RCSP Study Guide - QoS Class Priorities

There are five QoS priorities for Steelhead appliances. You assign a class priority when you create a QoS class. Once you have created a QoS class, you can modify its class priority. In descending order, class priorities are:

• Realtime

• Interactive

• Business Critical

• Normal Priority

• Low Priority

Enforcing QoS for Active/Passive FTP

Active/Passive FTP Operation

To configure optimization policies for the FTP data channel, define an in-path rule with the destination port 20 and set its optimization policy. Setting QoS for destination port 20 on the client-side Steelhead appliance affects passive FTP, while setting the QoS for destination port 20 on the server-side Steelhead appliance affects active FTP.

In the case of an active FTP session, data connections originate on a server sourced on port 20 and destined to a random port specified by the client. As such, specifying a QoS rule on the server-side Steelhead with a destination port of 20 is appropriate. With passive FTP however, data connections initiate on the client from a random port, and are destined to a server on a random port; as such, there is no seemingly simple way to apply a QoS rule based on the Layer 4 port information.

To help solve this problem, the Steelhead allows you to define a client-side QoS rule with a destination port of 20 to tell it that you would like to apply this QoS rule to a passive FTP data connection. The Steelhead will intelligently identify the actual ports used for the passive FTP data transfer, and apply the QoS logic set forth by the class where the rule has been applied.