Netgear GS752TXS Technical Information download pdf (Page 300)

300 | Appendix B: Configuration Examples

GS752TXS Smart Switch Software Administration Manual

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.

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, there are two types of policies:

• 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. There are several

distinct QoS actions 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 co-exist 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 three-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 (i.e., DSCP or IP Precedence value) definition to

convey some QoS characteristics to downstream switches which do not routinely look at

the DSCP value in the IP header.

• Policing: a method of constraining incoming traffic associated with a particular class so

that it conforms to the terms of the TCS. Special treatment can be applied to out-of-profile

packets that are either in excess of the conformance specification or are non-conformant.

The DiffServ feature supports the following types of traffic policing treatments (actions):

• drop: the packet is dropped

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Netgear GS752TXS Technical Information Page 300