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Getting Educational Systems Talking Across Leading-Edge Technologies

UoS' Testbed

Network evaluation of the GESTALT application will be supported by the GESTALT Quality of Service (QoS) Testbed, called Ghost. Ghost is a further development of the Testbed from the RENAISSANCE project (AC100). Ghost is to be used to determine how the GESTALT application behaves with respect to QoS when run across mixed network technologies. The aims is to assess how can QoS definition encapsulated in the metadata representation be used by the network to provide the requested QoS.

Evaluation Scenarios

The scenarios selected for the network evaluation of the Gestalt application are:

a) Is the architecture latency or bandwidth limited?

If bandwidth limited, at which point must more bandwidth be supplied
If latency limited what is the cause (server, client, propagation, window size, internetwork device latency or network access);

b) How many simultaneous users can access the service;
c) The effects on the performance created by mixed network technologies i.e. Fast Ethernet and cable modem.

Technical Approach

The network performance evaluation will assess how the QoS definition in the metadata representation can be used by the network to ensure the provision of the necessary QoS. The tests to be conducted in Ghost aim to:

Validate the provision of QoS across Ethernet and Cable TV (CATV) networks. The CATV equipment will be Bay Networks and Multimedia Cable Network Systems Data Over Cable Service Interface Specification (MCNS DOCSIS) compliant cable modems;
Validate the Gestalt application over Internet Protocol version 4 (IPv4) networks with and without QoS support. RSVP signalling will be used on the QoS capable routers;
Investigate the effects of background load increase on Constant Bit Rate (CBR) streams and how QoS is influenced;
Propose solution for the load balancing on a saturated up stream CATV channel to support QoS;
Investigate compatibility issues between MCNSv1.1 QoS and Integrated Services (RSVP) QoS;
Investigate how the network based QoS definitions can be incorporated into the metadata representations and how these generic definitions can be interpreted by each particular network technology.

Test Schedules

The Gestalt application will be tested across IPv4 networks. The test schedule selected are:

a) Fast Ethernet without background load

With Best effort Routers
With RSVP enabled Routers

b) The above experiments with background load on the server site and the intermediate link

c) CATV without background load

With Best effort Routers
With RSVP enabled Routers

d) The above experiments with background load on the server site, the intermediate link, the cable modems and the headend.

The test and measurement tools

Ghost will use the following test and measurement tools to evaluate the network performance of the gestalt application:

Expert Sniffer network analyser – the protocol monitor and decoder for use on Ethernet and CATV;

SmartBits load generator – the layer two and three packet traffic generator for Ethernet and CATV;

PC based tools – PC tools used to measure events on the network (NetXRay, TCPWins32 ).

Updated 13-OCT-1999

Send comments or questions to kriley@fdgroup.co.uk