Details of Grant 

EPSRC Reference:	GR/K35365/01
Title:	ROPA: DIAGNOSIS OF CONGESTION IN ATM NETWORKS
Principal Investigator:	Linington, Professor PF
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Sch of Computing
Organisation:	University of Kent
Scheme:	ROPA
Starts:	01 March 1995	Ends:	30 November 1998	Value (£):	115,128
EPSRC Research Topic Classifications:	Networks & Distributed Systems
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:
Summary on Grant Application Form
In Asynchronous Transfer Mode networks, reliability depends on the avoidance of local congestion. The project will study the way in which the timing characteristics of ATM cell streams are modified by their passage through switches. The aim is to use such timing information for traffic analysis and fault diagnosis in operational networks. This requires:a) techniques for collecting data on performance and traffic distributions in real networks;b) tools which use this data to analyse the causes of congestion in the networks.Progress:Previous work at Kent on the simulation of traffic flows through networks of ATM switches has demonstrated useful self stabilising properties when traffic streams compete repeatedly for link capacity, and has shown that, when considering uniformly loaded networks, particular switch architectures each have a characteristic signature which colours the traffic distribution they switch. This signature can be seen most clearly in the autocorrelation function of a traffic stream. Mr G.E.W.Tripp has designed and built an ATM interface which provides powerful facilities for the measurement and generation of traffic patterns in ATM LANs, allowing cells to be transmitted or traffic recorded at up to 100Mbps with a cell timing accuracy of +40 nanoseconds. This equipment is now in operation and is being used to investigate the properties of different ATM switches, starting with an HP Laboratories Sapphire switch. Once these initial investigations using known traffic distributions have been completed, the investigation of traffic in operational networks will begin. The basic approach proposed is to compare the traffic distribution on one or more test streams at two different points in the network, thus obtaining information on the behaviour of the switches traversed between the observation points. Monitoring units will be inserted into the network links so that they can observe cells passing. To simplify this activity, the interface is being repackaged as the basis of a portable, free-standing monitor, which will be configured to relay ATM cells without change. These units will be inserted into one of the directions of flow of appropriate target ATM links. The various sets of observations will be preprocessed and timing data returned via the ATM network to a suitable control point. An analysis process at this control point will then compute a cross-correlation function, and interpret it to identify both the level ofcompetition experienced by the stream being investigated and, more importantly, total loading or congestion measures for the switches along the route. This project has only just begun; the investigators aim to have practical diagnostic tools available at a time when ATM LAN traffic will be growing rapidly and unexplained and unexpected traffic management phenomena are likely to be making their appearance and will need to be investigated.
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Organisation Website:	http://www.kent.ac.uk