Allied Telesis AT-S63 - Manual (Page 285)

AT-S63 Management Software Menus Interface User’s Guide
Section II: Advanced Operations 285
is dictated by the QoS policy, as explained in Chapter 17, “Quality of
Service” on page 337.
In summary, a classifier is a list of variables that define a traffic flow. You
apply a classifier to an ACL or a QoS policy to define the traffic flow you
want the ACL or QoS policy to affect or control.
Classifier
Criteria
The components of a classifier are defined in the following subsections.
Destination MAC Address (Layer 2)
Source MAC Address (Layer 2)
You can identify a traffic flow by specifying the source and/or destination
MAC address. For instance, you might create a classifier for a traffic flow
destined to a particular destination node, or from a specific source node to
a specific destination node, all identified by their MAC addresses.
The management software does not support a classifier based on a range
of MAC addresses. Each source and destination MAC address must be
considered as a separate traffic flow, requiring its own classifier.
Ethernet 802.2 and Ethernet II Frame Types (Layer 2)
You can create a classifier that filters packets based on Ethernet frame
type and whether a packet is tagged or untagged within a frame type. (A
tagged Ethernet frame contains within it a field that specifies the ID
number of the VLAN to which the frame belongs. Untagged packets lack
this field.) Options are:
ˆ Ethernet II tagged packets
ˆ Ethernet II untagged packets
ˆ Ethernet 802.2 tagged packets
ˆ Ethernet 802.2 untagged packets
802.1p Priority Level (Layer 2)
A tagged Ethernet frame, as explained in “Tagged VLAN Overview” on
page 608, contains within it a field that specifies its VLAN membership.
Such frames also contain a user priority level used by the switch to
determine the Quality of Service to apply to the frame and which egress
queue on the egress port a packet should be stored in. The three bit binary
number represents eight priority levels, 0 to 7, with 0 the lowest priority
and 7 the highest. Figure 85 illustrates the location of the user priority field
within an Ethernet frame.