Network Load Balancer TCP Idle Timeout Configuration: Impact on Existing Connections

Question

I provide MQTT-based services through a Network Load Balancer, and I've been troubled by idle timeout issues. Now I've noticed there's a new attribute called `tcp.idle_timeout.seconds` that can be set on the listener.

Questions:
1. Will updating this setting apply to existing TCP connections?
2. Will updating this setting cause the connection to be interrupted?

Praveen Muppala · Accepted Answer

Hello Vincent,

Updating the tcp.idle_timeout.seconds setting on a Network Load Balancer (NLB) will only apply to new TCP connections, not to those already in progress. Therefore, modifying this setting will not interrupt or affect existing connections.

For more details, you can check the full AWS blog post - [Introducing NLB TCP configurable idle timeout](https://aws.amazon.com/blogs/networking-and-content-delivery/introducing-nlb-tcp-configurable-idle-timeout/)

Network Load Balancer TCP Idle Timeout Configuration: Impact on Existing Connections

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