3Com WX3000 QoS Configuration, Introduction to QoS, Traditional Packet Forwarding Service

1 QoS Configuration

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The term switch used throughout this chapter refers to a switching device in a generic sense or the switching engine of the WX3000 series.

The sample output information in this manual was created on the WX3024. The output information on your device may vary.

Overview

Introduction to QoS

Quality of service (QoS) is a concept generally existing in occasions with service supply and demand. It evaluates the ability to meet the need of the customers in service. Generally, the evaluation is not to grade precisely. Its purpose is to analyze the conditions where the service is the best and the conditions where the service still needs improvement and then to make improvements in the specified aspects.

In an internet, QoS evaluates the ability of the network to deliver packets. The evaluation on QoS can be based on different aspects because the network provides various services. Generally speaking, QoS is the evaluation on the service ability to support the core requirements such as delay, jitter, and packet loss ratio in the packet delivery.

Traditional Packet Forwarding Service

In traditional IP networks, packets are treated equally. That is, the FIFO (first in first out) policy is adopted for packet processing. Network resources required for packet forwarding is determined by the order in which packets arrive. All the packets share the resources of the network. Network resources available to the packets completely depend on the time they arrive. This service policy is known as Best-effort, which delivers the packets to their destination with the best effort, with no assurance and guarantee for delivery delay, jitter, packet loss ratio, reliability, and so on.

The traditional Best-Effort service policy is only suitable for applications insensitive to bandwidth and delay, such as WWW, file transfer and E-mail.

New Applications and New Requirements

With the expansion of computer network, more and more networks become part of the Internet. The Internet gains rapid development in terms of scale, coverage and user quantities. More and more users use the Internet as a platform for their services and for data transmission.

Besides the traditional applications such as WWW, E-mail, and FTP, new services are developed on the Internet, such as tele-education, telemedicine, video telephone, videoconference and

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