How many packets dropping rate is acceptable? Nexus Switch

[ciscomdsmagic]

We have seen packets dropping between NX3132 and the other device on one of 10GbE port, as shown below.

We don't see any obvious performance issue, or slowness.
The dropping rate is: 11325478 / 154134499786 = 0.007%

Is there anything wrong with packets dropping here, would 0.007% be acceptable and why?

# sh interface ethernet 1/3/1

TX
154134499786 unicast packets 6240518 multicast packets 559664 broadcast pa
ckets
154141299968 output packets 796781312922182 bytes
98230397218 jumbo packets
0 output error 0 collision 0 deferred 0 late collision
0 lost carrier 0 no carrier 0 babble 11325478 output discard
0 Tx pause

[luis_cordova]

Hi @ciscomdsmagic ,

Check this discussion of the community, about a similar doubt:

https://community.cisco.com/t5/switching/packet-drop-rate-percentage/td-p/1215438

I hope you find it useful.

Remember to mark the correct answers as solved, because that helps other users with similar doubts.

Regards

[Richard Burts]

There are several things that we should consider as we try to answer this question. One of those things would be the number/percentage of packets dropped. And 0.007 seems a pretty low percentage. But we also need to consider what kind of traffic this is and what might be the impact of dropped packets. If most of the traffic is TCP packets, then the acknowledgements and retransmissions of missing packets provided by TCP would say that these dropped packets are not a problem at all. But if the traffic is some other protocol then perhaps the dropped packets might be significant. Think of a possible scenario in which some UDP based protocol is sending a file with 1,000 packets and after transmission uses a checksum to validate the transmission. If 1 packet (out of 1,000) was dropped then the file transmitted is not valid and we have to start over again. In that case 0.007 might be pretty significant. So you really need to know your own environment to be able to answer the significance of 0.007 dropped packets.

HTH

Rick

[ciscomdsmagic]

Thanks Richard!

TCP here.

What would you say  to the people said packets dropping IS a bad thing, no matter what? I know they are overacted, but I don't know how to better explain.

By adding additional connections between additional ports on two sides would change anything?

[Joseph W. Doherty]

"What would you say to the people said packets dropping IS a bad thing, no matter what?"

That perhaps they should study the issue of congestion collapse, in the early days of networking.

Remember with TCP, if there's enough data, it will generally try to transfer data at the host interface's physical bandwidth, which often is more than available transit bandwidth. In such cases, drops are to be expected although some of the latest TCP variants try to detect transit congestion, and slow their transmission rate, before there's any packet drops.

You might want to research the subject "goodput".

"By adding additional connections between additional ports on two sides would change anything?"

Maybe, maybe not.

[Richard Burts · Accepted solution]

I want to respond to this

What would you say  to the people said packets dropping IS a bad thing, no matter what?

I would say that these people are idealists. And I would say that they certainly are not the ones who are responsible for paying the bills for the network. I am sure that all of us would really like to implement networks that have sufficient bandwidth and sufficient processing capability that no packet ever got dropped. But the financial reality is that very few of us can afford that.

I am not clear what you are asking about additional connections between additional ports. I assume that it is implying that there could be some load sharing. In some situations load sharing can certainly improve performance and perhaps reduce the number of drops. In other situations where something is sending traffic that is very bursty it could exceed the capacity of the interface causing drops. Load sharing would not be particularly effective about that type of issue.

HTH

Rick

[Richard Burts]

This has been an interesting discussion and I am glad that you have found it helpful. Thank you for marking this question as solved. This will help other participants in the community to identify discussions which have helpful information. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.

HTH

Rick