Switch 7700 Configuration Guide

148 CHAPTER 7: QOS/ACL OPERATION
out (FIFO) policy. Switches and routers make their best effort to transmit the
packets to the destination, not making any commitment or guarantee of the
transmission reliability, delay, or to satisfy other performance requirements.
Ethernet technology is currently the most widely used network technology.
Ethernet has been the dominant technology of various independent Local Area
Networks (LANs), and many Ethernet LANs have been part of the Internet.
Moreover, along with the continuous development of the Ethernet technology,
Ethernet has become one of the major ways to access Internet users. To
implement the end-to-end QoS solution on the whole network, one must consider
the question of how to guarantee Ethernet QoS service. This requires the Ethernet
switching devices to apply Ethernet QoS technology and deliver the QoS
guarantee at different levels to different types of signal transmissions over the
networks, especially those having requirements of shorter time delay and lower
jitter.
Traffic Traffic refers to all packets passing through a switch.
Traffic Classification
Traffic classification means identifying the packets with certain characteristics,
using a matching rule called the classification rule that is set by the configuration
administrator, based on the actual requirements. The rule can be very simple. For
example, traffic with different priorities can be identified according to the ToS field
in the IP packet header.
There are also some complex rules. For example, the information over the
integrated link layer (Layer-2), network layer (Layer-3) and transport layer (Layer-4),
such as MAC address, IP protocol, source IP address, destination IP address, and
the port number of application can be used for traffic classification. Generally, the
classification standards are encapsulated in the header of the packets. The packet
content is seldom used as the classification standard.
Packet Filter
Packet filters filter network traffic. For example, the deny operation discards the
traffic that is matched with a traffic classification rule, while allowing other traffic
to pass through. With the complex traffic classification rules, Ethernet switches
enable the filtering of information carried in Layer 2 traffic to discard the useless,
unreliable or doubtful traffic, to enhance network security.
To fi lt er packe t s :
1 Classify the incoming traffic according to the classification rule.
2 Filter the classified traffic.
Traffic Policing
To deliver better service with limited network resources, QoS monitors the traffic
of the specific user on the incoming traffic, so it can make better use of the
assigned resource.