VoIP (Voice over IP) is where we transmit speech over an IP network. One of the big advantages of VoIP is that we only need one network, not an IP network and separate telephony network. Some of the challenges with VoIP is that data networks originally were not created for real-time traffic like telephony. QoS (Quality of Service) is often implemented to ensure that VoIP traffic is prioritized over other traffic on the network.