Netgear GS752TPS(B) - ProSAFE 48-Port Gigabit Stackable Smart Switch with PoE and 4 SFP uplinks Guia Do Programa

Class

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

Source/destination MAC address

EtherType

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

VLAN ID range (first/only VLAN tag)

Secondary 802.1p priority value (second/inner VLAN tag)

Secondary VLAN ID range (second/inner VLAN tag)

IP Service Type octet (also known as: ToS bits, Precedence value, DSCP value)

Layer 4 protocol (TCP, UDP etc.)

Layer 4 source/destination ports

Source/destination IP address

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

DiffServ traffic classes

DiffServ service levels/forwarding classes

DiffServ Traffic 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 multi-field (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 together 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 (i.e., exclude option) of the referenced 
class.

To configure DiffServ, you must define service levels, namely the forwarding classes/PHBs 
identified by a given DSCP value, on the egress interface. These service levels are defined 
by configuring BA classes for each.