Selected Publications

The full list of publications can be found in the bibliographic list of staff publications of AGH-UST. The BibTeX file with publications listed below is available for download.

P. Wydrych and P. Chołda, “Locality- and quality-awareness for P2PTV systems based on scalable video coding (SVC),” in Proc. IEEE Int Communications (ICC) Conf, London, UK, Jun. 2015. ©IEEE.

In this paper, an innovative and adaptive BitTorrent-based peer-to-peer television (P2PTV) system is proposed and investigated. It is shown how end-users of such systems and Internet Service Providers (ISPs) may benefit from simultaneous usage of both (a) the recently standardized ALTO Protocol, and (b) Scalable Video Coding (SVC). The system description is followed by a thorough evaluation of the results gathered during the simulation experiments.

P. Wydrych, K. Rusek, and P. Chołda, “Efficient modelling of traffic and quality of scalable video coding (SVC) encoded streams,” IEEE Communications Letters, vol. 17, no. 12, pp. 2372–2375, Dec. 2013. ©IEEE, available on IEEE Xplore.

In this letter, a new model for generating SVC-like traffic and estimating its quality is introduced. Comprising two independent components — i.e., the traffic generator and the quality estimator — the model can significantly speed up the development of SVC applications in various use-cases by relying on approximated properties of streams instead of real traces. The model is verified based on a set of video streams and the performance of its components is assessed.

P. Wydrych and P. Chołda, “Will P2P users cooperate with ISPs? A word-of-mouth communication approach,” (presentation) in Proc. IEEE Int Communications (ICC) Conf, Ottawa, Canada, Jun. 2012. ©IEEE, available on IEEE Xplore.

Researchers who address the problem of application-level traffic optimization often consider only the simplest comparison scenario: (a) the case before the option to cooperate and optimize the service is enabled, and (b) the case in which all clients try to optimize the traffic. In this paper, the situations that a user may not wish to cooperate or that a user does not perceive the optimization possibility to be valuable enough to cooperate are taken into account. An analytical model for estimating the popularity of the cooperate-to-optimize option is derived. A method for calculating the time-dependent value of the predicted popularity is presented. The model is verified by simulation experiments.

Z. Duliński, P. Wydrych, and R. Stankiewicz, “Inter-ALTO communication problem statement,” Internet Engineering Task Force, Internet-Draft draft-dulinski-alto-inter-problem-statement-01, Jul. 2011, work in progress.

This draft considers an approach to the optimization of the traffic generated by the overlay (peer-to-peer) applications, where some information on inter-AS (Autonomous System) paths is obtained with the usage of dedicated communication scheme known as inter-ALTO communication.

The large amount of network traffic generated by overlay applications requires effective management. This traffic traverses inter-AS links and thus generates substantial costs for the operators and poses problems with overload on the external and internal links. The traffic is not time-stable as the peers connect and disconnect very often. Additionally, when the overlay traffic is observed on inter-AS links, it can be seen that sources and destinations change in a very short period of time. The ALTO (Application-Layer Traffic Optimization) service provides the information that enables more efficient management of the overlay traffic. Such applications can use the information to perform better-than-random peer selection. The ALTO servers are responsible for a pre-selection procedure; the final selection is done by overlay clients and then the ALTO protocol conveys network information to applications. To be credible, this information should be as close to real network situation as possible. However, some types of data are not hold by an operator, but they should be gained on the basis of the additional information exchange with other AS operators. This document presents rationale for the need of introduction of the inter-ALTO communication.

Z. Duliński, R. Stankiewicz, P. Wydrych, M. Kantor, and P. Chołda, “Cost-driven peer rating algorithm,” in Proc. IEEE Int Communications (ICC) Conf, Kyoto, Japan, Jun. 2011. ©IEEE, available on IEEE Xplore.

The paper presents a concept of a rating algorithm aiming at overall peer-to-peer traffic reduction (and locality awareness) and decrease of load on costly links, thus diminishing operator’s costs. The rating algorithm is not only performed by a sole Oracle, as is typically proposed, but its operation is also supported by a similar entity located in other domains. Due to this concept, a usually omitted fact that the inter-domain routes are asymmetrical is properly dealt with. Simulations performed on a real topology show the usefulness of the presented approach.

