Physical layer processing of timestamps and MAC security
A physical layer device provides both timestamp processing and security processing. The timestamp processing may be PTP processing according to IEEE Std. 1588 and/or OAM processing according to ITU-T Recommendation Y.1731. The security processing may be MACsec processing according to IEEE Std. 802.1AE. The timestamp processing may delay some packets to avoid impairing accuracy of timing information. For example, the accuracy of timing information could be impaired when a packet containing the timing information is delay due to additional bits added to a preceding packet to include a security tag and integrity check value.
1. A method performed by a physical layer communication device implemented using electronic circuitry, the method comprising:
receiving a packet for transmission;
determining whether the packet is a packet that is to receive timestamp processing;
if the packet is to receive timestamp processing, determining a value indicative of a time of transmission of the packet to a communication network;
if the packet is to receive timestamp processing, inserting the value indicative of the time of transmission in to the packet;
if the packet is to receive timestamp processing, after determining the value indicative of the time of transmission, and after inserting the value indicative of the time of transmission into the packet, delaying the packet for a time interval to avoid having the packet incur a variable delay during subsequent processing due to Media Access Control Security (MACsec) processing of a prior packet, wherein the time interval is based on a time of transmission of a maximum number of bits that may be added to the prior packet for the MACsec processing; and
transmitting the packet over the communication network.
2. The method of claim 1 , wherein the time interval corresponds to a time that provides a minimum from the prior packet after the maximum number of bits that may be added to the prior packet for the MACsec processing.
3. The method of claim 1 , wherein the packet is received from a media access controller.
4. The method of claim 1 , wherein the determining whether the packet is a packet to receive time stamp processing utilizes values of source and destination addresses in the packet.
5. The method of claim 1 , wherein the determining whether the packet is a packet to receive time stamp processing utilizes values of tags in the packet.
6. The method of claim 1 , further comprising signaling transmit flow control circuitry when the packet is delayed.
7. The method of claim 1 , wherein the MACsec processing includes adding a security tag to the packet, and adding an integrity check value (ICV) to the packet.
8. The method of claim 7 , wherein the MACsec processing further includes encrypting at least payload data in the packet.
9. The method of claim 1 , further comprising providing the value indicative of time of transmission of the packet to a higher level device.
10. The method of claim 1 , further comprising inserting into the packet the value indicative of the time of transmission of the packet.
11. The method of claim 1 , further comprising:
determining if a received further packet, received from the communication network, is subject to the MACsec processing;
performing the MACsec processing of the received further packet; and
adjusting a time value from a local clock based on delays in performing the MACsec processing to provide a time of reception for the received further packet.
12. The method of claim 11 , wherein the time value is adjusted by a fixed amount.
13. A method performed by a physical layer device (PHY) comprising a transmit chain including a transmitter, a Media Access Control Security (MACsec) processing block, a timestamp processing block, and a flow control block, the method comprising:
buffering packets for transmission by the flow control block;
determining, by the timestamp processing block, whether packets for transmission are packets subject to timestamp processing;
timestamping the packets subject to timestamp processing by providing, by the timestamp processing block, for the packets subject to timestamp processing, an indication of predicted time of transmission of the packets from the PHY, including inserting the predicted time of transmission into the packets, wherein the predicted time of transmission is based on a current time and expected delays in the MACsec processing block and the transmitter;
subsequent to timestamping the packets, delaying, by the timestamp processing block, provision to the MACsec processing block of each of the timestamped packets for a time interval so as to reduce inaccuracy of the predicted time of transmission, wherein the time interval is based on a time of transmission of a maximum number of bits that may be added to a respective prior one of the timestamped packets for MACsec processing;
performing, by the MACsec processing block, the MACsec processing on at least some of the packets; and
transmitting, by the transmitter, the packets.
14. The method of claim 13 , wherein the indication of predicted time of transmission of the packets is provided to a higher level device.
15. The method of claim 13 , wherein the indication of predicted time of transmission of the packets is provided in the packet.
16. The method of claim 13 , further comprising providing, by the timestamp processing block, an indication that data transmission is extended.
17. The method of claim 13 , wherein the MACsec processing include adding an integrity check value (ICV) to the packets.
18. The method of claim 17 , wherein the MACsec processing include encrypting data of the packets.