed- integer linear program (MILP). We show that this problem is NP-complete and also present a heuristic algorithm to find good solutions in short time. In an extensive evaluation with realistic scenarios, we investigate the capabilities of the two approaches.


5G OS: Control and Orchestration of Services on Multi-Domain Heterogeneous 5G Infrastructures

S. Dräxler, H. Karl, H. Razzaghi Kouchaksaraei, A. Machwe, C. Dent-Young, K. Katsalis, K. Samdanis, in: 27th European Conference on Networks and Communications (EUCNC 2018), 2018


JASPER: Joint Optimization of Scaling, Placement, and Routing of Virtual Network Services

S. Dräxler, H. Karl, Z.A. Mann, IEEE Transactions on Network and Service Management (2018)

To adapt to continuously changing workloads in networks, components of the running network services may need to be replicated (scaling the network service) and allocated to physical resources (placement) dynamically, also necessitating dynamic re-routing of flows between service components. In this paper, we propose JASPER, a fully automated approach to jointly optimizing scaling, placement, and routing for complex network services, consisting of multiple (virtualized) components. JASPER handles multiple network services that share the same substrate network; services can be dynamically added or removed and dynamic workload changes are handled. Our approach lets service designers specify their services on a high level of abstraction using service templates. JASPER automatically makes scaling, placement and routing decisions, enabling quick reaction to changes. We formalize the problem, analyze its complexity, and develop two algorithms to solve it. Extensive empirical results show the applicability and effectiveness of the proposed approach.


Towards Predicting Resource Demands and Performance of Distributed Cloud Services

S. Dräxler, M. Peuster, M. Illian, H. Karl, 2018

Understanding the behavior of distributed cloud service components in different load situations is important for efficient and automatic management and orchestration of these services. For this purpose and for practical research in distributed cloud computing in general, there is need for benchmarks and experimental data. In this paper, we describe our experiments for characterizing the relationship between resource demands of application components and the expected performance of applica- tions. We present initial results for predicting the interdependence between resource demands and performance characteristics using support vector regression and polynomial regression models. The data gathered from our experiments is publicly available.


Programmable and Flexible Management and Orchestration of Virtualized Network Functions

H. Razzaghi Kouchaksaraei, S. Dräxler, M. Peuster, H. Karl, IEEE, 2018

Supporting the vast variety of network services’ management and orchestration requirements is one of the main challenges that Network Function Virtualization (NFV) is dealing with. While general management requirements such as Virtual Network Function (VNF) resource requirements can be specified by the service developers using service descriptors, specific management operations like VNF-specific configuration cannot be performed by these descriptors. On the other hand, it is inefficient and also very challenging for Management and Orchestration (MANO) frameworks to provide all specific-management operations for every individual network service and their constituent VNFs. To mitigate this issue, we propose the use of service-specific programs called Specific Managers (SMs) that can customize management and orchestration of network services and also extend the capability of MANO frameworks to support per-service management and orchestration. The results of our evaluation show that the higher flexibility and programmability enabled by SMs improve the performance of the service performance and also utilises the service provider resources more efficiently.


Generating Resource and Performance Models for Service Function Chains: The Video Streaming Case

S. Dräxler, M. Peuster, M. Illian, H. Karl, in: 4th IEEE International Conference on Network Softwarization (NetSoft 2018), IEEE, 2018, pp. 318--322

Understanding the behavior of the components of service function chains (SFCs) in different load situations is important for efficient and automatic management and orches- tration of services. For this purpose and for practical research in network function virtualization in general, there is a great need for benchmarks and experimental data. In this paper, we describe our experiments for characterizing the relationship between resource demands of virtual network functions (VNFs) and the expected performance of the SFC, considering the individual performance of the VNFs as well as the interdependencies among VNFs within the SFC. We have designed our experiments focusing on video streaming, an important application in this context. We present examples of models for predicting the interdependence between resource demands and performance characteristics of SFCs using support vector regression and polynomial regression models. We also show practical evidence from our experiments that VNFs need to be benchmarked in their final chain setup, rather than individually, to capture important interdependencies that affect their performance. The data gathered from our experiments is publicly available.


