Protocol overhead in computer networking refers to the information that must be sent with data being routed through the network toward a destination. The information is stored at the start of the packet and is called a header. Depending on the exact network protocol being used, there can be a wide variety of information in the header, but most importantly are the destination address and the originating address. Even if a protocol between two applications uses little or no protocol overhead, the information will be wrapped in a network protocol with overhead to be sent through routers to reach the correct destination.
Network data packets are one of the basic network communication concepts that make possible the transmission of data across the Internet and other networks. A packet contains the actual data that is being transmitted, along with any information that the receiving application or device requires to understand what the packet is. When being routed between two points through the Internet, a packet might be wrapped inside another packet with a network protocol that helps to steer the information through several nodes to reach the target location. This wrapper packet will contain specific information that is not pertinent to the data being sent and is considered protocol overhead.
One widely used network protocol is called the transmission control protocol and Internet protocol (TCP/IP). Packets that are sent using TCP/IP have some protocol overhead, somewhere in the range of 40 to 80 bytes per packet. TCP/IP also has a programmed behavior that actually creates even more overhead, however. When a TCP/IP packet is delivered to a destination within a network, it sends a confirmation back to the sender of the delivered packet. This confirmation often has no data inside and is considered to be 100 percent protocol overhead.
An area in which protocol overhead can be of particular concern is when using wireless Internet, or Wi-Fi®. The signals transmitted from a wireless router to a computer travel through the air and can be intercepted, so the wireless protocol has a very large header that is attached to every packet sent. Many packets can be transmitted to a computer every second, and each packet contains the complete header. The size of the protocol overhead for a Wi-Fi® packet stems from the requirements of security, authorization and packet order. This causes the bandwidth that is available for the actual data to be lower with a Wi-Fi® protocol than with a machine that is hardwired to the Internet.