Timestamp predictor for packets over a synchronous protocol
A physical layer communication device (PHY) transmits and receives signal to and from a communication link using a synchronous protocol. The PHY communicates with a higher-layer device using a packet protocol. Timestamp values contained in timing-related messages in some packets are written or modified by the PHY. Delays incurred in transmitting and receiving the packets are predicted and used in setting the timestamp values.
1. A transmission device, comprising:
first circuitry configured to update timestamp fields contained in timing-related messages contained in at least some packets received by the first circuitry utilizing at least predicted delays, wherein updating the timestamp field comprises determining the predicted delay and writing information regarding the predicted delay into the timestamp field;
second circuitry configured to process the packet according to a packet protocol and adapt the at least some packets, received from said first circuitry and comprising said updated timestamp fields, from the packet protocol to a synchronous protocol, the second circuitry coupled to the first circuitry, the second circuitry further configured to transmit a signal formatted according to the synchronous protocol containing the at least some packets, the second circuitry comprising a buffer configured to match data rates between the packet protocol and the synchronous protocol; and
third circuitry configured to predict the delays that will be incurred by the at least some packets in the second circuitry, based on delay related information from the second circuitry, said delay related information responsive to the present state of the second circuitry, the present state of the second circuitry comprising a status of the second circuitry buffer, and supply the predicted delays to the first circuitry configured to update timestamp fields,
wherein said delay prediction comprises determining a delay that will be incurred in processing the packet according to the packet protocol and determining a delay that will be incurred in adapting the packet for transmission using the synchronous protocol.
2. The transmission device of claim 1 , wherein the present state of the second circuitry further comprises timings of the at least some packets in relation to timings of overhead sections in the signal formatted according to the synchronous protocol.
3. A method of processing a timing-related message, the method comprising:
receiving a packet containing the timing-related message, the packet formatted according to a packet protocol;
predicting a delay to be incurred in a transmit processing block arranged to adapt the packet for transmission using a synchronous protocol and in transmitting the packet, said delay prediction responsive to the present state of the transmit processing block;
updating a timestamp field in the timing-related message in the packet based on the predicted delay, wherein updating the timestamp field comprises determining the predicted delay and writing information regarding the predicted delay into the timestamp field;
after updating the timestamp field based on the predicted delay, processing the packet according to the packet protocol and adapting the packet containing the updated timestamp field for transmission using a synchronous protocol, said adapting performed by the transmit processing block, wherein the present state of the transmit processing block comprises a status of a buffer used for matching data rates between the packet protocol and the synchronous protocol; and
transmitting, via the transmit processing block, the adapted packet using the synchronous protocol,
wherein said delay prediction responsive to the present state of the transmit processing block further comprises determining a delay that will be incurred in processing the packet according to the packet protocol and determining a delay that will be incurred in adapting the packet for transmission using the synchronous protocol.
4. The method of claim 3 , the present state of the transmit processing block further comprises a state of adapting the packet for transmission using the synchronous protocol.
5. The method of claim 4 , wherein the state of adapting the packet comprises a timing of the packet in relation to a timing of an overhead section in the synchronous protocol.
6. The method of claim 3 , wherein receiving the packet comprises receiving the packet on a parallel bus, and wherein the present state of the transmit processing block further comprises a location of a portion of the packet on the parallel bus.
7. The method of claim 3 , wherein updating the timestamp field comprises calculating a predicted transmission time using the predicted delay and adding the predicted transmission time to a value in the timestamp field.
8. The method of claim 3 , further comprising receiving a time value, and wherein said writing information regarding the predicted delay comprises adding the time value and the predicted delay and writing said added value into the timestamp field.