Quanta Cloud Technology QuantaMesh QNOS5, Configuration Manual

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5.2.1. DiffServ Functionality and Switch Roles
How you configure DiffServ support in QNOS software varies depending on the role of the switch in your
network:

Edge device : An edge device handles ingress traffic, flowing towards 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 primarily based 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 in an incoming packet, and provides
buffering and forwarding services using the appropriate queue management algorithms.
Before configuring DiffServ on the 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 or outbound
traffic on a particular interface.
5.2.2. Elements of DiffServ Configuration
During configuration, you define DiffServ rules in terms of classes, policies, and services:

Class : A class consists of a set of rules that identify which packets belong to the class. Inbound
traffic is separated into traffic classes based on Layer 2, Layer 3, and Layer 4 header data. The
class type
All is supported; this specifies that every match criterion defined for the class must
be true for a match to occur.

Policy : A policy defines the QoS attributes for one or more traffic classes. An attribute
identifies the action taken when a packet matches a class rule. An example of an attribute is
to mark a packet. The switch supports the ability to assign traffic classes to output CoS
queues, and to mirror incoming packets in a traffic stream to a specific egress interface
(physical port or Port-channel).
QNOS software supports the Traffic Conditioning Policy type which is associated with an inbound traffic
class and specifies the actions to be performed on packets meeting the class rules:
– Marking the packet with a given DSCP, IP precedence, or CoS value. Traffic to be processed by the
DiffServ feature requires an IP header if the system uses IP Precedence or IP DSCP marking.
– Policing packets by dropping or re-marking those that exceed the class’s assigned data rate.
– Counting the traffic within the class.

Service: Assigns a policy to an interface for inbound traffic.
5.2.3. Configuration DiffServ to Provide Subnets Equal Access to External Network