Symptoms
When you use Microsoft SQL Server 2012 with the Service Broker, database mirroring or Availability Groups, the connection to SQL Server database has high latency and the response takes much more time.
Cause
The issue occurs because, when the communication between two servers that use Service Broker, database mirroring or Availability Groups occurs, the window size of TCP protocol does not expand automatically. TCP window size determines the number of bytes that a sender can transmit without receiving an acknowledgement. When the client is receiving data from SQL Server database, the client holds a constant TCP window size. After large amount of data is sent from SQL Server database, the window size on the client will gradually come down to 0. Therefore, the connection to SQL Server database makes high latency and the response takes much more time.
Resolution
The issue was first fixed in the following cumulative update of SQL Server.
Cumulative Update 1 for SQL Server 2012 SP2 /en-us/help/2976982
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
