User Manual

S350 Series 24-Port (PoE+) and 48-Port Gigabit Ethernet Smart Switches
Configuration Examples User Manual344
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 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, 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 DSCP value, on the egress interface. You 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 DiffServ traffic class
• Service Provisioning Policy. A policy applied to a DiffServ service level
You must manually configure the various statements and rules used in the traffic conditioning
and service provisioning policies to achieve the desired Traffic 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
DiffServ 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 traffic class. An 802.1p header is
inserted if it does not already exist. This is useful for assigning a Layer 2 priority level
based on a DiffServ forwarding class (such as the DSCP or IP precedence value)