SAUSEN, P. S.; http://lattes.cnpq.br/5358851504202129; SAUSEN, Paulo Sérgio.
Resumo:
This present work analyses the mechanisms of flow control for ABR services on
ATM networks. The aim of ABR service is to adjust the transmission rate of the cells, directly
onto the data source, owing to the charge condicion of the network.
On ABR service, the ATM switch may adopt two different mechanisms - the binary
mechanism and the ER (Explicit Rate) one. Under the binary mechanism soon after detecting
the congestion, the switch will mark every cell which passes by, as congested one, having
the source to accomplish the procedure of transmission rate reduction. On the ER mechanism,
which shows several varations, the ATM switch is able to broadcast the network
traffic and calculate the transmission rate which can be tolerated by the network and, subsequently,
inform this rate to the source through the RM cells (Resource Management).
In this work the binary flow control mechanism EFCI (Explicit Forward Congestion
Indication) and two ER mechanisms - the EPRCA (Enhaced Proportional Rate Control Algoritm)
and NIST ER, are discussed. These mechanism were simulated and their results
were analysed and compared. A shareware version of the NIST ATM was used as a simultion
tool. The following performance measurements are shown on regards to time: ACR
(Allowed Cell Rate), buffer occupation and link utilization. Other measurements such as
average value of ACR, throughput and fairness, are also shown. The fairness measurement
allows to verify how fair the simulated mechanisms are in bandwidth allocation.