amazon-web-servicesamazon-ec2load-balancingnlbaws-nlb

Reset count metrics in AWS Network Load Balancer?


We have deployed Network Load Balancer target to nginx webserver using PHP-FPM.

We are receiving various reset count shown in below image. Could any one help understanding these counts?

CloudWatch metrics


Solution

  • These are TCP RST packet counts. For a TCP connection to remain alive, either party should exchange some data before idle timeout. On a UNIX OS (server/target), idle timeout is governed either by tcp_keepalive_time or tcp_keepidle parameter. On the client it depends upon how it's implemented or it may use the same parameters if it's also a UNIX OS. If either of the parties fail to send any data, the connection is closed after which if a client or a server send anything they'll receive a TCP packet with RST bit set and they'll know that the connection is no longer valid.