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Chapter 5
Configuring the Switch
33
48-Port 10/100 + 4-Port Gigabit Switch with WebView and Power over Ethernet
The Switch supports a common method of prioritizing
layer 3/4 traffic to meet application requirements. Traffic
priorities can be specified in the IP header of a frame
using the priority bits in the Type of Service (ToS) octet. If
priority bits are used, the ToS octet may contain six bits for
Differentiated Services Code Point (DSCP) service. When
these services are enabled, the priorities are mapped to
a Class of Service value by the Switch and the traffic then
sent to the corresponding output queue. Because different
priority information may be contained in the traffic, the
Switch maps priority values to the output queues in the
following manner:
The precedence for priority mapping is DSCP Priority and
then Default Port Priority.
To enable DSCP priority mapping, check the DSCP Priority
Status Enabled checkbox.
Priority Status Enables the DSCP priority mapping.
(Enabled is the default setting.)
DSCP to CoS Maps Differentiated Services Code Point
values to CoS values.
Click Save Settings to save the changes.
QoS > DiffServ Settings
QoS > DiffServ Settings
The commands described in this section are used to
configure Quality of Service (QoS) classification criteria
and service policies. Differentiated Services (DiffServ)
provides policy-based management mechanisms used for
prioritizing network resources to meet the requirements
of specific traffic types on a per hop basis. Each packet is
classified upon entry into the network based on access
lists, IP Precedence, DSCP values, or VLAN lists. Using
access lists allows you to select traffic based on Layer 2,
Layer 3, or Layer 4 information contained in each packet.
Based on configured network policies, different types of
traffic can be marked for different types of forwarding.
All switches or routers that access the Internet rely on class
information to provide the same forwarding treatment
to packets in the same class. Class information can be
assigned by end hosts, or switches or routers along the
path. Priority can then be assigned based on a general
policy, or a detailed examination of the packet. However,
note that detailed examination of packets should take
place close to the network edge so that core switches
and routers are not overloaded. Switches and routers
along the path can use class information to prioritize the
resources allocated to different traffic classes. The manner
in which an individual device handles traffic in the DiffServ
architecture is called per-hop behavior. All devices along
a path should be configured in a consistent manner to
construct a consistent end-to-end QoS solution.
Class Map
A class map is used for matching packets to a specified
class. The class map uses the Access Control List filtering
engine, so you must also set an ACL to enable filtering for
the criteria specified in the class map.
The class map is used with a policy map to create a
service policy for a specific interface that defines packet
classification, service tagging, and bandwidth policing.
NOTE: One or more class maps can be assigned
to a policy map.
Class Name Name of the class map. (Range: 1-32
characters)
Type Only one match command is permitted per class
map, so the match-any field refers to the criteria specified
by the lone match command.
Description A brief description of a class map. (Range: 1-
256 characters)
Add Creates a new class map using the entered class
name and description.
Remove Removes the selected class from the list.
Edit Class Element Modifies the class map criteria used
to classify ingress traffic.