1. A cable modem integrated session boarder control circuit coupled to a voice over internet protocol (VoIP) device via a local area network and coupled to a cable modem termination system (CMTS) via a Data-Over-Cable Service Interface Specification (DOCSIS) network, the cable modem integrated session border controller comprising: a cable modem circuit (CM) for communication with the CMTS; and a session border control circuit comprising instructions stored in a memory and executed by a processor, the instructions comprising: in response to receiving a frame via the local area network, the frame being a Session Initiation Protocol (SIP) message which includes identification of a destination VoIP device; using the identification of the destination VoIP device to determine whether a service flow over the DOCSIS network is required to support a real time protocol (RTP) stream of a VoIP session with the destination VoIP device; in response to determining that a service flow over the DOCSIS network is required to support an RTP stream of a VoIP session with the destination VoIP device, generating a message to the CMTS, the message including a request to reserve bandwidth on the DOCSIS network for the VoIP session; in response to receipt of a SIP OK message, generating a message to the CMTS, the message including a change of reserved bandwidth request to perform an action selected from a group of actions consisting of: establishing an additional unsolicited grant (UGS) sub flow within an existing service flow to support the RTP stream of the VoIP session; and establishing an additional (UGS) service flow within the reserved bandwidth to support the RTP stream of the VoIP session.