P. Wydrych and P. Chołda, “ISP-supported traffic reduction for application-level multicast,” (presentation) in Proc. IEEE Int Communications (ICC) Conf, Kyoto, Japan, Jun. 2011. ©IEEE, available on IEEE Xplore.

The paper proves that it is possible to optimize application-level multicast operation from the viewpoint of traffic flows. A modification of the FreePastry/Scribe application is proposed to enable cooperation with the IETF ALTO (Application- Layer Traffic Optimization) protocol. Consequently, the overlay topology is constructed taking into account the underlying network topology. The presented results show that costly traffic types can be reduced while the increase of the delay is not harmful.

Z. Duliński, P. Wydrych, R. Stankiewicz, P. Chołda, and M. Kantor, “Inter-ALTO communication problem statement,” Internet Engineering Task Force, Internet-Draft draft-dulinski-alto-inter-problem-statement-00, Mar. 2011, work in progress.

This draft considers an approach to the optimization of the traffic generated by the overlay (peer-to-peer) applications, where some information on inter-AS (Autonomous System) paths is obtained with the usage of dedicated communication scheme known as inter-ALTO communication.

The large amount of network traffic generated by overlay applications requires effective management. This traffic traverses inter-AS links and thus generates substantial costs for the operators and poses problems with overload on the external and internal links. The traffic is not time-stable as the peers connect and disconnect very often. Additionally, when the overlay traffic is observed on inter-AS links, it can be seen that sources and destinations change in a very short period of time. The ALTO (Application-Layer Traffic Optimization) service provides the information that enables more efficient management of the overlay traffic. Such applications can use the information to perform better-than-random peer selection. The ALTO servers are responsible for a pre-selection procedure; the final selection is done by overlay clients and then the ALTO protocol conveys network information to applications. To be credible, this information should be as close to real network situation as possible. However, some types of data are not hold by an operator, but they should be gained on the basis of the additional information exchange with other AS operators. This document presents rationale for the need of introduction of the inter-ALTO communication.

Z. Duliński, R. Stankiewicz, P. Chołda, P. Wydrych, and B. Stiller, “Inter-ALTO communication protocol,” Internet Engineering Task Force, Internet-Draft draft-dulinski-alto-inter-alto-protocol-00, Jun. 2010, work in progress.

The ALTO service provides the information, which can make communication between applications more efficient, especially in case of overlay applications. Such applications can use the information to perform better-than-random peer selection. The ALTO protocol conveys network information to applications. The protocol definition of this document extends the functionality of this ALTO service by introducing a standardized manner of communications between ALTO servers. A new inter-ALTO protocol is proposed, which enables the exchange of information between ALTO servers. The servers can coordinate actions and can introduce policies, which provide communication between applications localized in cooperating Autonomous Systems with a higher performance and a better cost efficiency.

P. Wydrych, “Analysis of practical issues related to routing in overlay networks,” Master’s thesis, Department of Telecommunications, AGH University of Science and Technology, Kraków, Poland, Sep. 2009.

Since the introduction of Napster in 1999, many peer-to-peer (P2P) systems have been designed. In the beginning they were used for file-sharing, but then the ideas developed during the research of file-sharing overlay systems were employed in other fields. The application-level multicast (ALM) systems became an important alternative to client-server streaming and IP multicast. Since the peer-to-peer client applications became very popular and they build their structures without taking into account the underlying network topology, they cause the enormous percentage of the inter-domain traffic. Therefore, the idea of cooperation of peer-to-peer application users and network operators have emerged. At the time of writing, the research on the P2P-ISP collaboration focuses on the optimisation of the traffic generated by unstructured file-sharing systems.

This thesis proves that the solutions developed by the ALTO group can be successfully employed to reduce the traffic generated by the application-level multicast systems built on top of structured overlay networks.