Cisco Systems IE 2000 Classification Using Port Trust States

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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 38 Configuring Standard QoS
Information About Standard QoS
Classification Using Port Trust States
Trust State on Ports within the QoS Domain
Packets entering a QoS domain are classified at the edge of the QoS domain. When the packets are
classified at the edge, the switch port within the QoS domain can be configured to one of the trusted
states because there is no need to classify the packets at every switch within the QoS domain.
Figure 38-11 shows a sample network topology.
Figure 38-11 Port Trusted States within the QoS Domain
Configuring a Trusted Boundary to Ensure Port Security
In a typical network, you connect a Cisco IP phone to a sw itch port, as shown in Figure 38-11, and
cascade devices that generate data packets from the back of the telephone. The Cisco IP phone
guarantees the voice quality through a shared data link by marking the CoS level of the voice packets as
high priority (CoS = 5) and by marking the data packets as low priority (CoS = 0). Traffic sent from the
telephone to the switch is typically marked with a tag that uses the IEEE 802.1Q header. The header
contains the VLAN information and the class of service (CoS) 3-bit field, which is the priority of the
packet.
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Trunk
Trusted interface
Traffic classification
performed here
Trusted boundary
IP
P1P3