IFWXSlowDataFilter interface

Applies to: desktop apps only

The IFWXSlowDataFilter interface provides a method that the Firewall service can call to verify that the instance of the data filter object associated with a connection has completed the processing of all data for the connection before terminating it.

When to implement

An application filter may implement this interface to prevent data loss that results from the premature termination of connections.


The IFWXSlowDataFilter interface inherits from the IUnknown interface. IFWXSlowDataFilter also has these types of members:

  • Methods


The IFWXSlowDataFilter interface has these methods.

Method Description

Verifies that all data for this connection has been processed.



When an application running on a Forefront TMG Client or Firewall Client computer calls the Winsock WSACleanup function, the client DLL will close the Microsoft Firewall service session. As a result, the Firewall service will terminate all the connections that were created in this session.

Occasionally, this may lead to data loss, if the client application relies on TCP/IP for receipt acknowledgement. The connection could be closed after acknowledgement of a packet receipt because the slow connection delays the receipt of the remainder of the packets. This is not an issue if the client application uses application level acknowledgement.

To prevent data loss in these cases, an application filter should implement the IFWXSlowDataFilter interface.


Minimum supported client

None supported

Minimum supported server

Windows Server 2008 R2, Windows Server 2008 with SP2 (64-bit only)


Forefront Threat Management Gateway (TMG) 2010



See also

Filter Interfaces



Build date: 7/12/2010