Avaya QoS Manager 2.0 Guide de l'utilisateur télécharger pdf (Page 10)

Chapter 1

4 Avaya QoS Manager User Guide

DSCP

Differential Service Code Point (DSCP) provides a method of tagging IP

packets with priority information.

A DSCP value between 0 and 63 is added to the IP header of data

packets. Avaya QoS Manager supports 8 levels of forwarding priorities.

The 64 DSCP priority levels are mapped to the 8 levels in Avaya QoS

Manager. Each DSCP value is mapped to its corresponding priority level.

The DSCP Mapping table allows you to configure the correlation of

DSCP priorities to the priority levels in Avaya QoS Manager. DSCP

values 0-63 are assigned a priority level between 0 and 7.

Avaya QoS Manager allows you to assign DSCP priority values in the

DSCP Mapping table. For more information on using DSCP mapping,

refer to 

DSCP Mapping Table on page 27.

Class of Service

Class of Service (CoS) is the 802.1p priority scheme used to provide a

method of tagging packets with priority information.

A CoS value between 0-7 is added to the Layer II header of the data

packets. Zero is the lowest priority and seven is the highest.

Avaya QoS Managers priority scheme parallels that of CoS priority.

Avaya QoS Manager can use CoS tags to determine the priority with

which to forward packets.

Trust

A data packet can contain conflicting priority information. A DSCP tag

may give a packet a very high priority, while the CoS tag may give the

same packet a very low priority.

Trust determines the QoS scheme used by Avaya switches for packets

entering a module. There are four possible Trust settings:

 DSCP Value - Avaya switches use only the packet's DSCP tag. If

a packet entering a module matches no rules, or matches a rule

with a permit operation, the packet will be forwarded with a

priority based on the DSCP Mapping of the packet's DSCP tag.

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Avaya QoS Manager 2.0 Guide de l'utilisateur Page 10