Publications

In-network Congestion Control for Multirate Multicast

Authors: George Paschos, Li Chih-Ping, Eytan Modiano, Kostas Choumas and Thanasis Korakis

Journal: IEEE/ACM Transactions on Networking (TNET), December 2015

Abstract: We present a novel control scheme that dynamically optimizes multirate multicast. By computing the differential backlog at every node, our scheme adaptively allocates transmission rates per session/user pair in order to maximize throughput. An important feature of the proposed scheme is that it does not require source cooperation or centralized calculations. This methodology leads to efficient and distributed algorithms that scale gracefully and can be embraced by low-cost wireless devices. Additionally, it is shown that maximization of sum utility is possible by the addition of a virtual queue at each destination node of the multicast groups. The virtual queue captures the desire of the individual user and helps in making the correct resource allocation to optimize total utility. Under the operation of the proposed schemes backlog sizes are deterministically bounded, which provides delay guarantees on delivered packets. To illustrate its practicality, we present a prototype implementation in the NITOS wireless testbed. The experimental results verify that the proposed schemes achieve maximum performance while maintaining low complexity.

Download paper: kohoumas_tnet_2015_multirate.pdf

CPU Provisioning Algorithms for Service Differentiation in Cloud-Based Environments

Authors: Kostas Katsalis, George Paschos, Yiannis Viniotis and Leandros Tassiulas

Journal: IEEE Transactions on Services and Network Management (TNSM), Special issue, January 2014

This work focuses on the design, analysis and evaluation of Dynamic Weighted Round Robin (DWRR) algorithms that can guarantee CPU service shares in clusters of servers. Our motivation comes from the need to provision multiple server CPUs in cloud-based data center environments. Using stochastic control theory we show that a class of DWRR policies provide the service differentiation objectives, without requiring any knowledge about the arrival and the service process statistics. The member policies provide the data center administrator with trade-off options, so that the communication and computation overhead of the policy can be adjusted. We further evaluate the proposed policies via simulations, using both synthetic and real traces obtained from a medium scale mobile computing application.

Download paper: CPU Provisioning Algorithms for Service Differentiation in Cloud-based Environments

 

Content Placement in Heterogeneous End-to-End Virtual Networks

Authors: Kostas Katsalis, Vasilis Sourlas, Thanasis Papaioannou, Thanasis Korakis and Leandros Tasssiulas

Conference: ACM/SIGAPP Symposium On Applied Computing, Salamanca, Spain, 13-17 April, 2015

Abstract: One of the distinctive features of the new virtualized ecosystem, is the multi-stakeholder participation in the way cloud services are designed, deployed and offered. In this work, we address the emerging content replication problem a Content Delivery Network (CDN) provider needs to consider, when deploying its network over multi-domain, heterogeneous environments, where virtual network operators utilize both the CDN services and the virtualized infrastructures. In our model, the benefit that the CDN provider enjoys may be different per network operator for the same request, while our model takes into account the replication cost to every domain, as well as the user mobility, besides physical storage limitations. Since the optimal placement of the objects at the caches of the various domains resembles the multiple knapsack problem, which is NP-complete, we provide two approximate solutions to the emerging content placement problem. We evaluate the proposed policies through extensive simulations and we compare them against a myopic method, where a domain is unaware of the caching strategy of the other domains that is connected to.

Download paper: Content Placement in Heterogeneous End-to-End Virtual Networks

Virtual 802.11 Wireless Networks with Guaranteed Throughput Sharing

Authors: Kostas Katsalis, Kostas Choumas, Thanasis Korakis and Leandros Tasssiulas

Conference:  IEEE Symposium on Computers and Communications (ISCC) 2015, Larnaca, Cyprus, 06 - 09 July 2015

Abstract: In this work, we present how programmable dataplane technology (software routers) offers an easy-to-apply mechanism to create virtual wireless networks and support buffering and scheduling decisions. Furthermore, we present a feedbackbased buffering mechanism that is able to provide throughput ratio guarantees per virtual network, without requiring any modifications in the 802.11 driver and without relying on statistical knowledge of the workload per virtual network or knowledge regarding the channel conditions. We implement the proposed mechanism in a software router in a 802.11 Access Point and we evaluate its performance in a wireless testbed environment. The methodology and the mechanics developed are generic and with some modifications can be applied to differentiating services for other types of guarantees like delay.

Download paper: Virtual 802.11 Wireless Networks with Guaranteed Throughout Sharing

More Articles ...

  1. A Demonstration of Evolved User Equipment for Collaborative Wireless Backhauling in Next Generation Cellular Networks
  2. Evolved User Equipment for Collaborative Wireless Backhauling in Next Generation Cellular Networks
  3. Testbed Innovations for Experimenting with Wired and Wireless Software Defined Networks
  4. Enabling Open Access to LTE network components; the NITOS testbed paradigm