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| 8.3 |  | Classification at the Access Layer |
| 8.3.1 |  | Classification at the access layer |

In order to be effective, QoS should be implemented end-to-end within a network. It is best to classify traffic as soon as possible and ideally at the network edge or access layer. Some network devices are able to signify the QoS requirements of their traffic directly while others will rely on access layer switches or border routers to perform this function on their behalf. Frames and packets can be marked as important by using Layer 2 Class of Service (CoS) settings in the User Priority bits of the 802.1p portion of the 802.1Q header or the IP Precedence/Differentiated Services Code Point (DSCP) bits in the Type of Service (ToS) Byte of the IPv4 header. The following sections outline the various classification techniques that can be applied at the ingress port of an access layer switch.