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prague
Beginner

Rate limit subscriber ASR9k BNG

Hi everyone ,

 

I use the policy map below to limit the subscriber, but when I try to use the whole package or when the speed test is at full load on router, I see packet losses. Anyone know the reason?

 

policy-map 20M
class class-default
police rate 20 mbps burst 3840000 bytes peak-rate 20 mbps peak-burst 7680000 bytes
conform-action transmit
exceed-action drop
!
!
end-policy-map

loss.PNG

 

 

Thanks

18 REPLIES 18

Working with shape. However, when the traffic is 20, the delays (ms) increases, probably due to the shape structure.

On ingress, PPPoE control frames (Ethertype 0x8863) are prioritised, but PPPoE keepalives (Ethertype 0x8864) are not. If the CPE is continuously exceeding the ingress policer rate, it's possible that keepalives will be dropped.

 

We're not rate limit pppoe right now. We are only limiting the interface as in the configuration I just wrote.. There is no such problem in our TR card type, on the same ASR9K in our tests.

I think this issue is related to our A9K-MOD400-SE card. Could the limiting structure be different?

When you have an ingress policer applied to the subscriber interface and there's congestion, policer will start dropping. PPPoE keepalive packets are not getting preferential treatment, so they may be dropped as well. If 3 consecutive PPPoE keepalives happen to be dropped, subscriber session will flap.

 

The question is how realistic is this in real life scenario. By far the most traffic that subscribers originate is TCP. TCP window mechanism will never allow the subscriber to continuously generate high traffic rate, so the ingress policer may only instantaneously become oversubscribed. In that scenario it's highly unlikely that three consecutive PPPoE keepalives are dropped by the policer.

 

Btw, the config snapshot that you have shared from TenGigE0/0/0/0 is not likely to be from a BNG solution. Can you share the "sh subscriber running-config ..." and "sh policy-map interface"?