QoS for Network Aplications

QoS: “la red provee a la aplicación
el nivel de performance
necesario para funcionar
correctamente.”

Principle 1: Packet classification allows a router to distinguish among packets belonging to different classes of traffic.

Principle 2: It is desirable to provide a degree of isolation among traffic flows, so that one flow is not adversely affected by another misbehaving flow.

Principle 3: While providing isolation among flows, it is desirable to use resources (e.g., link bandwidth and buffers) as efficiently as possible. High resource utilization.

Principle 4: A call admission process is needed in which flows declare their QoS requirements and are then either admitted to the network (at the required QoS) or blocked from the network (if the required QoS can not be provided by the network).

Mecanismos de Scheduling & Policing

1) Scheduling:Eleccion del proximo paquete

FIFO – descarta si ante un arribo la cola esta llena.

Priority – multiples clases, con prioridades diferentes.

Round-Robin – turnos en las colas de cada clase.

WFQ: Weighted Fair Queuing - Round Robin generalizado.

2) Policing: limitar el trafico para que no exceda los parametros acordados

Average Rate – paquetes por unidad de tiempo.

Peak Rate – promedio pico.

Burst Size – maxima cantidad de paquetes enviados consecutivamente.

Token Bucket: limitar la entrada a Burst Size y Average Rate especificados.

TB & WFQ:  garantizar QoS. Garantizar una cota superior en el retardo.