Hi all !
I have an ASR 9001 router on which I have for the moment not configured QoS at all.
Here is the diagram of my lab network :
[HOST_A] ---- [ASR9001] ---- [ROUTER2] ---- [HOST_B]
I have configured a BGP peering session between ASR9001 and ROUTER2.
From HOST_A, I'm sending a huge traffic, largely exceeding the capacity of the (ASR9001--ROUTER2) link. I can see many packet drops on ASR9001 (outgoing towards ROUTER2).
But strangely the BGP session between ASR9001 and ROUTER2 remains UP at all times and I can see no BGP keepalive packet loss on ROUTER2 (incoming from ASR9001). I know that ASR9001 marks the BGP control packets that is sends out to the network with the DSCP field "CS6". But since there is no QoS policy configured on ASR9001, we are supposed to only have a single queue on the port of ASR9001 facing ROUTER2 and thus we should lose BGP packets on that port.
Do you know why BGP packets are transmitted correctly despite the saturation of the link ?
Thanks !