Manuel Görtz

RSVP as firewall signalling protocol

Within a global networked environment, security aspects have become more and more important and access control at network borders is considered essential. For this purpose firewall systems are used which provide a well-established security mechanism to restrict the exchanged traffic to a certain subset of users and applications. In order to cope with the increasing demand for new applications, a firewall must be flexible and extensible to support such new applications and their protocols. RSVP is a dynamic signalling protocol, which has been invented to negotiate resource requirements between end systems and a packet-based communication network. We investigate the interoperation of RSVP with a firewall system in order to support new applications in a generic way. We show how the resulting system flexibility allows for a variety of employment scenarios and incremental deployment of such a technology. We back up our claims by describing a prototype that we have implemented.

Enhanced SIP communication services by context sharing

Communication plays a central in our society. It affects our private lives as well as business activities. Humans usually observe the environment and the communication partner with all their senses. The perceived information is evaluated to deduce the context of the targeted communication partner. However, distant interpersonal communication does not provide a priori knowledge of the called partys current situation, condition or mood - the callees context. Current communication systems do not offer satisfying technical means to support context sharing between communication partners. The proposed solution in This work is based on an enhancement of the session initiation protocol (SIP) for IP telephony systems. Different mechanism of sharing context among communication peers have been investigated, implemented and evaluated.

The Digital Call Assistant: Determine Optimal Time Slots for Calls

Communication plays a key role in today’s businesses. Reaching a communication partner often has become a time consuming task. A multitude of potential communication channels with individual addresses forces a callee to guess an appropriate device at the right time. Under these circumstances additional information about a high probability to reach the calling target at a specific point in time enhances efficiency in communication. The decision when to call and the choice of the communication channel can be based on these information. This paper presents a Digital Call Assistant to determine an optimal time slot to place a call. The proposed approach combines calendar events and context information. The combination of these two information sources allows the creation of call plans which provide a list of possible time slots for communication with another user. A trust concept will assure that these sensible data will only be shared among trusted peers. Pending call requests and open call slots are presented to the user. The proposed planning application is going to form a novel part in our context-aware communication service framework.

Using Context Information to Avoid Service Interactions in IP Telephony

IP Telephony is an important application for building integrated communication services on IP networks. It provides telephony functionality similar to the Plain Old Telephone System. A rich variety of novel multimedia services is expected to augment the basic call functionality of IP Telephony systems. These services make the use of IP Telephony very attractive. However, multimedia services are much more complex than plain telephony services. IP-based telephony solutions are expected to be operated in a deregulated market where many different parties develop and deploy their own services. The conflicts and interactions that result from this practice make this application area challenging on a technical but also on an operational level.

Using a multi-layer approach to tackle the service interaction problem in telephony scenarios

The inauguration of IP telephony as a new and promising technology has opened the door to a variety of enhanced communication services and applications, which differ from those of the PSTN. The shift from circuit switched to packet-based networks, from a central to a more decentral organization, from professional and vendor driven development to an open development environment enables a multitude of opportunities. A variety of tools and methods for service creation has been developed to ease the process of design and implementing services. But these new freedoms hold new risks (well known from the PSTN area), which are currently not in the main focus of standardization. The rising problem can be overcome by the use of formal methods and checks which also tackle the important problem of feature interaction. In this paper we present a multilayer concept using a mixture of formal and informal techniques like service pattern to approach this topic.