Qos Overview; Qos Service Models; Best-Effort Service Model; Intserv Model - HP MSR4080 Configuration Manual

QoS overview

In data communications, Quality of Service (QoS) provides differentiated service guarantees for
diversified traffic in terms of bandwidth, delay, jitter, and drop rate, all of which can affect QoS.
QoS manages network resources and prioritizes traffic to balance system resources.
The following section describes typical QoS service models and widely used QoS techniques.

QoS service models

This section describes several typical QoS service models.

Best-effort service model

The best-effort model is a single-service model. The best-effort model is not as reliable as other models
and does not guarantee delay-free delivery.
The best-effort service model is the default model for the Internet and applies to most network
applications. It uses the First In First Out (FIFO) queuing mechanism.

IntServ model

The integrated service (IntServ) model is a multiple-service model that can accommodate diverse QoS
requirements. This service model provides the most granularly differentiated QoS by identifying and
guaranteeing definite QoS for each data flow.
In the IntServ model, an application must request service from the network before it sends data. IntServ
signals the service request with the RSVP. All nodes receiving the request reserve resources as requested
and maintain state information for the application flow. For more information about RSVP, see MPLS
Configuration Guide.
The IntServ model demands high storage and processing capabilities because it requires all nodes along
the transmission path to maintain resource state information for each flow. This model is suitable for
small-sized or edge networks, but not large-sized networks, for example, the core layer of the Internet,
where billions of flows are present.

DiffServ model

The differentiated service (DiffServ) model is a multiple-service model that can meet diverse QoS
requirements. It is easy to implement and extend. DiffServ does not signal the network to reserve
resources before sending data, as IntServ does.

QoS techniques overview

The QoS techniques include the following functions:
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