# US 2020/0287784 A1 · Priority based selection of time services > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0287784 A1 - Document ID: US20200287784A1 - Status: Published application - Kind: A1 - Application number: 16/296,434 - Filed: 2019-03-08 - Published: 2020-09-10 - Earliest claimed: 2019-03-08 - Assignees: Cisco Technology, Inc. - Applicants: Cisco Technology, Inc. - Inventors: Eliot Lear - Web page: https://patentgrep.com/patent/US20200287784A1 ## CPC - H04J 3/0641: {Change of the master or reference, e.g. take-over or failure of the master} - H04L 41/0806: for initial configuration or provisioning, e.g. plug-and-play - H04L 12/18: for broadcast or conference {, e.g. multicast} - H04L 61/5014: using dynamic host configuration protocol [DHCP] or bootstrap protocol [BOOTP] - H04L 67/104: Peer-to-peer [P2P] networks - 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 In an embodiment, a method comprises at a network device in an enterprise network, selecting one or more time servers used for establishing a timing reference according to a predetermined priority order of selection that begins with determining whether the network device is configured with information indicating one or more time servers to be used. A timing reference is established for the network device based on a selected time server. ## Claims ### Claim 1 A method comprising: at a network device in an enterprise network, selecting one or more time servers used for establishing a timing reference according to a predetermined priority order of selection that begins with determining whether the network device is configured with information indicating one or more time servers to be used; and establishing a timing reference for the network device based on a selected time server. ### Claim 2 (depends on 1) The method of claim 1, wherein selecting according to the predetermined priority order of selection includes: if the network device is not configured with information indicating one or more time servers: sending a request through the enterprise network to a network management protocol server to receive time server identification information of one or more time servers used by the network management protocol server; and if the time server identification information is received, selecting at least one of the one or more time servers used by the network management protocol server. ### Claim 3 (depends on 2) The method of claim 2, wherein the network management protocol server is Dynamic Host Configuration Protocol server, and the request includes a network time protocol server option. ### Claim 4 (depends on 2) The method of claim 2, wherein selecting according to the predetermined priority order of selection includes: if the network device is not successful at selecting a time server based on the network management protocol server: sending into the enterprise network a multicast request for a network time protocol service; and if a response to the multicast request is received by the network device, selecting a time server based on information contained in the response to the multicast request. ### Claim 5 (depends on 4) The method of claim 4, wherein selecting according to the predetermined priority order of selection includes: if the network device is not successful at selecting a time server based on the multicast request: sending into the enterprise network a link layer protocol request for a network time protocol service; and if a response is received to the link layer protocol request, selecting a time server based on information contained in the response to the link layer protocol request. ### Claim 6 (depends on 5) The method of claim 5, wherein selecting according to the predetermined priority order of selection includes: if the network device is not successful at selecting a time server based on the link layer protocol request: attempting to connect to an Internet network time protocol server. ### Claim 7 (depends on 6) The method of claim 6, wherein selecting according to the predetermined priority order of selection includes: if the network device is not successful at connecting to the Internet network time protocol server: detecting network time protocol packets sent via multicast into the enterprise network by one or more peer network devices. ### Claim 8 (depends on 1) The method of claim 1, wherein selecting according to the predetermined priority order of selection includes: if the network device is not configured with information indicating one or more time servers: sending into the enterprise network a multicast request for a network time protocol service; and if a response to the multicast request is received by the network device, selecting a time server based on information contained in the response to the multicast request. ### Claim 9 A network device comprising: a network interface configured to enable network communications in a network by sending packets into the network or receiving packets from the network; a processor coupled to the network interface, the processor configured to: select one or more time servers used for establishing a timing reference for the network device according to a predetermined priority order of selection that begins with determining whether the network device is configured with information indicating one or more time servers to be used; and establish a timing reference for the network device based on a selected time server. ### Claim 10 (depends on 9) The network device of claim 9, wherein the processor is configured to: if the network device is not configured with information indicating one or more time servers: cause a request to be sent into the network to a network management protocol server to receive time server identification information of one or more time servers used by the network management protocol server; and if the time server identification information is received, select at least one of the one or more time servers used by the network management protocol server. ### Claim 11 (depends on 10) The network device of claim 10, wherein the processor is configured to: if the network device is not successful at selecting a time server based on the network management protocol server: send into the network a multicast request for a network time protocol service; and if a response to the multicast request is received by the network device, select a time server based on information contained in the response to the multicast request. ### Claim 12 (depends on 11) The network device of claim 11, wherein the processor is configured to: if the network device is not successful at selecting a time server based on the multicast request: send into the network a link layer protocol request for a network time protocol service; and if a response is received to the link layer protocol request, selecting a time server based on information contained in the response to the link layer protocol request. ### Claim 13 (depends on 12) The network device of claim 12, wherein the processor is configured to: if the network device is not successful at selecting a time server based on the link layer protocol request: attempt to connect to an Internet network time protocol server. ### Claim 14 (depends on 13) The network device of claim 13, wherein the processor is configured to: if the network device is not successful at connecting to the Internet network time protocol server: detect network time protocol packets sent via multicast into the network by one or more peer network devices. ### Claim 15 One or more non-transitory computer readable storage media encoded with instructions that, when executed by a processor, cause the processor to: at a network device in an enterprise network, select one or more time servers used for establishing a timing reference according to a predetermined priority order of selection that begins with determining whether the network device is configured with information indicating one or more time servers to be used; and establish a timing reference for the network device based on a selected time server. ### Claim 16 (depends on 15) The non-transitory computer readable storage media of claim 15, wherein instructions to select according to the predetermined priority order of selection includes instructions to: if the network device is not configured with information indicating one or more time servers: send a request through the enterprise network to a network management protocol server to receive time server identification information of one or more time servers used by the network management protocol server; and if the time server identification information is received, select at least one of the one or more time servers used by the network management protocol server. ### Claim 17 (depends on 16) The non-transitory computer readable storage media of claim 16, wherein instructions to select according to the predetermined priority order of selection includes instructions to: if the network device is not successful at selecting a time server based on the network management protocol server: send into the enterprise network a multicast request for a network time protocol service; and if a response to the multicast request is received by the network device, select a time server based on information contained in the response to the multicast request. ### