Packet Lost in ping mpls ipv4/pseudowire

[Federico Torres]

Hi All, we have a pseudowire between two devices, one 7600 and one ASR900.

When we do a ping mpls pseudowire from 7600 to ASR9000, we don't have packet lost. But when the ping is from the ASR 9000 to 7600, we have some lost.

RP/0/RSP0/CPU0:x#ping mpls pseudowire 2XX.63.131.XX 157602 repeat 70 
Fri Jul 3 15:19:31.061 GMT
Sending 70, 100-byte MPLS Echos to 2XX.63.131.XX VC: 157602,
timeout is 2 seconds, send interval is 0 msec:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!
Success rate is 98 percent (69/70), round-trip min/avg/max = 2/2/3 ms

If we connect two devices into the pseudowire and do a Ping, We don't have any lost between the devices. The lost is only with the ping mpls pseudowire.

We did some test in our labs and saw the same behavior. Looks like a "design issue" or expected behavior and not an bad function of the network.

Can anybody help me with this doubt? 

Thanks!
Federico.

[Vinit Jain · Accepted solution]

Hello Federico

this is an expected behavior. This is happening due to Control-Plane Policing (CoPP). on ASR9k, there is no CoPP but there is LPTS which will rate-limit the packets hitting the CPU (LC or RP).

You will see ping packet drops as well if you perform multiple pings with size of interface MTU and df-bit set.

A good way to confirm that its expected or not, you can perform a test with 10000 pings and you will see a drop pattern. This will confirm the behavior.

Also, the packets from the device behind the PE is not getting dropped because they are being hardware switched.

Hope this clarifies

Regards

Vinit

PS: Please mark the question as answered if your query is clarified.

[Peerasan.T]

Hi Vinit,

I also face the similar issue but between NCS5500 and ASR920.
The loss of ping only occurred when ping from NCS5500 to ASR920, with a pattern as you said.

So, if this is an expected behavior. Is there any command to confirm that? like CPU's rate-limit 

[Federico Torres]

Thanks for your answer Vinit, was very helpful for me!

Regards.
Federico.