title: HTTP2 PING frames over AWS ALB (gRPC keepalive ping)
body: <p>I'm using AWS Application Load Balancer (ALB) to expose the ASP.NET Core gRPC services. The services are running in Fargate containers and expose unsecured HTTP ports. ALB terminates the outer TLS connection and forwards the unencrypted traffic to a target group based on the route. The gRPC application has several client streaming endpoints and the client can pause the streaming for several minutes. I know that there are HTTP2 PING frames, which can be used in such cases, to keep alive the connection that has no data transmission for some amount of time.</p>
  <p>The gRPC server is configured to send HTTP2 pings every 20 seconds for keeping the connection alive. I tested this approach and it works, the ping frames went from the server and were acknowledged by the client.
  But this approach fails when it comes to ALB. During the transmission pauses, I don't see any packages from the server behind the load balancer (I use Wireshark). Then after the timeout of 1 minute, the ALB resets the connection.</p>
  <p>I tried to use client-sent HTTP2 pings as well. But the connection also resets in 1 minute and I have no evidence whether these ping packages actually reached the server behind the ALB.
  I have an assumption that AWS ALB doesn't allow such packets to pass over it, but I didn't find any documentation that proves it.</p>