Signalling System Number 7 (SS7) - Message Transfer Part (MTP) - This standard is made up of eight chapters. Chapter T1.111.1 provides the functional description of the Message Transfer Part of Signalling system Number 7 (SS7). Chapter T1.111.2 describes signalling data link to be used for SS7 networks in the United States. Chapter T1.111.3 describes the functions and procedures for, and relating to, the transfer of signalling messages over one signalling data link. In this section, "signal units" of variable lengths are transferred, including control information for proper operation. Chapter T1.111.4 describes the functions and procedures for, and relating to, the transfer of messages between signalling points. These signalling network management functions ensure a reliable transfer of signalling messages, according to the requirements specified in Chapter T1.111.6. Chapter T1.111.5 describes aspects that are pertinent to , and should be considered in, the design requirements of the Message Transfer Part. The signalling performance is the capability of the Message Transfer Part to transfer messages of variable lengths for different users in a defined manner. Chapter T1.111.7 describes means and procedures for the testing and maintenance of the signalling network in order to realize the performance requirements for the Message Transfer Part, as identified in Chapter T1.111.6. Chapter T1.111.8 describes aspects that are pertinent to the numbering scheme of signalling codes for SS7 networks in the United States.