In Voice over IP, the quality of interactive conversation is important to users. Major factors affecting perceived quality are delay, delay jitter, and missing packets. For conversational VoIP, a conversational delay also plays an important role for perceived quality. Large conversational delay can result in double talk, echo or even the termination of the conversation. In practice, a playout b...

Voice over IP (VOIP) the transmis­ sion of voice over traditional packetswitched IP networks is one of the hottest trends in telecommunications. As with any new technology, VOIP introduces both opportunities and security challenges. Lower cost and greater flexibility are among the prom­ ises of VOIP for the enterprise, but security administrators will face signif­ icant issues. Administrators m...

With the tremendous growth in popularity and bandwidth of the Internet, VoIP technology has emerged that allows phone calls to be routed over Internet infrastructure rather than the traditional Public Switched Telephone Network (PSTN) infrastructure. The issues faced by law enforcement authorities concerning VoIP are very different from that of traditional telephony. Wiretapping is not applicab...

The functional and cost advantages of Internet telephony are evident. By today's technical standards, however, Voice Over IP (VoIP) is still less secure than traditional telephony. At the same time, the hacker scene is constantly looking for new weak spots and developing ingenious methods of attack to gain access to confidential information and penetrate further into the network.

Voice signalling protocols have evolved, keeping with the prevalent move from circuit to packet switched networks. Standardization bodies have provided solutions for carrying voice traffic over packet networks while the main manufacturers are already providing products in workgroup, enterprise, or operator portfolio. This trend will accrue in next years due to the evolution of UMTS mobile netwo...

Users of Internet telephony applications demand good quality audio playback. This quality is largely dependent on the instantaneous network conditions as well as both the time and day. Equally, if not more important, is the reliability of using the Internet for voice communication. Calls that cannot be completed are unacceptable for all users. In this paper we describe a scheme for measuring ne...

Voice-over-IP (VoIP) has become an attractive alternative to the plain old telephone system, especially due to the much lower communication costs. However, there are several threats. In this document, several such threats are discussed. Moreover, we ask whether these systems could be used in environments with very high security demands as they for example exist in the Swiss army. ∗Computer Syst...

The fast spread of handheld smart devices contributed to the development of VoIP softphones running over such devices. Most security mechanisms were mainly designed for desktop PCs and hence did not take into consideration the power constraints of handheld devices. This fact highly motivated the development of new security mechanisms that try to minimize the energy consumption without compromis...

This paper presents a dynamic Service Level Agreement (SLA) negotiation scheme between peer autonomous systems (ASes) that implement DiffServ per domain behaviors. For concreteness, we tailor our scheme to account for the needs of VoIP transport across multiple ASes. We present a heuristic but computationally simple and distributed scheme that uses traffic statistics to forecast the near-future...

Zusammenfassung: Die Umstellung der klassischen leitungsgebundenen Telefontechnik auf eine moderne und auf längere Sicht kostengünstigere Voice over IP Infrastruktur rückt zunehmend ins Blickfeld der Entscheidungsträger in mittleren und größeren Unternehmen. Doch ein unter Umständen hoher Integrationsund Administrationssaufwand bleibt bei den bisher angebotenen Lösungen auf Basis von H.323 und ...