27
Q
O
S C
ONFIGURATION
Introduction to QoS
QoS (Quality of Service) 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 when the service is the best and the conditions when the service still needs
improvement and then to make improvements in the specified aspects.
In 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, delay variation and packet loss ratio in the
packet delivery.
Traffic
Traffic means service traffic, that is, all the packets passing the switch.
Traffic Classification
Traffic classification means to identify packets conforming to certain characters
according to certain rules.
A classification rule is a filter rule configured to meet your management requirements.
It can be very simple. For example, you can use a classification rule to identify traffic
with different priorities according to the ToS field in the IP packet header. It can be
very complicated too. For example, you can use a classification rule to identify the
packets according to the combination of link layer (Layer 2), network layer (Layer 3)
and transport layer (Layer 4) information including MAC addresses, IP protocols,
source addresses, destination addresses, the port numbers of applications and so on.
Classification is generally based on the information in the packet header and rarely
based on the packet content.
Precedence
1
IP precedence, ToS precedence and DSCP precedence
Figure 64
DS fields and ToS bytes
The ToS field in an IP header contains 8 bits:
■
The first three bits indicate IP precedence in the range of 0 to 7.
■
Bit 3 to bit 6 indicate ToS precedence in the range of 0 to 15.
Summary of Contents for 4200G 12-Port
Page 10: ...8 CONTENTS...
Page 14: ...4 ABOUT THIS GUIDE...
Page 46: ...32 CHAPTER 5 LOGGING IN THROUGH WEB BASED NETWORK MANAGEMENT SYSTEM...
Page 48: ...34 CHAPTER 6 LOGGING IN THROUGH NMS...
Page 60: ...46 CHAPTER 9 VLAN CONFIGURATION...
Page 64: ...50 CHAPTER 10 MANAGEMENT VLAN CONFIGURATION...
Page 80: ...66 CHAPTER 13 GVRP CONFIGURATION...
Page 98: ...84 CHAPTER 15 LINK AGGREGATION CONFIGURATION...
Page 112: ...98 CHAPTER 18 MAC ADDRESS TABLE MANAGEMENT...
Page 126: ...112 CHAPTER 19 LOGGING IN THROUGH TELNET...
Page 162: ...148 CHAPTER 20 MSTP CONFIGURATION...
Page 274: ...260 CHAPTER 29 IGMP SNOOPING CONFIGURATION...
Page 276: ...262 CHAPTER 30 ROUTING PORT JOIN TO MULTICAST GROUP CONFIGURATION...
Page 298: ...284 CHAPTER 33 SNMP CONFIGURATION...
Page 304: ...290 CHAPTER 34 RMON CONFIGURATION...
Page 338: ...324 CHAPTER 36 SSH TERMINAL SERVICES...
Page 356: ...342 CHAPTER 38 FTP AND TFTP CONFIGURATION...
Page 365: ...Information Center Configuration Example 351 S4200G terminal logging...
Page 366: ...352 CHAPTER 39 INFORMATION CENTER...
Page 378: ...364 CHAPTER 40 BOOTROM AND HOST SOFTWARE LOADING...
Page 384: ...370 CHAPTER 41 Basic System Configuration and Debugging...
Page 388: ...374 CHAPTER 43 NETWORK CONNECTIVITY TEST...
Page 406: ...392 CHAPTER 45 CONFIGURATION OF NEWLY ADDED CLUSTER FUNCTIONS...