请教qos相关的问题

[SwitchB] acl advanced 3001

[SwitchB-acl-ipv4-adv-3001] rule permit tcp destination-port eq 80

[SwitchB] traffic classifier http

[SwitchB-classifier-http] if-match acl 3001

[SwitchB] traffic behavior car_inbound

[SwitchB-behavior-car_inbound] car cir 204800

[SwitchB] qos policy car_inbound

[SwitchB-qospolicy-car_inbound] classifier http behavior car_inbound

[SwitchB-qospolicy-car_inbound] quit

[SwitchB] interface Ten-GigabitEthernet 1/0/1

[SwitchB-Ten-GigabitEthernet1/0/1] qos apply policy car_inbound inbound

qos的car 流量监管工作在网络层，请问如果在 Ten-GigabitEthernet1/0/1应用了qos 策略，是不是要求这个 Ten-GigabitEthernet1/0/1是三层口，qos 策略才能生效?

另外一个问题是如果给交换机的ip数据包 dscp 打了EF标签，数据包转发到下一个交换机，当这个交换机网络拥塞时，默认会不会优先转发数据包？