NNID is a system used for identifying and processing various network elements and services. 

• Identification in Networks: Similar to other numbering and identification systems in telecommunications, NNID is likely used for identifying network entities or elements. This identification is crucial for the correct routing and billing of calls, as well as for providing various network services.

• Use in Routing and Billing: NNID could play a role in routing calls to the appropriate destinations and in determining the correct billing procedures, especially in complex networks involving multiple carriers and service providers.

• Integration with Other Systems: Systems like NNID are typically integrated with a telecom operator's overall network infrastructure, working in conjunction with other technologies like Signal Transfer Points (STPs), Service Control Points (SCPs), and databases like the Home Location Register (HLR).

• Support for Various Services: NNID might support a range of telecommunication services, including voice calls, messaging services, and possibly data services.

While "NetNumber Identification" isn't a widely recognized standard term in public telecommunications literature, the concept of network identification and management is fundamental in ensuring the efficiency and reliability of telecommunication services.