This is a 3-3-1 defense, but NOT a cup.  It seeks to clog the middle of the field by having one mark on each handler, forcing middle.  The middle handler mark ("Clamidia") always seeks to prevent continuation in the same direction that the disc was swung.  All handler marks Poach out into the forced lane when their charge does not have the disc, but must still be able to recover and do their primary job when the disc is swung.

The second three are always forcing a cutter Out, essentially playing Person defense unless called off by the deep, or unless the cutter becomes a handler.  Note that they may need to switch the side they are marking if a handler mark is broken.

Finally, recognize that this works even better when the offense starts in Vertical stack instead of Horizontal.  Everyone's job is still the same, but Clamidia's job is much easier as there is no need to recover without a middle handler: