Cisco WS-X4604-GWY - VoIP Gateway Especificaciones descargar pdf (Pagina 66)

Chapter 2 Campus Infrastructure Considerations

Quality of Service

2-32

Cisco IP Telephony Network Design Guide

78-11103-03

Note All the values for WRED, WRR, and queue size are configurable.

Cisco Catalyst 6000 family switches also support the notion of trusted and

untrusted QoS on a per-port basis. This parameter is configured with the following

command:

set port qos mod/ports.. trust {untrusted | trust-cos | trust-ipprec |

trust-dscp}

This command allows you to configure the trust state as well as specify to trust

CoS or ToS (trust-ipprec) or DSCP (trust-dscp), which is an emerging Layer 3

standard under the Differentiated Services working group of the Internet

Engineering Task Force (IETF).

So far, this discussion has centered around the case depicted in Figure 2-14, where

voice traffic comes in as CoS 5 and PC traffic is zeroed out if there is any tag.

There may be times, however, when it is desirable to trust the PC CoS (if sending

tagged packets) or assign a value other than zero. This can be achieved on Catalyst

switches as well.

Figure 2-15 shows the case where the PC is trusted completely, and whatever CoS

it presents is honored.

Figure 2-15 PC Is Trusted

Example: set port qos 2/1 trust-ext trust-cos

CoS = 5

Trusted

CoS = 7 CoS = 7

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Cisco WS-X4604-GWY - VoIP Gateway Especificaciones Pagina 66