# US 12,120,212 B2 · Time recovery in a time sensitive network > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,120,212 B2 - Document ID: US12120212B2 - Status: Granted - Kind: B2 - Application number: 17/706,939 - Filed: 2022-03-29 - Published: 2022-07-14 - Granted: 2024-10-15 - Earliest claimed: 2022-03-29 - Assignees: Intel Corporation - Applicants: Intel Corporation - Inventors: Vuk Lesi; Christopher Gutierrez; Manoj Sastry; Christopher Hall; Marcio Juliato; Shabbir Ahmed; Qian Wang - Web page: https://patentgrep.com/patent/US12120212B2 ## CPC - H04J 3/14: Monitoring arrangements {(for SDH/SONET rings H04J3/085)} - H04L 7/0016: {correction of synchronization errors} - H04J 3/06: Synchronising arrangements {(for television systems H04N5/04; bit-synchronisation H04L7/00)} - H04J 3/0673: {using intermediate nodes, e.g. modification of a received timestamp before further transmission to the next packet node, e.g. including internal delay time or residence time into the packet} - H04L 69/28: Timers or timing mechanisms used in protocols - H04J 3/0667: {Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays (arrangements for monitoring round trip delays in packet switching networks H04L43/0864)} - H04L 2463/121: Timestamp - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Time recovery techniques are described. A method comprises receiving messages from the first device by the second device in the first network domain, the messages to comprise time information to synchronize a first clock for the first device and a second clock for the second device to a network time, determining the second clock is to recover the network time for the second device without new messages from the first device, retrieving a first set of timestamps previously stored for events in the first network domain using the network time from the second clock, retrieving a second set of timestamps previously stored for the events in the first network domain using a redundant time from a third clock, where the third clock is not synchronized with the first and second clocks, and recovering the network time using a regression model and the redundant time from the third clock. ## Claims ### Claim 1 An apparatus, comprising: a processing circuitry; a memory coupled to the processing circuitry, the memory to store instructions that when executed by the processing circuitry causes the processing circuitry to: establish a data stream between a first device and a second device in a first network domain, the data stream comprising a plurality of switching nodes; receive messages from the first device by the second device in the first network domain, the messages to comprise time information to synchronize a first clock for the first device and a second clock for the second device to a network time for the first network domain; determine the second clock is to recover the network time for the second device without new messages from the first device; retrieve a first set of timestamps previously stored for events in the first network domain using the network time from the second clock; retrieve a second set of timestamps previously stored for the events in the first network domain using a redundant time from a third clock, wherein the third clock is not synchronized with the first and second clocks; construct a regression model based on the first and second set of timestamps; and recover the network time of the first network domain using a redundant time from the third clock as input for the regression model to output a recovered network time for the second clock of the second device. ### Claim 2 (depends on 1) The apparatus of claim 1, the processing circuitry to establish the data stream in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.1AS and/or 802.1Qbv and/or 1588 standards. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the messages are synchronization messages or follow up messages for a precision time protocol (PTP). ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the first device operates in a clock leader (CL) role and the second device operates in a clock follower (CF) role. ### Claim 5 (depends on 1) The apparatus of claim 1, the processing circuitry to determine the second clock is to recover the network time for the second device without new messages from the first device when the messages are not received by the second device for a defined time interval. ### Claim 6 (depends on 1) The apparatus of claim 1, the processing circuitry to store the first set of timestamps for events in the first network domain based on the network time from the second clock by the second device. ### Claim 7 (depends on 1) The apparatus of claim 1, the processing circuitry to recover the network time of the first network domain using the redundant time from the third clock as input for the regression model to output the recovered network time for the second clock of the second device, the processing circuitry to: receive a current redundant time from the third clock in the second network domain not synchronized with the first and second clocks; calculate a recovered network time with the regression model; synchronize the second clock of the second device to the recovered network time. ### Claim 8 (depends on 1) The apparatus of claim 1, the processing circuitry to send messages from the second device to a fourth device in the first network domain, the messages to comprise time information to synchronize the second clock for the second device and a fourth clock for the fourth device to the recovered network time, the second device to operate in the CL role and the fourth device to operate in the CF role. ### Claim 9 A computing-implemented method, comprising: establishing a data stream between a first device and a second device in a first network domain, the data stream comprising a plurality of switching nodes; receiving messages from the first device by the second device in the first network domain, the messages to comprise time information to synchronize a first clock for the first device and a second clock for the second device to a network time for the first network domain; determining the second clock is to recover the network