Abstract 

The demand of Quality of Service (QoS) and real-time channels on computer 
networks has recently increased due to the development of new multimedia applications. 

This multimedia transmission requires a very demanding reservation of network 
resources. This is due mainly to the traffic characteristics and the quality of service the 
applications require. 

This transmission is usually done using a channel. Channel establishment requires 
reserving some network resources (bandwidth and buffers) in order to implement the real-
time channel. This reservation mainly depends on traffic characteristics, but also on 
network parameters. 

Multimedia traffic usually has a very variable transmission rate (VBR). That 
implies that in order to guarantee the quality of service, the reservation of network 
resources is very high. However, these resources are usually misused when transmission 
rate is low. 

Therefore, the optimisation of network resources is a key issue. There is a need for 
methods that obtain the optimal reservation of network resources which guarantee quality 
of service. These methods must be efficient enough in order to be used on-line 

In this dissertation, some new schemes to save network resources are introduced. 
The first method is based on generating a set of points from the stored video with an offline 
analysis of its empirical envelope, and then using these points to efficiently calculate 
the optimal bandwidth reservation for a given channel, at channel establishment time. 
These points are used to optimise the buffer node. In both cases, a leaky or token bucket 
flow specification is used. Finally, a new scheme for fault detection for highly available 
real-time channels is developed. This new scheme provides an efficient resource 
reservation and it is based on “suspecting” a failure when the packet delay through the 
primary channel is close to the maximum guaranteed delay. Theses schemes have been 
proved using MPEG traffic traces.