User Manual

8-Port or 16-Port Gigabit Smart Managed Pro Switch Model GS418TPP, GS510TLP, and GS510TPP
Configuration Examples User Manual455
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 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 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 (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.
Y
ou define these service levels by
configuring BA classes for each.
Creating policies
Use DiffServ policies to associate a collection of classes that you configure with one or more
QoS policy statements. The result of this association is referred to as a policy.
From a DiffServ perspective, two types of policies exist:
• Traffic Conditioning Policy. A policy applied to a Dif
fServ traffic class
• Service Provisioning Policy. A policy applied to a Dif
fServ service level
You must manually configure the various statements and rules used in the traffic conditioning
and service provisioning policies to achieve the desired T
raffic Conditioning Specification
(TCS) and the Service Level Specification (SLS) operation, respectively.
Traffic conditioning policy
Traffic conditioning pertains to actions performed on incoming traffic. Several distinct QoS
actions are associated with traffic conditioning:
• Dropping. Drop a packet upon arrival. This is useful for emulating access control list
operation using DiffServ, especially when DiffServ and ACL cannot coexist on the same
interface.
• Marking IP DSCP or IP Precedence. Marking/re-marking the DiffServ code point in a
packet with the DSCP value representing the service level associated with a particular
Dif
fServ traffic class. Alternatively, the IP precedence value of the packet can be
marked/re-marked.
• Marking CoS (802.1p). Sets the 3-bit priority field in the first/only 802.1p header to a
specified value when packets are transmitted for the traf
fic class.
An 802.1p header is
inserted if it does not already exist. This is useful for assigning a Layer 2 priority level