Józef Lubacz

LACK--a VoIP steganographic method

The paper presents a new steganographic method called LACK (Lost Audio PaCKets Steganography) which is intended mainly for VoIP. The method is presented in a broader context of network steganography and of VoIP steganography in particular. The analytical results presented in the paper concern the influence of LACK’s hidden data insertion procedure on the method’s impact on quality of voice transmission and its resistance to steganalysis.

Principles and overview of network steganography

The article discusses basic principles of network steganography, which is a comparatively new research subject in the area of information hiding, followed by a concise overview and classification of network steganographic methods and techniques.

Saturation throughput analysis of IEEE 802.11g (ERP-OFDM) networks

This paper presents the saturation throughput analysis of IEEE 802.11g (ERP-OFDM) networks. The presented work is based on the Markov model previously introduced and validated by the authors in Szczypiorski and Lubacz (Lecture Notes in Computer Science, vol. 4516, pp. 1082–1093, Springer, [2007]). In the present paper the saturation throughput is evaluated in different channel conditions as a function of frame length.

Performance evaluation of IEEE 802.11 DCF networks

The paper presents a new analytical saturation throughput model of IEEE 802.11 DCF (Distributed Coordination Function) with basic access in ad-hoc mode. The model takes into account freezing of the backoff timer when a station senses a busy channel. It is shown that taking into account this feature of DCF is important in modeling saturation throughput - yields more accurate results than models known from literature. The proposed analytical model also takes into account the effect of transmission errors.

On steganography in lost audio packets

This paper presents a new hidden data insertion procedure based on the estimated probability of the remaining time of the call for the steganographic method called lost audio packets (LACK) steganography. LACK provides hidden communication for real-time services such as voice over IP. The analytical results presented in this paper concern the influence of LACKs hidden data insertion procedures on the quality of voice transmission and the resistance to steganalysis. The proposed hidden data insertion procedure is also compared with previous steganogram insertion approaches on the basis of estimating the remaining average call duration. Copyright

Multi-layer aspects in modeling bandwidth trading

The paper discusses alternative approaches to introduce multi-layer relations between network resources in balancing demand and supply in a bandwidth market. Two multi-commodity double auction models have been presented with illustrative examples.

A systematic approach to network planning

The paper introduces a reference model for network planning activities. The planning process is conceptualised in terms of a trajectory—a sequence of elementary network planning problems-which traverses a three dimensional “planning space”. The “dimensions” of the space pertain to the time horizon of planning, to the type of network resources being planned (to a layered architecture of network resources) and to a set of generic network planning tasks. The model has been successfully exploited by the authors in real-world network planning projects, in the implementation of a comprehensive network planning software and also in academic courses.

Traffic routing in the Warsaw metropolitan network: a deployment strategy

The Warsaw metropolitan network is undergoing a radical architectural and technological transformation. The transformation, forced by the large unrealized demand for telephone stations, and structural traffic bottlenecks, is based on the installation of eight digital transit switches of high capacity. The so-formed upper transit layer gives an opportunity for the deployment of an efficient traffic routing system, for carrying the growing traffic well beyond the year 2000 without additional investments. A step-wise strategy is presented far the deployment of a modern traffic routing system in the Warsaw network, adapted to, and taking advantage of the fast transformation of the network. The choice of the strategy is based on a case study of the traffic handling efficiency of various routing systems in a model of the Warsaw metropolitan network. >

ISDN and new services in Poland: opportunities and obstacles

Presents an overview of problems involved in introducing ISDN and new services in the public network of Poland. The technical aspects of the assumed network and services development strategy are considered. The focus is on development alternatives and the process of establishing national requirements for the development. >