 Rate limiting can be induced by the network protocol stack of the sender due to a received ECN-marked packet and also by the network scheduler of any router along the way.While a hardware appliance can limit the rate for a given range of IP-addresses on layer 4, it risks blocking a network with many users which are masked by NAT with a single IP address of an ISP.Deep packet inspection can be used to filter on the session layer but will effectively disarm encryption protocols like TLS and SSL between the appliance and the web server.