Efficient way to constraint parameters to cover all scenarios

To better explain my question simplifying the requirement. Have A Design which align the out of order packets which are coming on input ports and send out packets in incriminating order on output ports. But DUT can have multiple channel can active and no of packet can be up 1K. Does any one have suggestion for constraint to make sure it generates more realistic scenario and cover most of it.

For example:

DUT can support 8 Input channel Active at a time and packet can come in any order between 1 to 500. SO if Packet 50 first come then DUT will wait till all 1 to 49 packets will come so scenario needs to be generated such a way that all scenario can be covered.