ASYNC_NETWORK_IO Waits SQL Server 2005 2008 2012 2014 2016
ASYNC_NETWORK_IO Wait type in SQL 2005 2008 2012 2014 or 2016 are associated with either a Network Performance issues in the Environment or a the client application is not processing results quickly enough from SQL Server.
As always, if you are One of the DBA’s who check Top Waits Stats on SQL Servers to get a insight on what is SQL Server waiting on actually for this performance issues. Below few tips on troubleshooting ASYNC_NETWORK_IO Waits SQL Server
The First thing when dealing with ASYNC_NETWORK_IO Wait types is check for Network issues in the environment, try looking at your NIC configuration on the server and make sure there are no issues with physical card.
For Troubleshooting ASYNC_NETWORK_IO Wait types in SQL Server, try to identify large result sets and verify with the application team/ developers team as to how results are being consumed.
When this wait ASYNC_NETWORK_IO happens to relate to application querying large results sets but not processing more than a few rows at a time which means application is not acknowledging of the large result is received and keeps SQL Server waiting.