tination points concerned or to restore normal routing. 2. In conjunction with modifications of message routing, to control the resulting trans- fer of signaling traffic in a manner that avoids irregularities in message flow. 3. Flow control. Control of message routing is based on analysis of predetermined information about all allowed potential routing possibilities in combination with information, supplied by the signaling link management and signaling route management functions, about the status of the signaling network (i.e., current availability of signaling links and routes). Changes in the status of the signaling network typically result in modification of cur- rent message routing and thus in the transfer of certain portions of the signaling traffic from one link to another. The transfer of signaling traffic is performed in accordance with specific procedures. These procedures are changeover, changeback, forced rerouting, and controlled rerouting. The procedures are designed to avoid, as far as circumstances permit, such irregularities in message transfer as loss, missequencing, or multiple delivery of messages. The changeover and changeback procedures involve communication with other signal- ing point(s). For example, in the case of changeover from a failing signaling link, the two ends of the failing link exchange information (via an alternative path) that normally enables retrieval of messages that otherwise would have been lost on the failing link. A signaling network has to have a signaling traffic capacity that is higher than the normal traffic offered. However, in overload conditions (e.g., due to network failures or extremely high traffic peaks) the signaling traffic management function takes flow control actions to minimize the problem. An example is the provision of an indication 14.5 THE SIGNALING DATA LINK LAYER (LAYER 1) to the local user functions concerned that the MTP is unable to transport messages to a particular destination in the case of total breakdown of all signaling routes to that 