function management header. The optional control information present in the leading request units (RUs) of an RU chain that allows one half-session in an LU-LU session to perform such functions as: (1) carry a request that a conversation be established between two transaction programs; (2) carry information that relates to an error on the session or conversation; (3) carry LU-LU password verification data; (4) select a destination as the session partner and control the way the end-user data it sends is handled at the destination; (5) change the destination or the characteristics of the data during the session; and (6) transmit status or user information about the destination (for example, whether it is a program or a device) between session partners.