When a new flow is created, a subscriber flow policy is assigned to it, which specifies how to treat all the flows within that subscriber. The actions that can be defined in a subscriber flow policy are:

• TCP Optimization. Improves TCP traffic performance. It specifies whether to apply optimization to TCP traffic. It is recommended to enable it (the default value).
• Maximum speed limit (shaping). It limits the speed to a given value. It is possible to limit in the downlink and/or uplink direction. The limit applies to all flows matching the policy belonging to the same subscriber. For example, if all video streaming flows are assigned to a flow policy with a 6 Mbps limit, and the subscriber has three video streaming flows at the same time, the three flows will share the 6 Mbps limit (getting around 2 Mbps each). It is possible to define bursts that allow flows to exceed temporally the limit (see the end of this section).
• ‍Block.  It blocks all flows falling in the blocking policy, in both directions, and does not let it proceed. It should be used with care, to avoid affecting traffic different to the one intended.
• Skip subscriber rate limitation. The traffic from flows getting this policy will no longer be affected by the rate limitation specified in the rate policy for this subscriber. They will only get the rate limitation specified by this flow policy (if any).  

These policies are configured in the menu option Configuration->Subscriber Flows, selecting the tab POLICIES.

Burst Options

Regarding bursts, they are configured under Burst Options of the appropriate direction. Burst policy is defined by four parameters:

• Burst Rate: it is the maximum rate during the burst, typically bigger than the normal shaping max rate (e.g., allow burst of 20 Mbps for flows normally limited to 10Mbps).
• ‍Burst Duration: it is the duration of the burst, for how long the burst rate can be sustained.
• ‍Burst Threshold: it is an average speed that, if exceeded, prevent a new burst from happening. It is the way to control when a new burst can be granted. For example, for a 10Mbps limit with 20Mbps bursts, a 5Mbpsburst threshold will require the subscriber flows to drop the speed to half its normal limit before allowing a new burst.
• ‍Burst Threshold Window: it is the period, in seconds, used to compute the average speed that is checked versus the threshold. The longer the window, the bigger the weight of past subscriber activity on the decision of grating a new burst.

Blocking incoming Traffic

It is possible to block incoming traffic, initiated from the Internet (TCP connections, UDP flows or other IP traffic like ICMP pings). Todo so, there are Drop Incoming Connections section as part of a Subscriber Flow policy.