Real-time traffic in Internet is growing and the best-effort model has
not been designed for such challenging streams. The DiffServ
(DS) architecture, which permits to aggregate traffic flows into
classes with a common forwarding requirement, is a Quality of service
(QoS) solution for IP networks. But most of the DS models provide
classes getting better performance than others, calling for pricing
differentiation and possibly admission control. We explore the
possibility of providing a simple, robust and pricing-free QoS
solution by practicing "differentiated fairness": different
classes have equivalent performance according to their specific
needs. No admission control is required, no absolute guarantee is
provided. This "soft" model has been implemented as a Linux
kernel queuing discipline and succesfully tested over a cluster of
PCs.
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