This paper presents a method for admitting voice calls in Telephony over IP (ToIP) scenarios. This method, called QoS-Weighted CAC, aims to guarantee Quality of Service to telephony applications. We use a measurement-based call admission control algorithm, which detects network congested links through a feedback on overall link utilization. This feedback is based on the measures of packet deliv...

Computer telephony integration (CTI) is a term to which many are becoming accustomed. It encompasses an entire industry, devoted to the closer integration of telephony systems with computer-control devices, as well as an everexpanding range of applications. At the forefront of this industry are innovative products, built using hardware able to terminate digital telephony tier 1 (T1) and E1 (T1 ...

As the telegram was replaced by telephony, so to Voice over IP (VoIP) systems are replacing conventional switched wire telephone devices, these systems rely on Internet connectivity for the transmission of voice conversations. This paper is an outline of ongoing preliminary research into malfeasant VoIP activity on the Internet. 30 years ago PABX systems were compromised by hackers wanting to m...

The performance of IP telephony systems is highly dependent on the audio codecs and their reaction to packet loss and instantaneous delays. Understanding the interaction between audio encoding and the dynamic behavior of the Internet is significant for designing adaptive audio transport mechanisms. For this purpose, we conducted a large-scale audio transmission experiment over the Internet in a...

Voice communications on IP networks use owner protocols as well as standards like SIP, MGCP and H323. In this paper we propose a new method for transparent traversal of NATed (Network Address Translated) networks for the SIP (Session Initiation Protocol) protocol. Although SIP is an application layer protocol, its operation is affected by address translation. This is because SIP uses network la...

Multimedia communications over IP are booming as they offer higher flexibility and more features than traditional voice and video services. IP telephony known as Voice over IP (VoIP) is one of the commercially most important emerging trends in multimedia communications over IP. Due to the flexibility and descriptive power, the Session Initiation Protocol (SIP) is becoming the root of many sessi...

The typical approach to steganography is to compress the covert data in order to limit its size, which is reasonable in the context of a limited steganographic bandwidth. TranSteg (Trancoding Steganography) is a new IP telephony steganographic method that was recently proposed that offers high steganographic bandwidth while retaining good voice quality. In TranSteg, compression of the overt dat...

IP telephony is less confined than traditional PSTN telephony. As a consequence, it is more exposed to security attacks. These attacks are specific to VoIP protocols such as SPIT, or are inherited from the IP layer such as ARP poisoning. Protection mechanisms are often available, but they may seriously impact on the quality of service of such critical environments. We propose to exploit and aut...

Next generation wireless networks will rely heavily on packet transport for both data and voice services. In this paper, we describe the Router for Integrated Mobile Access (RIMA) system, which is the core network element of an integrated wireless packet network. RIMA acts as a Mobile Switching Center for standard cellular telephony users, and a mobile router for wireless packet data users. RIM...

If quality of service could be provided at the transport or the application layer, then it might be deployed simply by software upgrades, instead of requiring a complete upgrade of the network infrastructure. In this paper, we propose a self-admission control scheme that does not require any network support or external monitoring schemes. We apply the admission control scheme to IP telephony as...