1.1 Introduction to Class-based QoS
Class-based QoS is used to classify packets sharing common features into one class and provide
the same QoS service for traffic of the same type by matching packets with certain rules. In this
manner, differentiated services are provided.
1.2 Class-based QoS Features Supported by the S3700HI
The S3700 supports simple traffic classification, complex traffic classification, and priority
mapping.
Simple Traffic Classification
On the S3700, you can perform simple traffic classification for packets based on the mappings
between packet priorities and Per-Hop Behaviors (PHBs) defined in a Differentiated Services
(DiffServ) domain. If packets come from an upstream device, the S3700 binds a DiffServ domain
to the inbound interface. In the DiffServ domain, the S3700 maps packet priorities to PHBs and
colors. On the S3700, congestion management is based on PHBs and congestion avoidance is
based on colors. If packets are sent to a downstream device, the S3700 binds a DiffServ domain
to the outbound interface. In the DiffServ domain, the S3700 maps PHBs and colors to priorities
so that the downstream device provides QoS services based on packet priorities.
Simple traffic classification is based on the following:
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DSCP priority of IP packets
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802.1p priority of packets in a VLAN
Complex Traffic Classification
Complex traffic classification is performed based on Layer 2 or Layer 3 information in packets
or by using access control lists (ACLs). You can bind a traffic classifier to a traffic behavior to
process packets matching the traffic classifier.
A traffic behavior is related to the current phase of packets and the current network load. For
example, when packets enter a node, the S3700 performs traffic policing and access control
based on the committed information rate (CIR). When packets leave a node, the S3700 shapes
the traffic and re-marks the priorities.
Complex traffic classification is based on the following:
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802.1p priority in VLAN packets
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VLAN ID in packets
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802.1p priority in CVLAN packets
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CVLAN ID in CVLAN packets
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Double tags of VLAN packets
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Inbound or outbound interface
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IP precedence in IP packets
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DSCP priority in IP packets
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SYN Flag field in Transmission Control Protocol (TCP) packets
S3700HI Ethernet Switches
Configuration Guide - QoS
1 Class-based QoS Configuration
Issue 01 (2012-03-15)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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