Abstract: A method for defining a payload format in Real Time Protocol (RTP) messages for voice band data transmission to be transmitted over a packet network to an Internet Protocol (IP) telephony endpoint, such as an IP phone. The invention extends RFC 2833 standards for Real Time Protocol (RTP) message payload format to include voice data transmission. The invention includes receiving voice transmission signals containing a voice band data from the public switched telephone network into a packet network and converting said voice transmission signals into data packets using real time protocol (RTP) and assigning an RTP event code in the RTP payload format for the voice band data applications. Applications include Caller Identification (Caller-ID), Visual Message Waiting Indication (VMWI), and Advanced Digital Subscriber Interface (ADSI).

Abstract: A technique is described to change the codec or MAC (message authentication code) size in a packet security unit for PacketCable communications during realtime voice transmissions is described. An algorithm that provides fast RC4 key advancing to prevent MIPS (millions of instruction cycles per second) overflow is used to perform codec or MAC size changes. The invention is performed without changing the keying material, where the sender and receiver must continue the RC4 encryption process from its state prior to the codec or MAC size change. A sender needs to preserve continuity of the timestamp across a codec change, since the timestamp reflects realtime. Changing the codec or MAC size is likely to change the frame parameters. To preserve continuity of the RC4 state and the timestamp across the codec/MAC size change, the sender TX and receiver RX generates a new frame number. The new frame number is applied to the first frame generated by the new codec or MAC size.

Abstract: The transport of ABCD bits in a digital packet network is facilitated by the inclusion of the ABCD bits into the RTP header of the digital packets. The ABCD bits are first placed in the unused bits of the RTP header. Redundancy of the previous ABCD bits, when applicable, is achieved by restricting the size of fields in the header to reserve space for redundant ABCD bits. The ABCD bits are placed in the reserved portions of restricted header fields.

Abstract: Packet production by a digital signal processor (DSP) is synchronized with modem transmission opportunities in a cable network. The cable modem computes the average waiting time a packet spends waiting to be transmitted by the modem. The DSP re-syncs transfer of packets to the modem by using this average waiting time minus a small amount sufficient to account for the maximum anticipated propagation delay, as the amount to delay the transmission of its next packet to the cable modem. This invention is a mechanism for re-synchronization that is largely independent of any propagation delays inherent in the hardware architecture.