Netgear XS728T – ProSAFE® 10 Gigabit Smart Managed Switch Guia Do Administrador

The DiffServ feature contains a number of conceptual QoS building blocks you can use to 
construct a differentiated service network. Use these same blocks in various ways to build 
other types of QoS architectures.

There are three key QoS building blocks needed to configure DiffServ:

Class

Policy

Service (that is, the assignment of a policy to a directional interface)

You can classify incoming packets at Layers 2, 3, and 4 by inspecting the following 
information for a packet:

Source and destination MAC addresses

EtherType

Class of Service (802.1 p priority) value (first or only VLAN tag)

VLAN ID range (first or only VLAN tag)

IP service type octet (also known as: ToS bits, precedence value, DSCP value)

Layer 4 protocol (such as TCP or UDP)

Layer 4 source and destination ports

Source and destination IP addresses

From a DiffServ point of view, there are two types of classes:

DiffServ traffic classes

DiffServ service levels or forwarding classes

With DiffServ, you define which traffic classes to track on an ingress interface. You can define 
simple BA classifiers (DSCP) and a wide variety of multifield (MF) classifiers:

Layer 2; Layers 3, 4 (IP only)

Protocol-based

Address-based

You can combine these classifiers with logical AND or OR operations to build complex 
MF-classifiers (by specifying a class type of all or any, respectively). That is, within a single 
class, multiple match criteria are grouped as an AND expression or a sequential OR 
expression, depending on the defined class type. Only classes of the same type can be 
nested; class nesting does not allow for the negation (that is, exclude option) of the 
referenced class.