What product defines the protocols for IP telephony over HFC networks?

The correct answer is PacketCable. This is a standard developed by CableLabs that defines the required protocols for voice services over cable networks using a DOCSIS (Data Over Cable Service Interface Specification) infrastructure. PacketCable specifically addresses the transmission of telephony and multimedia services over hybrid fiber-coaxial (HFC) networks, ensuring reliability and quality of service in voice communication.

By defining how data packets that represent telephone calls are transmitted over these networks, PacketCable enables seamless integration of voice over IP (VoIP) technology, which is crucial for IP telephony services. This standard encompasses various components including signaling, network architecture, and quality assurance, making it essential for implementing voice services on cable networks.

The other options do not specifically target the integration and definition of protocols for telephony over HFC networks. For example, the Telephony Interface Standard (TIS) focuses more on interface specifications rather than network protocols, and Unified Communications Protocol (UCP) relates to broader unified communications rather than specifically to IP telephony over HFC. VoIP Network Protocol (VNP) is a term that might encompass various VoIP technologies, but it does not have the specific frameworks and definitions provided by PacketCable for use in HFC networks.