Users Guide

Dell(conf-class-map)#match ip vlan 5
4 Create a QoS input policy.
CONFIGURATION mode
Dell(conf)#qos-policy-input pp_qospolicy
5 Configure the DSCP value to be set on matched packets.
QOS-POLICY-IN mode
Dell(conf-qos-policy-in)#set ip-dscp 5
6 Create an input policy map.
CONFIGURATION mode
Dell(conf)#policy-map-input pp_policmap
7 Create a service queue to associate the class map and QoS policy map.
POLICY-MAP mode
Dell(conf-policy-map-in)#service-queue 0 class-map pp_classmap qos-policy pp_qospolicy
Classifying Incoming Packets Using ECN and
Color-Marking
Explicit Congestion Notification (ECN) is a capability that enhances WRED by marking the packets instead of causing WRED to
drop them when the threshold value is exceeded. If you configure ECN for WRED, devices employ this functionality of ECN to
mark the packets and reduce the rate of sending packets in a congested, heavily-loaded network.
ECN is a mechanism using which network switches indicate congestion to end hosts for initiating appropriate action. End hosts
uses two least significant bits of ToS to indicate that it is ECT. When intermediate network node encounters congestion,
remarks ECT to CE for end host to take appropriate action. During congestion, ECN enabled packets are not subject to any
kind of drops like WRED except tail drops. Though ECN & WRED are independent technologies, BRCM has made WRED a
mandatory for ECN to work.
On ECN deployment, the non-ECN packets that are transmitted on the ECN-WRED enabled interface will be considered as
Green packets and will be subject to the early WRED drops. Typically the TCP-acks, OAM, ICMP ping packets will be non-ECN
in nature and it is not desirable for this packets getting WRED dropped.
In such a condition, it is necessary that the switch is capable to take differentiated actions for ECN/Non-ECN packets. After
classifying packets to ECN/Non-ECN, marking ECN and Non-ECN packets to different color packets is performed.
Policy based ingress QOS involves the following three steps to achieve QOS:
1. Classification of incoming traffic.
2. Specify the differentiated actions for different traffic class.
3. Attach the policy-map to the interface.
Dell Networking OS support different types of match qualifiers to classify the incoming traffic.
Match qualifiers can be directly configured in the class-map command or it can be specified through one or more ACL which
in turn specifies the combination of match qualifiers.
Until Release 9.3(0.0), support is available for classifying traffic based on the 6-bit DSCP field of the IPv4 packet.
As a part of this feature, the 2-bit ECN field of the IPv4 packet will also be available to be configured as one of the match
qualifier. This way the entire 8-bit ToS field of the IPv4 header shall be used to classify traffic.
The Dell Networking OS Release 9.3(0.0) supports the following QOS actions in the ingress policy based QOS:
1. Rate Policing
Quality of Service (QoS) 648