Qos Overview; Typical Cos And Dscp Values For Voice And Video Networks - Cisco WS-C6506 Software Manual

QoS Overview

QoS Overview
These sections provide an overview of QoS:
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•
•

Typical CoS and DSCP Values for Voice and Video Networks

The IETF recommends that you use several values for the different traffic types that are found in voice
and video networks. Automatic QoS uses these values to configure such QoS parameters as
CoS-to-queue maps, differentiated services code point (DSCP)-to-CoS maps, and so on.
Catalyst 6500 series switches use the differentiated services (DIFFSERV) model for QoS. This model
outlines three traffic types:
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•
•
Four traffic classes exist within the AF class. The classes are denoted by AFXY where X is the class
number and Y is the drop precedence number. X corresponds to a queue, and Y corresponds to a drop
precedence value within the queue (either WRED or tail drop). EF has the highest priority, BE has the
lowest priority, and the priority for AF is somewhere in between.
See
types. The values listed are assumed when configuring the CoS-to-queue maps and other CoS/DSCP
value-dependent configurations with the automatic QoS macro.
Table 53-1
CoS Value
0
3
5
4
2
1
6
7
1. Some values differ from the current QoS default values for Catalyst software (such as CoS-to-DSCP maps).
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
53-2
Typical CoS and DSCP Values for Voice and Video Networks, page 53-2
QoS Scenario—Cisco IP Phone, page 53-3
QoS Scenario—Cisco SoftPhone, page 53-3
EF (Expedited Forwarding)
AF (Assured Forwarding)
BE (Best Effort)
Table 53-1 for the recommended CoS and DSCP values for the voice networks and other traffic
Typical CoS and DSCP values in Cisco Voice and Video Networks
1
DSCP
0
26 (IETF recommended)
46 (IETF recommended)
34 (IETF recommended)
18
10
48
Chapter 53
Significance
Default traffic (BE class)
Voice/video call control/signaling (TCP)
AF31 class
Voice-bearer stream (RTP/UDP)
EF class
Video-bearer stream
AF41 class
Mission critical/transactional traffic
AF21 class
Streaming video (not interactive)
AF11
Routing protocols (as default)
Spanning Tree Protocol
Using Automatic QoS
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