This term is especially relevant in scenarios where services are provided through partnerships or reselling agreements. 

• Network Ownership: The ULC owns and maintains the actual network infrastructure, including physical cables (like fiber optics), network switches, cellular towers, and other necessary hardware for providing telecommunication services.

• Wholesale Services: Underlying Carriers often provide wholesale services to other telecom companies, which then offer retail services to end customers. These retail service providers may not own network infrastructure themselves and rely on ULCs.

• Partnerships and Agreements: Retail service providers enter into agreements with Underlying Carriers to use their networks. This arrangement allows them to offer services in areas where they don't have their own infrastructure.

• Quality and Reliability: The quality, coverage, and reliability of the services offered by retail providers are largely dependent on the capabilities and maintenance of the Underlying Carrier's network.

• Regulatory Compliance: ULCs are typically subject to regulatory standards and must ensure their infrastructure complies with national and international telecommunications regulations.

Understanding the role of Underlying Carriers is important in the telecom industry, particularly in how it affects service availability, network quality, and the dynamics of competition among telecom service providers.