We encountered an issue where we upload customer files to AWS S3. On one occasion, the upload failed. During troubleshooting, we found that it might be due to a small MTU configuration in the network path, because running sudo ping -D -s 1000 xxxxx.com to the server returned an error. However, as far as I know, when the MTU suddenly becomes smaller, a type=3, code=4 ICMP message PTB (Packet Too Big) should be received, and TCP/IP should adjust the size and still upload successfully. Some people suggest that the issue is caused by the load balancer dropping the ICMP messages, but this doesn’t seem quite right. I would like to ask what the possible reasons might be. Thank you.