loadBalancerCapabilities If set to HttpLevel and the application pool is stopped, HTTP.sys will return an HTTP 503 error. ...

[loadBalancerCapabilities] If set to HttpLevel and the application pool is stopped, HTTP.sys will return an HTTP 503 error.  If set to TcpLevel, HTTP.sys will reset the connection.  This is useful if a load balancer recognizes one of the response types and subsequently redirects it.