Constantin Werner

A UML profile for communicating systems

This paper presents a UML 2 profile for communicating systems. It is driven by the experience of SDL and uses formal constraints for profile definition and mapping rules by means of OCL. It features language elements for high-level specification and description of Internet communication and signaling protocols where SDL is not optimally suited. Due to its support of several concrete notations, this profile is aligned to work with several UML 2 compliant modeling tools. In addition, an implementation by an XSLT-based mapping from UML to behavioral and structural SDL specifications is available. The intention of the paper is to present the main work done which is defining an actual profile and mapping this to SDL.

Modeling route change in soft-state signaling protocols using SDL: a case of RSVP

Soft state signaling protocols install and maintain states in network nodes, expiring without receiving refreshes. These states require proper reparation when the flow path changes, especially in case of link or node failures. As the specifications usually do not describe in detail how to handle these failures, we present insights by developing SDL models for RSVP on this issue.

Fast Re-Authentication for Inter-Domain Handover using Context Transfer

The exponential growth of wireless mobile systems in recent years has created strong demand to handover between different administration domains. Such movement suffers from limited resources such as limited bandwidth and high latency. Furthermore, authentication is the key factor when providing mobile roaming services, so fast re-authentication is one of the important issues to achieve a short overall handover delay. Therefore, it is important to develop techniques that utilize the available bandwidth efficiently. One way of utilizing the wireless resources efficiently is by transferring the required context that authenticates the user in new visited domain of the running session rather than establishing the connection from scratch. Current approaches only consider a repeated authentication process run for a new visited domain and therefore, can potentially introduce high latency by communicating with authorization services of a home domain. In this paper, we propose a novel way to authenticate a mobile node without the necessity to communicate with the home domain while maintaining a high level of security. We provide an overview of the method, show the improvement to related approaches in terms of message flows and discuss security aspects.

Enabling Pervasiveness by Seamless Inter-domain Handover: Performance Study of PANA Pre-authentication

Pervasive wireless networking requires continuous connection to the Internet while moving from one administration domain to another. To enable continuous connection seamless handover has to be ensured. A concept to ensure seamless handover is the make-before-break approach which can be achieved by performing the pre-authentication in the new domain while maintaining connection to current domain. The duration of the authentication is critical for the handover process because if the mobile nodes move very fast the remaining amount of time of connection to the current domain can become very limited. Therefore, it is a vital issue for seamless mobility to study the authentication performance of a pre-authentication framework. In this paper we model an authentication infrastructure and consider a scenario in which a high number of nodes handover to a new administration domain. The simulation of the authentication process shows the relation between authentication performance and traffic intensity. Furthermore we identify some critical points and potential bottlenecks of this pre-authentication approach.

Performance Evaluation of PANA Pre-authentication and PANA Context Transfer

The future vision of the wireless networks is coexistence of current existing access networks. The different access networks managed by different operators will be bound together into a single network and the Internet Protocol will be the glue. To fulfill this vision, one of the most challenging parts is to facilitate the authentication phase of the handovers between domains. PANA pre-authentication scheme was designed to carry the authentication information before the actual handover execution from one domain to a subsequent domain. However, the available time to complete this handover can be rather short due to the users movement. In this paper, a new approach is presented that can substantially lower the time needed for an inter-domain handover by using context transfer compared to PANA pre-authentication. We describe the approach and show its benefits by means of simulation using the tool OMNET++.

Performance Study of PANA Pre-authentication for Interdomain Handover

To provide seamless mobility to the wireless user, a continuous connection to the Internet is required while moving from one administration domain to another. To enable continuous connectivity, one prerequisite is the incorporation of seamless handover. The make-before-break approach facilitates seamless handover by means of executing an authentication to a new domain simultaneously while maintaining connection to current domain. The connection is only terminated after the handover to the new domain is successfully completed. However, the duration of the authentication is critical for the handover process because if the mobile nodes move very fast the remaining amount of time of connection to the current domain can become very limited. Therefore, it is a vital issue for seamless mobility to study the authentication performance of a pre-authentication framework. In this paper we model an authentication infrastructure and consider a scenario in which a high number of nodes handover to a new administration domain. The simulation of the authentication process shows the relation between authentication performance and traffic intensity. Furthermore we identify some critical points and potential bottlenecks of this pre-authentication approach.

An Evaluation of Multi-Role Access Routers Specification and Validation of an IDKE aware Access Router

The inter domain key exchange protocol (IDKE) is a newly developed approach to forward credentials between access routers. The IDKE protocol utilizes an IP based infrastructure to transfer a session-key due to mobile handover. This paper presents an SDL model of the IDKE protocol aware access router particularly with respect to robustness to multiple concurrent and non-sequential mobile initiated handovers. This paper will show how an access router is able to detect and handle these events