A flexible multi-pop infrastructure emulator for carrier-grade MANO systems

M. Peuster, S. Dräxler, H. Razzaghi Kouchaksaraei, S.v. Rossem, W. Tavernier, H. Karl, in: 2017 IEEE Conference on Network Softwarization (NetSoft), IEEE, 2017

Developing a virtualized network service does not only involve the implementation and configuration of the network functions it is composed of but also its integration and test with management solutions that will control the service in its production environment. These integration tasks require testbeds that offer the needed network function virtualization infrastructure (NFVI), like OpenStack, introducing a lot of management and maintenance overheads. Such testbed setups become even more complicated when the multi point-of-presence (PoP) case, with multiple infrastructure installations, is considered. In this demo, we showcase an emulation platform that executes containerized network services in user-defined multi-PoP topologies. The platform does not only allow network service developers to locally test their services but also to connect realworld management and orchestration solutions to the emulated PoPs. During our interactive demonstration we focus on the integration between the emulated infrastructure and state-of-theart orchestration solutions like SONATA or OSM.


Joint Optimization of Scaling and Placement of Virtual Network Services

S. Dräxler, H. Karl, Z.A. Mann, in: Proceedings of the 17th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing (CCGrid 2017), 2017

Management of complex network services requires flexible and efficient service provisioning as well as optimized handling of continuous changes in the workload of the service.To adapt to changes in the demand, service components need to be replicated (scaling) and allocated to physical resources (placement) dynamically. In this paper, we propose a fullyautomated approach to the joint optimization problem of scaling and placement, enabling quick reaction to changes. We formalize the problem, analyze its complexity, and develop two algorithms to solve it. Extensive empirical results show the applicability andeffectiveness of the proposed approach.


A flexible multi-pop infrastructure emulator for carrier-grade MANO systems

M. Peuster, S. Dräxler, H. Razzaghi Kouchaksaraei, S. van Rossem, W. Tavernier, H. Karl, in: IEEE Conference on Network Softwarization, NetSoft 2017, Bologna, Italy, July 3-7, 2017, 2017, pp. 1--3

Developing a virtualized network service does not only involve the implementation and configuration of the network functions it is composed of but also its integration and test with management solutions that will control the service in its production environment. These integration tasks require testbeds that offer the needed network function virtualization infrastructure~(NFVI), like OpenStack, introducing a lot of management and maintenance overheads. Such testbed setups become even more complicated when the multi point-of-presence~(PoP) case, with multiple infrastructure installations, is considered. In this demo, we showcase an emulation platform that executes containerized network services in user-defined multi-PoP topologies. The platform does not only allow network service developers to locally test their services but also to connect real-world management and orchestration solutions to the emulated PoPs. During our interactive demonstration we focus on the integration between the emulated infrastructure and state-of-the-art orchestration solutions like SONATA or OSM.


Specification, Composition, and Placement of Network Services with Flexible Structures

S. Dräxler, H. Karl, International Journal of Network Management (2017), pp. 1--16

Network function virtualization and software-defined networking allow services consisting of virtual network functions to be designed and implemented with great flexibility by facilitating automatic deployments, migrations, and reconfigurations for services and their components. For extended flexibility, we go beyond seeing services as a fixed chain of functions. We define the service structure in a flexible way that enables changing the order of functions in case the functionality of the service is not influenced by this, and propose a YANG data model for expressing this flexibility. Flexible structures allow the network orchestration system to choose the optimal composition of service components that for example gives the best results for placement of services in the network. When number of flexible services and number of components in each service increase, combinatorial explosion limits the practical use of this flexibility. In this paper, we describe a selection heuristic that gives a Pareto set of the possible compositions of a service as well as possible combinations of different services, with respect to different optimization objectives. Moreover, we present a heuristic algorithm for placement of a combination of services, which aims at placing service components along shortest paths that have enough capacity for accommodating the services. By applying these solutions, we show that allowing flexibility in the service structure is feasible.


