H3C S5600 Series Operation Manual page 828

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Operation Manual – QoS-QoS Profile

H3C S5600 Series Ethernet Switches

The first three bits indicate IP precedence in the range 0 to 7.

Bit 3 to bit 6 indicate ToS precedence in the range of 0 to 15.

In RFC2474, the ToS field in IP packet header is also known as DS field. The first

six bits (bit 0 through bit 5) of the DS field indicate differentiated service codepoint

(DSCP) in the range of 0 to 63, and the last two bits (bit 6 and bit 7) are reserved.

Table 1-2 Description on IP Precedence

IP Precedence (decimal)

In a network providing differentiated services, traffics are grouped into the following four

classes, and packets are processed according to their DSCP values.

Expedited Forwarding (EF) class: In this class, packets can be forwarded

regardless of link share of other traffic. The class is suitable for preferential

services with low delay, low packet loss ratio, low jitter, and assured bandwidth

(such as virtual leased line);

Assured forwarding (AF) class: This class is further divided into four subclasses

(AF1/2/3/4) and a subclass is further divided into three drop priorities, so the AF

service level can be segmented. The QoS rank of the AF class is lower than that of

the EF class;

Class selector (CS) class: This class comes from the IP ToS field and includes

eight subclasses;

Best Effort (BE) class: This class is a special class without any assurance in the

CS class. The AF class can be degraded to the BE class if it exceeds the limit.

Current IP network traffic belongs to this class by default.

Table 1-3 Description on DSCP precedence values

DSCP value (decimal)

IP Precedence (binary)

DSCP value (binary)

Chapter 1 QoS Configuration

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