TY - CONF AB - Video streaming is in high demand by mobile users. In cellular networks, however, the unreliable wireless channel leads to two major problems. Poor channel states degrade video quality and interrupt the playback when a user cannot sufficiently fill its local playout buffer: buffer underruns occur. In contrast, good channel conditions cause common greedy buffering schemes to buffer too much data. Such over-buffering wastes expensive wireless channel capacity. Assuming that we can anticipate future data rates, we plan the quality and download time of video segments ahead. This anticipatory download scheduling avoids buffer underruns by downloading a large number of segments before a drop in available data rate occurs, without wasting wireless capacity by excessive buffering.We developed a practical anticipatory scheduling algorithm for segmented video streaming protocols (e.g., HLS or MPEG DASH). Simulation results and testbed measurements show that our solution essentially eliminates playback interruptions without significantly decreasing video quality. AU - Dräxler, Martin AU - Blobel, Johannes AU - Dreimann, Philipp AU - Valentin, Stefan AU - Karl, Holger ID - 252 T2 - Proceedings of the 2nd International Conference on Networked Systems (NetSys) TI - SmarterPhones: Anticipatory Download Scheduling for Wireless Video Streaming ER - TY - CONF AB - The size of modern data centers is constantly increasing. As it is not economic to interconnect all machines in the data center using a full-bisection-bandwidth network, techniques have to be developed to increase the efficiency of data-center networks. The Software-Defined Network paradigm opened the door for centralized traffic engineering (TE) in such environments. Up to now, there were already a number of TE proposals for SDN-controlled data centers that all work very well. However, these techniques either use a high amount of flow table entries or a high flow installation rate that overwhelms available switching hardware, or they require custom or very expensive end-of-line equipment to be usable in practice. We present HybridTE, a TE technique that uses (uncertain) information about large flows. Using this extra information, our technique has very low hardware requirements while maintaining better performance than existing TE techniques. This enables us to build very low-cost, high performance data-center networks. AU - Wette, Philip AU - Karl, Holger ID - 287 T2 - Proceedings of the 4th European Workshop on Software Defined Networks (EWSDN 2015) TI - HybridTE: Traffic Engineering for Very Low-Cost Software-Defined Data-Center Networks ER - TY - CONF AB - Multi-rooted trees are becoming the norm for modern data-center networks. In these networks, scalable flow routing is challenging owing to vast number of flows. Current approaches either employ a central controller that can have scalability issues or a scalable decentralized algorithm only considering local information. In this paper we present a new decentralized approach to least-congested path routing in software-defined data center networks that has neither of these issues: By duplicating the initial (or SYN) packet of a flow and estimating the data rate of multiple flows in parallel, we exploit TCP’s habit to fill buffers to find the least congested path. We show that our algorithm significantly improves flow completion time without the need for a central controller or specialized hardware. AU - Schwabe, Arne AU - Karl, Holger ID - 247 T2 - Proceedings of the 4th European Workshop on Software Defined Networks (EWSDN 2015) TI - SynRace: Decentralized Load-Adaptive Multi-path Routing without Collecting Statistics ER - TY - THES AU - Wette, Philip ID - 264 TI - Optimizing Software-Defined Networks using Application-Layer Knowledge ER - TY - CONF AU - A. Aranda-Gutierrez, Pedro AU - Karl, Holger AU - Rojas, Elisa AU - Leckey, Alec ID - 739 T2 - 2015 European Conference on Networks and Communications, EuCNC 2015, Paris, France, June 29 - July 2, 2015 TI - On Network Application representation and controller independence in {SDN ER - TY - CONF AU - Blanckenstein, Johannes AU - Nardin, Cristina AU - Klaue, Jirka AU - Karl, Holger ID - 742 T2 - {IEEE} International Conference on Communication, {ICC} 2015, London, United Kingdom, June 8-12, 2015, Workshop Proceedings TI - Error characterization of multi-access point WSNs in an aircraft cabin ER - TY - CONF AU - Schwabe, Arne AU - Karl, Holger ID - 743 T2 - 2015 IEEE International Conference on Communications, ICC 2015, London, United Kingdom, June 8-12, 2015 TI - Topology model to generate realistic latency for simulations ER - TY - CONF AU - Dräxler, Martin AU - Blobel, Johannes AU - Karl, Holger ID - 745 T2 - 8th IFIP Wireless and Mobile Networking Conference, WMNC 2015, Munich, Germany, October 5-7, 2015 TI - Anticipatory Download Scheduling in Wireless Video Streaming with Uncertain Data Rate Prediction ER - TY - CONF AU - Wette, Philip AU - Schwabe, Arne AU - Splietker, Malte AU - Karl, Holger ID - 746 T2 - Proceedings of the 1st {IEEE} Conference on Network Softwarization, NetSoft 2015, London, United Kingdom, April 13-17, 2015 TI - Extending Hadoop's Yarn Scheduler Load Simulator with a highly realistic network & traffic model ER - TY - CONF AU - Auroux, Sébastien AU - Karl, Holger ID - 747 T2 - 26th IEEE Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, PIMRC 2015, Hong Kong, China, August 30 - September 2, 2015 TI - Flexible reassignment of flow processing-aware controllers in future wireless networks ER - TY - CONF AU - Auroux, Sébastien AU - Karl, Holger ID - 748 T2 - 2015 IEEE Wireless Communications and Networking Conference, WCNC 2015, New Orleans, LA, USA, March 9-12, 2015 TI - Efficient flow processing-aware controller placement in future wireless networks ER - TY - GEN AU - Dräxler, Sevil AU - Karl, Holger ID - 749 T2 - CoRR TI - Specification of Complex Structures in Distributed Service Function Chaining Using a YANG Data Model ER - TY - GEN AU - Dräxler, Martin AU - Karl, Holger ID - 750 T2 - CoRR TI - Dynamic Backhaul Network Configuration in SDN-based Cloud