The switch is QFX 5200.
The reason I am asking here is Tech support told my co-worker to add these lines to resolve some packet loss on one port. Based on my co-worker, the drop was gone after these lines added. I tried to figure out what theory behind this.
Juniper tech support asked to add the three lines:
set class-of-service shared-buffer egress percent 100
set class-of-service forwarding-classes class best-effort queue-num 0
set class-of-service forwarding-classes class best-effort no-loss
The second line is default configuration
I am trying to figure out what the first line does. Based on the Juniper docs, it is also the default configuration
I will dig the third line.
I am suspicious the drop disappeared because of something else.
thanks so much !!
Original Message:
Sent: 02-09-2021 11:11
From: Unknown User
Subject: CoS assistance needed
Hi!
Is this for EX4200 or another product? In EX4200, the "shared-buffer egress percent 100" tells the switch to allocate only the minimum amount of buffer memory to each interface. The rest is allocated to a shared buffer pool. This is normally what you want if you have lots of interfaces that each have lots of end-points connected to them, like in a distribution switch. In such scenarios you will have temporary buffer needs on various interfaces and the interfaces will be able to "borrow" memory from the shared buffer memory pool.
The second command seems odd, but it's important to have loss-priority low even on the best-effort class, at least on the EX4200.
If you post the switch type, someone can surely help you. If it's the EX4200, I can share a config that works really well in a distribution scenario.
/Fredrik
Original Message:
Sent: 02-09-2021 00:28
From: Unknown User
Subject: CoS assistance needed
Juniper Tech support told us to configure the following two lines:
set class-of-service shared-buffer egress percent 100
set class-of-service forwarding-classes class best-effort no-loss
Anyone tells me what these two lines exactly do ? What are pros and cons for these two lines ?
thanks a lot !!