5G NR, Wi-Fi, and Bluetooth communications are all data based where the data (stream of bits, a bit being either a 1 or a 0) is sent in discrete packets, each packet being a sequence of bytes (each byte contains 8 bits). Packet data communication systems employ the so-called protocols. Here a protocol is a set of rules that must be followed for two devices to communicate with each other. Protocols are layered on top of each other to form a communication architecture referred to as a protocol stack. Each protocol provides a function or functions required to make data communication possible. Typically, many protocols are used so that overall functioning can be broken down into manageable pieces. 5G and Wi-Fi networks communicate via the Internet. The Internet communicates with the aid of a suite of software network protocols called Transmission Control Protocol/Internet Protocol (TCP/IP) or User Datagram Protocol/Internet Protocol (UPD/IP). TCP/IP and UDP/IP work together with a data link layer and a physical layer (these latter layers combined are referred to as the Network Access Layer) to create an effective packet switched network for Internet communications. In this chapter, a brief introduction to TCP, UDP, IP, data link, and physical layer protocols is presented.