Differentiated services (DiffServ) is one technique for implementing Quality of Service (QoS)
policies. Using DiffServ in your network allows you to directly configure the relevant parameters
on the switches and routers rather than using a resource reservation protocol.This section
explains how to configure the M4100 and M7100 Managed Switch to identify which traffic class a
packet belongs to, and how it should be handled to provide the quality of service you want. As
implemented on the M4100 and M7100 Managed Switch, DiffServ allows you to control what
traffic is accepted and what traffic is discarded.

How you configure DiffServ support on a M4100 and M7100 Managed Switch varies depending
on the role of the switch in your network:

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Edge device. An edge device handles ingress traffic, flowing toward the core of the

network, and egress traffic, flowing away from the core. An edge device segregates
inbound traffic into a small set of traffic classes, and is responsible for determining a
packet’s classification. Classification is based primarily on the contents of the Layer 3
and Layer 4 headers, and is recorded in the Differentiated Services Code Point (DSCP)
added to a packet’s IP header.

•

Interior node. A switch in the core of the network is responsible for forwarding packets,

rather than for classifying them. It decodes the DSCP code point in an incoming packet,
and provides buffering and forwarding services using the appropriate queue
management algorithms.

Before configuring DiffServ on a particular M4100 and M7100 Managed Switch, you must
determine the QoS requirements for the network as a whole. The requirements are expressed in
terms of rules, which are used to classify inbound traffic on a particular interface. The switch
software does not support DiffServ in the outbound direction.

Rules are defined in terms of classes, policies, and services: