The Total Network Data System/Trunking (TNDS/TK) systems are those modules of TNDS that support the engineering and administration of the message trunk network. TNDS/TK consists of the Trunk Forecasting System (TFS), the Trunk Servicing System (TSS), and Common Update/Trunking (CU/TK). Using representative trunk group loads and switching system growth data as input, TFS forecasts trunk needs for ... [Show full abstract] five future years. TSS fine tunes the first year of the forecast by showing where to rearrange the network to meet current demand. And CU/TK supports TSS and TFS with a record base that contains a description of the network and user-stated parameters. We describe TNDS/TK from the standpoint of its environment, functions, system internals, and future direction. We also present a high-level view of its algorithms. For more detail, the reader is referred to the “Theoretical and Engineering Foundations” article and its references in this issue.