H3C S7500 Series Ethernet Switches Operation Manual

Operation Manual – QoS
H3C S7500 Series Ethernet Switches Chapter 1
QoS Configuration
1-3
The precedence values of an IP packet represent 8 different service classes.
Table 1-1 Description on IP Precedence
IP Precedence (decimal) IP Precedence (binary) Description
0 000 routine
1 001 priority
2 010 immediate
3 011 flash
4 100 flash-override
5 101 critical
6 110 internet
7 111 network
The Diff-Serv network defines four traffic classes:
z Expedited Forwarding (EF) class: In this class, packets can be forwarded
regardless of link sharing of the other traffic. The class is suitable for preferential
services with low delay, low packet loss ratio, low jitter and guaranteed bandwidth
(such as virtual leased line);
z Assured forwarding (AF) class: This class is further divided into four sub-classes
(AF1/2/3/4) and a sub-class is further divided into three drop priorities, so the AF
service level can be segmented. The QoS rank of the AF class traffic is lower than
that of the EF class traffic;
z Class selector (CS) class: This class comes from the IP TOS field and includes 8
classes;
z Best Effort (BE) class: This class is a special class without any assurance in the
CS class. The AF class traffic can be degraded to the BE class traffic if it exceeds
the limit. Current IP network traffic is of the BE class by default.
Table 1-2 Description on DSCP precedence
Keyword
DSCP precedence
(decimal)
DSCP precedence
(binary)
ef 46 101110
af11 10 001010
af12 12 001100
af13 14 001110
af21 18 010010
af22 20 010100