Huawei v200r001 Chapter 1 QoS Overview

User Manual - Configuration Guide (Volume 3)

Versatile Routing Platform Chapter 1

QoS overview

1-1

Chapter 1 QoS Overview

In traditional IP networks, all packets are processed equally. Each router processes the

packets with first-in first-out (FIFO) policy. It sends the packet to the destination in the

mode of best-effort, but the throughput, delay, delay jitter and packet discarding rate

cannot be predicted. The situation can be very perfect, or be very bad, and it can on l y

be determined by the state of the network. However, people raise higher demand for

the network along with the rapid development of computer networ k. As more and more

voice, image and important data are transmitted over the network, which are s ens itiv e

to bandwidth, delay, jitter and real-time features, network resources now become

increasingly diversified. At the same time, the service quality also becomes an

important issue. People expect that they can get enough guarantee in the aspects of

the throughput, delay, delay jitter and discarding rate of packets, so that their special

requirements on the special services can be satisfied. People also expect t hat they

could obtain customized service quality according to the c lient types. One way to solve

this problem is to increase the bandwidth. But bandwidth increase is limited and costs a

lot. The problem can only be solved to a certain extent.

QoS (Quality of Service) indicates the integration of a series of technologies that per mit

users to get predictable service quality in the aspects of throughput, delay j itter, delay,

and packet discarding rate. QoS (Quality of Service) provides network service function

with different service quality according to different demands. It can be sa id that the

capability of providing QoS is the basic requirement for future IP ne tworks.

Usually, the service of QoS is classified into the following three types:

Best-effort Service indicates to work with “the best effort”, but it cannot guarante e the

service quality.

This service type uses signaling mechanism to inform the data flow pas sing route to

obligate resource, so it can implement quality guarantee very well. Bur when the size of

the network is large, the cost is high, and then the integrat ed service is usually

applicable for the edge of network. The signaling used to transfer QoS req uest is RSVP

(Resource ReSerVation Protocol), which informs the QoS request of application to the

router.

The integrated service provides the following two types of services:

1) Guarantee: i.e., to provide guaranteed bandwidth and delay limit to satis fy the

application request

2) Load control: to guarantee that it would provides the packets services alm ost the

same as those when the network is not overloaded even if the network is