Traditional Packet Forwarding Service; New Requirements Brought Forth By New Services - H3C S3610-28P Operation Manual

Operation Manual – QoS
H3C S3610&S5510 Series Ethernet Switches
1.1 Introduction
Quality of Service (QoS) is a concept generally existing in occasions where service
supply-demand relations exist. QoS measures the ability to meet the service needs of
customers. Generally, the evaluation is not to give precise grading. The purpose of the
evaluation is to analyze the conditions where the services are good and the conditions
where the services still need to be improved, so that specific improvements can be
implemented.
In Internet, QoS measures the ability of the network to deliver packets. The evaluation
on QoS can be based on different aspects because the network provides diversified
services. Generally speaking, QoS is the evaluation on the service ability to support the
critical indexes such as delay, delay jitter and packet loss rate in packet delivery.

1.2 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.

1.3 New Requirements Brought forth by New Services

With the fast development of computer networks, more and more networks are
connected into Internet. Internet extends very quickly in scale, coverage and the
number of users. More and more users use the Internet as a platform for data
transmission and develop various applications on it.
Besides traditional applications such as WWW, FTP, and E-mail, Internet users also try
to develop new services on Internet, such as tele-education, tele-medicine, video
phones, video conferencing, and video on demand (VOD). Enterprise users also hope
to connect their branch offices in different locations through the VPN technology to
develop some transaction applications, such as to access to the database of the
company or to manage remote switches through Telnet.
Chapter 1 QoS Overview
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Chapter 1 QoS Overview