Transmission Control Protocol is a connection-oriented protocol and requires handshaking to set up end-to-end communications. It includes handshaking to negotiate authentication, encryption and maximum message size. Hardware handshaking is done with extra signals, often the RS-232 RTS/CTS or DTR/DSR signal circuits. They monitor TCP handshaking between packets to determine whether a requested session is legitimate. Handshaking is a technique of communication between two entities. Clashing type numbers would cause confusion when handshaking a connection and break cross-compatibility between implementations. Interface functions such as handshaking were offloaded to the 8049 firmware. In this mode, the ports can be used for simple I/O operations without handshaking signals. The simplest type of serial cable has no hardware handshaking. Third, PCI bus handshaking is simplified. This record should normally not be sent during normal handshaking or application exchanges. This extensive handshaking between the nodes made the networks slow. Even official photographs of visiting dignitaries were retouched to remove the image of their handshaking. This statement (as well as the degree sum formula) is known as the handshaking lemma. Various alternatives have been proposed for the tradition of handshaking.