Qos Overview; Introduction; Traditional Packet Forwarding Service; New Requirements From Emerging Services - H3C LS-3100-52P-OVS-H3 Operation Manual

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QoS Overview

This chapter covers these topics:

Introduction

Traditional Packet Forwarding Service

New Requirements from Emerging Services

Congestion: Causes, Impacts, and Countermeasures
Major Traffic Management Techniques
Introduction
Quality of Service (QoS) is a concept concerning service demand and supply. It reflects the ability to
meet customer needs. Generally, QoS focuses on improving services under certain conditions rather
than grading services precisely.
In an internet, QoS evaluates the ability of the network to forward packets using different services. The
evaluation can be based on different criteria because the network may provide various services.
Generally, QoS refers to the ability to provide improved service by solving the core issues such as delay,
jitter, and packet loss ratio in the packet forwarding process.
Traditional Packet Forwarding Service
On traditional IP networks, devices treat all packets equally and handle them using the first in first out
(FIFO) policy. All packets share the resources of the network and devices. How many resources the
packets can obtain completely depends on the time they arrive. This service is called best-effort. It
delivers packets to their destinations as possibly as it can, without any guarantee for delay, jitter, packet
loss ratio, reliability and so on.
This service policy is only suitable for applications insensitive to bandwidth and delay, such as WWW,
file transfer and e-mail.
New Requirements from Emerging Services
The Internet has been growing along with the fast development of networking technologies. More and
more people use the Internet to transmit data, share video and do a lot of other things.
Besides traditional applications such as WWW, e-mail and FTP, network users are enjoying new
services such
Video-on-Demand (VoD). Enterprise users expect to connect their regional branches together with VPN
technologies to carry out operational applications, for instance, to access the database of the company
or to monitor remote devices through Telnet.
These new applications have one thing in common, that is, they all have special requirements for
bandwidth, delay, and jitter. For example, videoconference and VoD require high bandwidth, low delay
and jitter. As for mission-critical applications, such as transactions and Telnet, they may not require high
bandwidth but do require low delay and preferential service during congestion.
as tele-education, telemedicine, video telephone,
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videoconference and