Traffic Filtering and Marking is a vSphere Distributed Switch feature that protects virtualized systems from unwanted traffic and allows to apply QoS tags to certain type of traffic.
Distributed Switch requires Sphere Enterprise Plus license. But if you have vSAN, vDS is included in vSAN license so it will work on vSphere Standard license as well.
This tool is also great for a remote POC or your home lab. It will help you to invoke a controlled vSAN host partition or isolation and learn the behavior of HA or vSAN cluster. Or verify if HA your configuration is correct. This is a great tool especially for testing vSAN stretched cluster behaviour.
Sometimes creating a full site partition requires to involve a networking team, that may not be available on demand. This tool can help a virtualization team to test various scenarios on their own.
In the example below I used two DROP rules to discard the traffic coming to esx12 and esx13 in my 4-host cluster.
This way I created three cluster partitions: esx12, esx13 and the rest of the cluster (esx10 and esx11).
Right after I disabled the rules, cluster got back to normal.