Software-defined networks (SDNs) are made up of virtual network devices and services. Just like [[Cloud Computing|CSP]] provide virtual computers, many SDNs also provide virtual switches, routers, firewalls, and more. Most modern network hardware devices also support network virtualisation and software-defined networking. This means that physical switches and routers use software to perform packet routing. In the case of cloud networking, the SDN tools are hosted on servers located at the CSP’s data centre.