2024-03-29T05:28:06Zhttps://www.tdx.cat/oai/requestoai:www.tdx.cat:10803/77152017-09-22T14:01:42Zcom_10803_253col_10803_263
nam a 5i 4500
Convolucions (Matemàtica)
Modalidad de transferencia asíncrona
Convolution (Mathematic)
Asynchronous transfer mode
Modalitat de transferència asíncrona
Convoluciones (Matemática)
Enhanced convolution approach for CAC in ATM networks, an analytical study and implementation
[Girona] :
Universitat de Girona,
2011
Accés lliure
http://hdl.handle.net/10803/7715
cr |||||||||||
AAMMDDs2011 sp ||||fsm||||0|| 0 eng|c
8484581063
Marzo i Lázaro, Josep Lluís,
autor
Tesi
Doctorat
Universitat de Girona. Departament d'Electrònica, Informàtica i Automàtica
1997
Universitat de Girona. Departament d'Electrònica, Informàtica i Automàtica
Tesis i dissertacions electròniques
Domingo Pascual, Jordi,
supervisor acadèmic
Batlle i Grabulosa, Joan,
supervisor acadèmic
TDX
The characteristics of service independence and flexibility of ATM networks make the control problems of such networks very critical. One of the main challenges in ATM networks is to design traffic control mechanisms that enable both economically efficient use of the network resources and desired quality of service to higher layer applications. Window flow control mechanisms of traditional packet switched networks are not well suited to real time services, at the speeds envisaged for the future networks. <br/>In this work, the utilisation of the Probability of Congestion (PC) as a bandwidth decision parameter is presented. The validity of PC utilisation is compared with QOS parameters in buffer-less environments when only the cell loss ratio (CLR) parameter is relevant. The convolution algorithm is a good solution for CAC in ATM networks with small buffers. If the source characteristics are known, the actual CLR can be very well estimated. Furthermore, this estimation is always conservative, allowing the retention of the network performance guarantees. <br/>Several experiments have been carried out and investigated to explain the deviation between the proposed method and the simulation. Time parameters for burst length and different buffer sizes have been considered. Experiments to confine the limits of the burst length with respect to the buffer size conclude that a minimum buffer size is necessary to achieve adequate cell contention. Note that propagation delay is a no dismiss limit for long distance and interactive communications, then small buffer must be used in order to minimise delay. <br/>Under previous premises, the convolution approach is the most accurate method used in bandwidth allocation. This method gives enough accuracy in both homogeneous and heterogeneous networks. But, the convolution approach has a considerable computation cost and a high number of accumulated calculations. <br/>To overcome this drawbacks, a new method of evaluation is analysed: the Enhanced Convolution <br/>Approach (ECA). In ECA, traffic is grouped in classes of identical parameters. By using the multinomial distribution function instead of the formula-based convolution, a partial state corresponding to each class of traffic is obtained. Finally, the global state probabilities are evaluated by multi-convolution of the partial results. This method avoids accumulated calculations and saves storage requirements, specially in complex scenarios. <br/>Sorting is the dominant factor for the formula-based convolution, whereas cost evaluation is the dominant factor for the enhanced convolution. A set of cut-off mechanisms are introduced to reduce the complexity of the ECA evaluation. The ECA also computes the CLR for each j-class of <br/>traffic (CLRj), an expression for the CLRj evaluation is also presented. <br/>We can conclude that by combining the ECA method with cut-off mechanisms, utilisation of ECA in real-time CAC environments as a single level scheme is always possible.
g
ES-BaCBU
cat
rda
ES-BaCBU
text
txt
rdacontent
informàtic
c
rdamedia
recurs en línia
cr
rdacarrier