RANs ER - TY - CONF AB - The increasing amount of mobile traffic leads to a significantly higher energy consumption of mobile networks that is mainly caused by the high number of required base stations. One recent solution for this is based on a two-layered network that uses long-range macro cells to provide a full coverage signaling overlay and short-range small cells for fast data transmissions. These small cells can be switched off when they are not needed and allow network-wide energy optimizations. This paper presents an architecture that extends existing mobile networks to integrate a small cell layer that supports on-demand cell activation. We discuss how additional small cells can be interconnected with existing core components and how they can be controlled by a resource management component. Finally, a Wi-Fi based proof of concept testbed implementation is presented that demonstrates the feasibility of the approach. AU - Peuster, Manuel AU - Karl, Holger ID - 986 T2 - Proceedings of the 5th Workshop on All Things Cellular: Operations, Applications and Challenges TI - An Architecture for Energy-aware On-demand Mobile Network Management ER - TY - CONF AU - Auroux, Sébastien AU - Draxler, Martin AU - Morelli, Arianna AU - Mancuso, Vincenzo ID - 1636 SN - 9781467373593 T2 - 2015 European Conference on Networks and Communications (EuCNC) TI - Dynamic network reconfiguration in wireless DenseNets with the CROWD SDN architecture ER - TY - CONF AB - Network emulations are widely used for testing novel network protocols and routing algorithms in realistic scenarios. Up to now, there is no emulation tool that is able to emulate large software-defined data center networks that consist of several thousand nodes. Mininet is the most common tool to emulate Software-Defined Networks of several hundred nodes. We extend Mininet to span an emulated network over several physical machines, making it possible to emulate networks of several thousand nodes on just a handful of physical machines. This enables us to emulate, e.g., large data center networks. To test this approach, we additionally introduce a traffic generator for data center traffic. Since there are no data center traffic traces publicly available we use the results of two recent traffic studies to create synthetic traffic. We show the design and discuss some challenges we had in building our traffic generator. As a showcase for our work we emulated a data center consisting of 3200 hosts on a cluster of only 12 physical machines. We show the resulting workloads and the trade-offs involved. AU - Wette, Philip AU - Dräxler, Martin AU - Schwabe, Arne AU - Wallaschek, Felix AU - Zahraee, Mohammad Hassan AU - Karl, Holger ID - 329 T2 - Proceedings of the 2014 IFIP Networking Conference (Networking 2014) TI - MaxiNet: Distributed Emulation of Software-Defined Networks ER - TY - CONF AB - Preemptive Routing and Wavelength Assignment (RWA) algorithms preempt established lightpaths in case notenough resources are available to set up a new lightpath in aWavelength Division Multiplexing (WDM) network. The selectionof lightpaths to be preempted relies on internal decisions of theRWA algorithm. Thus, if dedicated properties of the networktopology are required by the applications running on the network,these requirements have to be known to the RWA algorithm.We present a family of preemptive RWA algorithms for WDMnetworks. These algorithms have two distinguishing features: a)they can handle dynamic traffic by on-the-fly reconfiguration,and b) users can give feedback for reconfiguration decisions andthus influence the preemption decision of the RWA algorithm,leading to networks which adapt directly to application needs.This is different from traffic engineering where the network is(slowly) adapted to observed traffic patterns.Our algorithms handle various WDM network configurationsincluding networks consisting of heterogeneous WDM hardware.To this end, we are using the layered graph approach togetherwith a newly developed graph model that is used to determineconflicting lightpaths. AU - Wette, Philip AU - Karl, Holger ID - 339 T2 - Proceedings of the IEEE International Conference on Communications 2014 TI - Using Application Layer Knowledge in Routing and Wavelength Assignment Algorithms ER - TY - THES AU - Künsemöller, Jörn ID - 343 TI - Tragedy of the Common Cloud - Game Theory on the Infrastructure-as-a-Service Market ER - TY - CONF AB - In distributed cloud computing, application deployment across multiple sites can improve quality of service. Recent research developed algorithms to find optimal locations for virtual machines. However, those algorithms assume to have either single-tier applications or a fixed number of virtual machines – a strong simplification of reality. This paper investigates the placement and scaling of complex application architectures. An application is dynamically scaled to fit both the current demand situation and the currently available infrastructure resources. We compare two approaches: The first one is based on virtual network embedding. The second approach is a novel method called Template Embedding. It is based on a hierarchical 1-allocation hub flow problem and combines applica- tion scaling and embedding in one step. Extensive experiments on 43200 network configurations showed that Template Embedding outperforms virtual network embedding in all cases in three metrics: success rate, solution quality, and runtime. This positive result shows that template embedding is a promising approach for distributed cloud resource allocation. AU - Keller, Matthias AU - Robbert, Christoph AU - Karl, Holger ID - 354 T2 - Proceedings of 7th International Conference on Utility and Cloud Computing (UCC) TI - Template Embedding: Using Application Architecture to Allocate Resources in Distributed Clouds ER - TY - CONF AB - 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. AU - Dräxler, Sevil AU - Keller, Matthias AU - Karl, Holger ID - 360 T2 - Proceedings of the 3rd International Conference on Cloud Networking (CloudNet) TI - Specifying and Placing Chains of Virtual Network Functions ER -