SONATA: Service programming and orchestration for virtualized software networks

S. Dräxler, H. Karl, M. Peuster, H. Razzaghi Kouchaksaraei, M. Bredel, J. Lessmann, T. Soenen, W. Tavernier, S. Mendel-Brin, G. Xilouris, in: 2017 IEEE International Conference on Communications Workshops (ICC Workshops), IEEE, 2017

In conventional large-scale networks, creation and management of network services are costly and complex tasks that often consume a lot of resources, including time and manpower. Network softwarization and network function virtualization have been introduced to tackle these problems, aiming at decreasing costs and complexity of implementing new services, maintaining the implemented services, and managing available resources in service provisioning platforms and underlying infrastructures. To experience the full potential of these approaches, innovative development support tools and service provisioning environments are needed. To answer these needs, we introduce the architecture of the open-source SONATA system, a service programming, orchestration, and management framework. We present a development toolchain for virtualized network services, fully integrated with a service platform and orchestration system. We introduce the modular and flexible architecture of our system and discuss its main components and features, such as function- and service-specific managers that allow fine-grained service management, slicing support to facilitate multi-tenancy, recursiveness for improved scalability, and full-featured DevOps support.


SONATA: Service Programming and Orchestration for Virtualised Software Networks

S. Dräxler, H. Karl, H. Razzaghi Kouchaksaraei, M. Peuster, M. Bredel, J. Lessmann, T. Soenen, W. Tavernier, S. Mendel-Brin, G. Xilouris, in: Communications Workshops (ICC Workshops), 2017 IEEE International Conference on, 2017

DOI


DevOps for network function virtualisation: an architectural approach

H. Karl, S. Dräxler, M. Peuster, A. Galis, M. Bredel, A. Ramos, J. Martrat, M.S. Siddiqui, S. van Rossem, W. Tavernier, G. Xilouris, Transactions on Emerging Telecommunications Technologies (2016), pp. 1206-1215

The Service Programming and Orchestration for Virtualised Software Networks (SONATA) project targets both the flexible programmability of software networks and the optimisation of their deployments by means of integrating Development and Operations in order to accelerate industry adoption of software networks and reduce time-to-market for networked services. SONATA supports network function chaining and orchestration, making service platforms modular and easier to customise to the needs of different service providers, and introduces a specialised Development and Operations model for supporting developers.


Placement of Services with Flexible Structures Specified by a YANG Data Model

S. Dräxler, H. Karl, in: Proceedings of the 2nd International IEEE Conference on Network Softwarization (NetSoft), 2016, pp. 184--192

Network function virtualization and software-defined networking allow services consisting of virtual network functions to be designed and implemented with great flexibility by facilitating automatic deployments, migrations, and reconfigurations for services and their components. For extended flexibility, we go beyond seeing services as a fixed chain of functions. We present a YANG model for describing the service structure in deployment requests in a flexible way that enables changing the order of functions in case the order of traversing them does not affect the functionality of the service. Upon receiving such requests, the network orchestration system can choose the optimal composition of service components that gives the best results for placement of services in the network. This introduces new complexities to the placement problem by greatly increasing the number of possible ways a service can be composed. In this paper, we describe a heuristic solution that selects a Pareto set of the possible compositions of a service as well as possible combinations of different services, with respect to different resource requirements of the services. Our evaluations show that the selected combinations consist of representative samples of possible structures and requirements and therefore, can result in optimal or close-to-optimal placement results.



Specifying and Placing Chains of Virtual Network Functions

S. Dräxler, M. Keller, H. Karl, in: Proceedings of the 3rd International Conference on Cloud Networking (CloudNet), 2014, pp. 7-13

Network appliances perform different functions on network flows and constitute an important part of an operator’s network. Normally, a set of chained network functions process network flows. Following the trend of virtualization of networks, virtualization of the network functions has also become a topic of interest. We define a model for formalizing the chaining of network functions using a context-free language. We process deployment requests and construct virtual network function graphs that can be mapped to the network. We describe the mapping as a Mixed Integer Quadratically Constrained Program (MIQCP) for finding the placement of the network functions and chaining them together considering the limited network resources and requirements of the functions. We have performed a Pareto set analysis to investigate the possible trade-offs between different optimization objectives.


Adaptive Placement of Programmable Virtual Network Function Chains

S. Dräxler, Universität Paderborn, 2014


Open list in Research Information System

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