Ing. Ján Kučerák

he article describes our new SIP protocol implementation for the OMNeT++ simulation framework. OMNeT++ simulation framework provides an extensive support of IP related protocols, nevertheless a working SIP protocol implementation is missing. Real measurements were also done using a SIPp traffic generator and the results are compared to those obtained by our new SIP model. Since this work is a part of bigger project concerned strictly on measuring "first response times" over networks with a faulty transmission links, the actually collected statistics are focused only this way.

The response time critical application is defined as an application which misbehaves if a certain delay of communication is reached. Generally accepted example of such application is VoIP communication. This article focuses on the current IP transport layer protocols, i.e. TCP, UDP and SCTP and their suitability for real time signaling transport. Each protocol deals differently with the problem of delay and packet loss. In this paper the behavior of the protocols is compared under various delay and packet loss conditions. A simulation model in OMNET++ was prepared to and also the real tests were run on a special one purpose application to compare the behavior of living Linux implementation of these protocols.

The voice quality modelling assessment and planning field is deeply and widely theoretically and practically mastered for common voice communication systems, especially for the public fixed and mobile telephone networks including Next Generation Networks (NGN - internet protocol based networks). This article seeks to contribute voice quality modelling assessment and planning for dispatching communication systems based on Internet Protocol (IP) and private radio networks. The network plan, correction in E-model calculation and default values for the model are presented and discussed.

Viber is a proprietary communication protocol growing in popularity, on mobile devices especially. It represents a trend of replacing traditional protocols with proprietary messaging applications, employing cloud infrastructure support. It also constitutes a challenge to the networking community due to its unknown properties and opaque and highly distributed nature. We present observations-based analysis of the protocol function, topology, communication patterns and vulnerabilities, derived from traffic captures by simple data mining.

This paper discusses SIP interoperability in mixed IPv4/IPv6 environments. Legacy Ipv4 client devices and IPv6 drive will make operators to seek a gentle transition from IPv4 to IPv6. Paper provides detailed description of SIP and SDP signaling manipulation to be done by a SIP/RTP proxy to bridge IPv4 and IPv6 networks correctly allowing pure IPv4 (non-dual stack) devices to reach IPv6 terminations (and vice versa) just by their AOR(Address-of record).

This article disserts on an IMS network and its structure and analyses signalizations during connection between end use devices. Furthermore, the article deals with roaming issue and IMS networks.

Concern of this paper is to reveal advantages offered by usage of open source products in education process. This advantages will be demonstrated on one concrete system used by author.