Ein Datenakquisitionssystem für passive Messungen in Telekommunikationsnetzwerken

Celland packet-oriented broadband telecommunication networks such as Asynchronous Transfer Mode (ATM) differ substantially from weIl known telephony networks. The data rates in the synchronous digital hierarchy (SDH) are much higher than in the plesiochronous hierarchy (PDH), and with the rise of new applications and access technologies the traffic profiles have changed. Furthermore, the intelligent network functions, e.g. connection control, have been shifted into the terminal equipment. The measurement of nerwork traffic is a very important task for the understanding of the characteristics of the traffic transported on broadband telecommunication networks. This knowledge is crucial to the design and operation of a network. For this purpose advanced measurement systems are required. The monitoring of the quality of service and the collection of trafflc profiles for network engineering are important tasks, which must be supported by measurement systems. In addition, measurement methods with artificially produced data streams are no longer sufficient. Rather it is necessary to measure the real nerwork traflic. This measuring methodology, called passive measurement, requires the processing and storage ofvery large data sets at very high data rates. In order to fulfil these requirements, an acquisition system for ATM networks called AKQUI is presented in this thesis. The system allows the recording of large network streams over a long period of time. In a first step, a high resolution and accurate timestamp is added to each cell, After that, the cells are transferred in larger data units to a RAID subsystem. The analysis of the recorded trafflc is typically performed offline with a workstation, Since the internet is used as a communication link between the workstation and the AKQUI system, it is possible to control the measurement and analyse the network traffic from everywhere. In addition to the implementation of the AKQUI systern, the functional units of such a measuring system are systematically examined. Based on this analysis, the critical points of the functional units are discussed and different system architectures are developed. This analysis of the functional units is to a large extent also applicable to all data acquisition systems for passive measurements. The presented acquisition system differs from other implementations by the fact that the entire data path of the AKQUI measurement system is designed for the maximum data rate of a STM-1I0C-3 network link. Data reduction procedures, whieh are often necessary due to bottlenecks in the data path, are not necessary in the presented system. This opens extended possibilities for the analysis of the recorded traffic. Different measurement campaigns in experimental and productive telecommunication networks have been carried out using the AKQUI system. It has been shown, that aceess to the entire traffie payload enables extended analysis of different protocol layers over very long measurement periods.