time for the second device without new messages from the first device; retrieving a first set of timestamps previously stored for events in the first network domain using the network time from the second clock; retrieving a second set of timestamps previously stored for the events in the first network domain using a redundant time from a third clock, wherein the third clock is not synchronized with the first and second clocks; constructing a regression model based on the first and second set of timestamps; and recovering the network time of the first network domain using a redundant time from the third clock as input for the regression model to output a recovered network time for the second clock of the second device. ### Claim 10 (depends on 9) The computing-implemented method of claim 9, wherein the first device operates in a clock leader (CL) role and the second device operates in a clock follower (CF) role. ### Claim 11 (depends on 9) The computing-implemented method of claim 9, determining the second clock is to recover the network time for the second device without new messages from the first device in response to a message indicating the first device is under a security attack and placed in isolation from the first network domain. ### Claim 12 (depends on 9) The computing-implemented method of claim 9, wherein the redundant time from the third clock maintains a defined relationship with the network time from the second clock, the defined relationship to comprise an approximate linear relationship. ### Claim 13 (depends on 9) The computing-implemented method of claim 9, comprising storing the second set of timestamps for the events in the first network domain based on the redundant time from the third clock by a third device in a second network domain separate from the first network domain. ### Claim 14 (depends on 9) The computing-implemented method of claim 9, comprising recovering the network time of the first network domain using the redundant time from the third clock as input for the regression model to output the recovered network time for the second clock of the second device by: receiving a current redundant time from the third clock in the second network domain not synchronized with the first and second clocks; calculating a recovered network time with the regression model; synchronizing the second clock of the second device to the recovered network time. ### Claim 15 (depends on 9) The computing-implemented method of claim 9, comprising switching the second device from operating in the CF role to operating in the CL role for the first network domain. ### Claim 16 (depends on 9) The computing-implemented method of claim 9, comprising sending messages from the second device to a fourth device in the first network domain, the messages to comprise time information to synchronize the second clock for the second device and a fourth clock for the fourth device to the recovered network time, the second device to operate in the CL role and the fourth device to operate in the CF role. ### Claim 17 A non-transitory computer-readable storage device, storing instructions that when executed by processing circuitry of a manager of a time sensitive network (TSN), cause the manager to: receive messages from the first device by the second device in the first network domain, the messages to comprise time information to synchronize a first clock for the first device and a second clock for the second device to a network time for the first network domain; determine the second clock is to recover the network time for the second device without new messages from the first device; retrieve a first set of timestamps previously stored for events in the first network domain using the network time from the second clock; retrieve a second set of timestamps previously stored for the events in the first network domain using a redundant time from a third clock, wherein the third clock is not synchronized with the first and second clocks; construct a regression model based on the first and second set of timestamps; and recover the network time of the first network domain using a redundant time from the third: clock as input for the regression model to output a recovered network time for the second clock of the second device. ### Claim 18 (depends on 17) The computer-readable storage medium of claim 17, the instructions, when executed by the processing circuitry, cause the manager to establish the data stream in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.1AS and/or 802.1Qbv and/or 1588 standards. ### Claim 19 (depends on 17) The computer-readable storage medium of claim 17, wherein the messages are synchronization messages or follow up messages for a precision time protocol (PTP). ### Claim 20 (depends on 17) The computer-readable storage medium of claim 17, wherein the first device operates in a clock leader (CL) role and the second device operates in a clock follower (CF) role. ### Claim 21 (depends on 17) The computer-readable storage medium of claim 17, the instructions, when executed by the processing circuitry, cause the manager to determine the second clock is to recover the network time for the second device without new messages from the first device when the messages are not received by the second device for a defined time interval. ### Claim 22 (depends on 17) The computer-readable storage medium of claim 17, the instructions, when executed by the processing circuitry, cause the manager to store the first set of timestamps for events in the first network domain based on the network time from the second clock by the second device. ### Claim 23 (depends on 17) The computer-readable storage medium of claim 17, wherein the redundant time from the third clock maintains a defined relationship with the network time from the second clock, the defined relationship to comprise an approximate linear relationship. ### Claim 24 (depends on 17) The computer-readable storage medium of claim 17, the instructions, when executed by the processing circuitry, cause the manager to store the second set of timestamps for the events in the first network domain based on the redundant time from the third clock of the second device.