- 在DC里面，特别是Storage Network/FCOE，对pkt drop很敏感，常用的是2种QOS
- ECN
- PFC
- PFC - Prority Flow Control.
- ECN - Explicit Congestion Notification,
- 是DSCP后面的2 bit.
- 00 - Not supported
- 01/10 - Supported
- 11 - CE : congestion encountered
- 如何Work:
- Server pkt 通过 Router
- Router发现有Egress congestion, 或者定义的min/max threshold, 开始set ECN to CE
- Client收到CE pkt后，通过TCP adjust window to slow down traffic.
- 一般是定义在Egress interface，config在后面
interface et3/1/1
mtu 9000
speed force 40gfull
no switchport
ip address 10.1.1.1/24
qos trust dscp
tx-queue 0
random-detect ecn minimum-threshold xxxx bytes max yyyy bytes
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