# US 12,192,316 B2 · Method to eliminate clock synchronization from undesired clock sources > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,192,316 B2 - Document ID: US12192316B2 - Status: Granted - Kind: B2 - Application number: 17/558,313 - Filed: 2021-12-21 - Published: 2023-06-22 - Granted: 2025-01-07 - Earliest claimed: 2021-12-21 - Assignees: Cisco Technology, Inc. - Applicants: Cisco Technology, Inc. - Inventors: Sreejith Avikkal; Nancy Patricia Cam-Winget; Lizbeth Berenice Guerra Martinez; Natasha Wong; Jessica Lynne Poole - Web page: https://patentgrep.com/patent/US12192316B2 ## CPC - H04L 7/10: Arrangements for initial synchronisation - H04J 3/0641: {Change of the master or reference, e.g. take-over or failure of the master} - 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 9/3247: {involving digital signatures} - H04L 9/3297: {involving time stamps, e.g. generation of time stamps} - H04L 9/40: Network security protocols - H04L 63/08: {for authentication of entities (cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32)} - H04L 63/0876: {based on the identity of the terminal or configuration, e.g. MAC address, hardware or software configuration or device fingerprint} - H04L 63/101: {Access control lists [ACL]} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - 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) ## Abstract In one embodiment, methods for monitoring devices within a network by a controller are described. The method may include receiving a first request from a first device to authenticate a role of the first device as a grandmaster in a precision time protocol (PTP). Additionally, the method may include granting the first request designating the role of the first device as the grandmaster. The method may further include receiving a second request from a second device to authenticate that a clock announce message is from an authorized grandmaster. Additionally, the method may include determining whether the first device is authorized to send the clock announce message to the second device and, based on the determining, sending a message granting or denying permission for the first device to sync with the second device. ## Claims ### Claim 1 A method performed at least partly by a controller that monitors devices within a network, the method comprising: receiving a first request from a first device to authenticate a role of the first device as a grandmaster in a precision time protocol (PTP); granting the first request designating the role of the first device as the grandmaster; receiving a second request from a second device to authenticate that a clock announce message from the first device is from an authorized grandmaster; determining whether the first device is authorized to send the clock announce message to the second device; and in response to determining the first device is authorized to send the clock announce message, sending to the second device a message indicating that the first device is authorized as the grandmaster and granting permission for the second device to sync with the first device; or in response to determining that the first device is not authorized to perform the clock announce message, sending to the second device, a message indicating that the first device is not authorized as the grandmaster and denying permission for the second device to sync with the first device. ### Claim 2 (depends on 1) The method of claim 1, wherein the first request comprises a clock ID of the first device. ### Claim 3 (depends on 2) The method of claim 2, wherein granting the first request designating the role of the first device as the grandmaster further comprises: determining that the clock ID of the first device is included in a pool of permitted device IDs; and authenticating that the role of the grandmaster is a permitted role associated with the clock ID of the first device. ### Claim 4 (depends on 1) The method of claim 1, wherein granting the first request designating the role of the first device as the grandmaster further comprises: analyzing clock quality attributes associated with the first device, the clock quality attributes including at least one of a clock accuracy or a clock class; and determining that at least one of the clock accuracy or the clock class satisfies a clock quality threshold. ### Claim 5 (depends on 1) The method of claim 1, further comprising: receiving a third request from the second device to authenticate a role of the second device as a slave in the PTP; and granting the third request designating the role of the second device as the slave. ### Claim 6 (depends on 1) The method of claim 1, wherein granting the first request further comprises: providing the first device with a key in response to authenticating the role of the first device as the grandmaster, the key comprising a private key. ### Claim 7 (depends on 6) The method of claim 6, wherein the second request from the second device includes the key. ### Claim 8 (depends on 1) The method of claim 1, further comprising: receiving, from the second device and after a threshold period of time has elapsed, an authentication and authorization request to validate authenticity and authorization of the first device to act as the grandmaster; determining whether the first device is authenticated and authorized to act as the grandmaster; and in response to determining the first device is authenticated to act as the grandmaster, sending to the second device a second message indicating