QoS in sending or receiving direction

For controlling data transfer by means of QoS one can select whether the according rule applies to the sending or to the receiving direction. But which direction refers to sending and receiving for a given a data transfer depends on the particular point of view. The following two variants apply:

• The direction corresponds to the logical connection setup
• The direction corresponds to the physical data transfer over the appropriate interface

The differences are unveiled by looking at a FTP transfer. A client of the LAN is connected to the Internet through a LANCOM.

• During an active FTP session, the client sends by the PORT command the information to the server, on which port the DATA connection is expected. As the result, the server establishes the connection to the client and sends the data in the same direction. In this case, the logical connection as well as the real data stream over the interface go from the server to the client, and the LANCOM takes both as the receiving direction.
• Different is the case of a passive FTP session. Here the client itself establishes the connection to the server. The logical connection setup thus is from client to server, but the data transmission over the physical interface flows in the reverse direction from server to client.

With standard settings, a LANCOM assumes the sending or receiving direction depending on the logical connection setup. Because such a point of view may not be easy to follow in certain application scenarios, the point of view can alternatively be changed to the flow of the physical data stream.