g the underlying backbone over which traffic is delivered to a specific location in various configurations. Telecommunications Operations Map (TOM): A more detailed extension of the original TMN architecture developed by the TeleManagement Forum. The TOM incorporates business processes, transaction models and other elements critical to real-world TMN implementations. Time Division Multiplexing (TDM): A method for condensing network traffic that packages traffic streams into coordinated time slots for more efficient transmission across a network. TDM is the basis for traditional landline and mobile voice networks. Though long standing, TDM is not considered an extremely efficient scheme compared to others now available. The Telecommunications Management Network (TMN) model: A multi- tiered model, established by the ITU and further developed by the TeleManagement Forum, that provides guidelines for how OSS functions are grouped and how they should interact. Trivial File Transfer Protocol (TFTP): A lightweight file transfer protocol generally used in IP implementations on networks with limited capacity. Universal Mobile Telecommunications Systems (UMTS): A proposed, next- generation or 3G mobile network technology set that supports robust data capabilities in addition to digital voice services. The Ultimate Guide to Building and Delivering OSS/BSS Universal Standard Ordering Codes (USOCs): The numeric codes IICs, particularly incumbents, assign to identify different services and product offerings. Value-Added Networks (VANs): A general term for networks that have been purpose-built to support a specific business function. The older EDI-based networks some IICs use to exchange billing settlement data with other IICs can be considered VANs. User Acceptance Testing (UAT): The series of tests an IIC will run within its organization to measure how well its staff adapts to a new system or process implementation. Results derived from these tests are generally used to refine the OSS implementation to suit user needs. Virtua