A Data Over Cable Service Interface Specification (DOCSIS) cable modem system is coupled to: i) via a local area internet protocol (IP) network, a voice over internet protocol (VoIP) device operating Session Initiation Protocol (SIP) for signaling a VoIP session; and ii) via a DOCSIS network, a cable modem termination system (CMTS) via a network. The cable modem system comprises instructions stored in a memory and executed by a processor. The instructions comprise: i) in response to receiving a frame via the local area IP network, determining if the frame is a Session Initiation Protocol (SIP) invite message signaling a VoIP session with a remote endpoint; and ii) in response to determining that the frame is a SIP invite message, generating a DOCSIS message to the CMTS to request an addition of reserved bandwidth on the DOCSIS network for the VoIP session.