Method and apparatus for carrying constant bit rate (CBR) client signals

An integrated circuit (IC) device for an intermediate-network-node, comprising:

• a Physical Layer (PHY) link input to receive a data stream generated by a previous network node that includes a plurality of constant bit rate (CBR) carrier streams, respective ones of the CBR carrier streams including a previous network node cumulative phase offset report (CPOR-P) that indicates a previous network node cumulative phase offset (CPO-P) and a client rate report (CRR) that indicates a measured bit count of a respective CBR client at a source node;
• a clock offset circuit coupled to the PHY link input to sample a counter accumulating a PHY-scaled stream clock (IPSCk) at a nominal sampling period (Tps) of a local reference clock of the intermediate-network-node to obtain a cumulative PHY-scaled count (CPSC) of the received respective data stream, the IPSCk generated by scaling a clock recovered from the received respective data stream to a predetermined nominal frequency (Fipsck_nom) and to calculate a PHY-scaled stream phase offset (PSPO) that indicates the phase difference between a PHY-scaled stream nominal bit count (LPSD) and an incoming PHY-scaled count delta (IPSD), where the IPSD indicates an increment between successive CPSCs;
• a demultiplexer coupled to the PHY link input to demultiplex the received data stream to obtain the plurality of CBR carrier streams;
• a cumulative phase offset report (CPOR) update logic coupled to the demultiplexer and the clock offset circuit to calculate a cumulative phase offset (CPO) for respective ones of the CBR carrier streams, wherein the calculated CPO is a function of the CPO-P and the calculated PSPO, and to replace the CPO-P with the calculated CPO for the respective CBR carrier stream, or with a function of the calculated CPO for the respective CBR carrier stream, and to generate an updated CPOR for the respective CBR carrier stream in place of the CPOR-P in the respective CBR carrier stream;
• a multiplexer coupled to the demultiplexer and the CPOR update logic to multiplex the CBR carrier streams into a plurality of intermediate-network-node data streams;
• encoders coupled to the multiplexer to encode the plurality of intermediate-network-node data streams;
• and
• PHY link outputs coupled to the encoders to transmit the plurality of intermediate-network-node data streams from the IC device.

A network comprising:

• a source node that includes:
• an input to receive a plurality of constant bit rate (CBR) signals,
• a cumulative phase offset report (CPOR) generating circuit to generate a CPOR that indicates an initial cumulative phase offset (CPO),
• a CRR generating circuit to generate a client rate report (CRR) that indicates a measured bit rate of a respective CBR client, and
• a CBR mapper coupled to the input to generate for respective ones of the CBR signals a corresponding CBR carrier stream and to insert the CRR and CBR client data into a respective CBR carrier stream,
• a source output processing circuit to insert the CPOR into a respective CBR carrier stream and multiplex the CBR carrier streams to generate a plurality of source data streams;
• a plurality of intermediate-network-nodes coupled to the source node, respective ones of the intermediate-network-nodes comprising an integrated circuit (IC) device that includes:
• a Physical Layer (PHY) link input to receive a data stream generated by a previous network node that includes a plurality of CBR carrier streams, respective ones of the CBR carrier streams including a previous network node cumulative phase offset report (CPOR-P) that indicates a previous network node cumulative phase offset (CPO-P) and the CRR;
• a clock offset circuit coupled to the PHY link input to:
• sample a counter accumulating a PHY-scaled stream clock (IPSCk) at a nominal sampling period (Tps) of a local reference clock of the intermediate-network-node to obtain a cumulative PHY-scaled count (CPSC) of the received respective data stream, the IPSCk generated by scaling a clock recovered from the received respective data stream to a predetermined nominal frequency (Fipsck_nom), and
• calculate a PHY-scaled stream phase offset (PSPO) that indicates the phase difference between a PHY-scaled stream nominal bit count (LPSD) and an incoming PHY-scaled count delta (IPSD), where the IPSD indicates an increment between successive CPSCs;
• a demultiplexer coupled to the PHY link input to demultiplex the received data stream to obtain the individual CBR carrier streams,
• a cumulative phase offset report (CPOR) update logic coupled to the demultiplexer and the clock offset circuit to calculate a CPO for respective ones of the CBR carrier streams, wherein the calculated CPO is a function of the CPO-P for the particular CBR carrier stream and the calculated PSPO, and to replace the CPO-P for the particular CBR carrier stream with the calculated CPO for the respective CBR carrier stream to generate an updated CPOR for the respective CBR carrier stream in place of the CPOR-P for the particular CBR carrier stream,
• a multiplexer coupled to the demultiplexer and the CPOR update logic to multiplex the CBR carrier streams into a plurality of intermediate-network-node data streams,
• encoders coupled to the multiplexer to encode the plurality of intermediate-network-node data streams, and
• PHY link outputs coupled to the encoders to transmit the plurality of intermediate-network-node data streams from the IC device;
• and
• a sink node coupled to a last one of the intermediate-network-nodes for receiving an intermediate-network-node data stream from a last one of the intermediate-network-nodes, recovering CBR client signals and outputting from the sink node a CBR signal that includes the recovered CBR client signals.