Christoph Egger

TU Wien | TU Wien

Last year's trend to migrate circuit-switched voice networks to packet switched Internet Protocol (IP) based networks has favored wide deployment of Session Initiation Protocol (SIP) based systems and networks. As a reaction to large-scale SIP deployment experiences in the field and the need to implement high availability and reliability within the...

Last year’s trend to migrate circuit-switched voice networks to packet switched Internet Protocol (IP) based networks has favored wide deployment of Session Initiation Protocol (SIP) based systems and networks. As a reaction to large-scale SIP deployment experiences in the field and the need to implement high availability and reliability within the...

The Session Initiation Protocol (SIP) relies on timer-based message retransmission for safeguarding reliable message transfer when deployed on top of the unreliable User Datagram Protocol (UDP) over IP. In this paper we present a detailed impact analysis of SIP timers onto the functionality of a system and its capabilities to recover from overload...

With the upcoming introduction of the Session Initiation Protocol to carrier grade telecommunication infrastructures, the threat of attacks is increasing massively. Multiple types of unsolicited communication, like high and low rate Denial-of-Service attacks as well as Spam over Internet Telephony driven by Botnets will be an upcoming risk for all...

We present sensing mechanisms that can be used for implicit high-load and overload detection in SIP networks. By means of measurements and simulations we highlight the characteristics of SIP proxy servers for different load situations and using different transport protocols. Each protocol yields to distinctive patterns that encourage deriving an al...

The 3GPP has chosen the Session Initiation Protocol (SIP) as signalling protocol for the IP Multimedia Subsystem (IMS); therefore, it is expected that telecom operators will widely use it for their systems. SIP relies on an underlying transport protocol, like, e.g., TCP, UDP or SCTP. In the case of UDP, SIP has to ensure itself that messages will b...

The 3GPP has chosen the Session Initiation Protocol as signalling protocol for the IP Multimedia Subsystem; therefore, it is expected that telecom operators will widely use it for their systems. SIP relies on an underlying transport protocol, like, e.g., TCP, UDP or SCTP. In the case of UDP, SIP has to ensure itself that messages will be reliably d...

Detecting overload in telecommunication networks is an important goal, because it allows to react on it and to reduce traffic smartly to ensure constant user experienced quality of service. This applies not only to media as voice and video, but also to signaling, which is responsible for setting up these media. An overloaded signaling network incre...

Cooperation in ad hoc networks cannot be taken for granted when nodes belong to distinct authoritative domains. In this paper we present Cashflow, a virtual currency system to motivate nodes to participate in ad hoc networks and to prevent selfishness. This system is different to previously proposed virtual currency systems in that it uses a channe...

Novel mobile cellular access network technologies like Long Term Evolution (LTE) promise capacities exceeding the ones of existing 3G networks by at least one order of magnitude. This evolution will enable the deployment of services which, due to their capacity requirements, are currently restricted to fixed access networks. On the other hand, pack...

SPIT is an upcoming threat for receiving unsolicited messages in Voice over IP systems. We assume, that future SPIT will be sent through the same infrastructure as SPAM today, namely through a network of compromised hosts. Therefore spammers will see SPIT as an additional business case. In this paper we show a viable way to increase the hit rate of...

Evaluating the user satisfaction with Next Generation Network applications requires, amongst others, to carefully study the impact of various access networks with differing performance characteristics. This paper presents the concept and implementation of a network emulator for IP-based packet-switched wired and wireless access technologies based o...