that the first device is authorized to act as the grandmaster and permitting the second device to continue syncing with the first device; or in response to determining that the first device is not authenticated or not authorized to act as the grandmaster, sending to the second device, a second message indicating that the first device is not authorized and denying permission for the second device to continue syncing with the first device. ### Claim 9 A system comprising: one or more processors; and one or more non-transitory computer-readable media storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising: receiving a first request from a first device to authenticate a role of the first device as a grandmaster in a PTP; granting the first request designating the role of the first device as the grandmaster; receiving a second request from a second device to authenticate that a clock announce message from the first device is from an authorized grandmaster; determining whether the first device is authorized to send the clock announce message to the second device; and in response to determining the first device is authorized to send the clock announce message, sending to the second device a message indicating that the first device is authorized as the grandmaster and granting permission for the second device to sync with the first device; or in response to determining that the first device is not authorized to perform the clock announce message, sending to the second device, a message indicating that the first device is not authorized as the grandmaster and denying permission for the second device to sync with the first device. ### Claim 10 (depends on 9) The system of claim 9, wherein the first request comprises a clock ID of the first device. ### Claim 11 (depends on 10) The system of claim 10, wherein granting the first request designating the role of the first device as the grandmaster further comprises: determining that the clock ID of the first device is included in a pool of permitted device IDs; and authenticating that the role of grandmaster is a permitted role associated with the clock ID of the first device. ### Claim 12 (depends on 9) The system of claim 9, wherein granting the first request designating the role of the first device as the grandmaster further comprises: analyzing clock quality attributes associated with the first device, the clock quality attributes including at least one of a clock accuracy or a clock class; and determining that at least one of the clock accuracy or the clock class satisfies a clock quality threshold. ### Claim 13 (depends on 9) The system of claim 9, the operations further comprising: receiving a third request from the second device to authenticate a role of the second device as a slave in the PTP; and granting the third request designating the role of the second device as the slave. ### Claim 14 (depends on 9) The system of claim 9, wherein granting the first request further comprises: providing the first device with a key in response to authenticating the role of the first device as the grandmaster, the key comprising a private key. ### Claim 15 (depends on 14) The system of claim 14, wherein the second request from the second device includes the key. ### Claim 16 (depends on 9) The system of claim 9, further comprising: receiving, from the second device and after a threshold period of time has elapsed, an authentication and authorization request to validate authenticity and authorization of the first device to act as the grandmaster; determining whether the first device is authenticated and authorized to act as the grandmaster; and in response to determining the first device is authenticated to act as the grandmaster, sending to the second device a second message indicating that the first device is authorized to act as the grandmaster and permitting the second device to continue syncing with the first device; or in response to determining that the first device is not authenticated or not authorized to act as the grandmaster, sending to the second device, a second message indicating that the first device is not authorized and denying permission for the second device to continue syncing with the first device. ### Claim 17 A network device comprising: one or more processors; and one or more non-transitory computer-readable media storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising: sending an authentication request to a controller of a network to designate a role of the network device as a grandmaster in a precision time protocol (PTP); receiving a grant of authentication from the controller designating the role of the network device as the grandmaster, wherein the grant of authentication comprises a private key; sending a secured clock announce message to a second device within the network; and performing a best master clock algorithm (BMCA) with the second device to synchronize a clock of the second device with a clock of the network device. ### Claim 18 (depends on 17) The network device of claim 17, wherein the secured clock announce message comprises a tag-length-value (TLV), the TLV comprising a proof of integrity that the network device is authenticated to act as the grandmaster. ### Claim 19 (depends on 18) The network device of claim 18, wherein the proof of integrity comprises a signature encrypted using the private key. ### Claim 20 (depends on 17) The network device of claim 17, wherein the secured clock announce message comprises the private key.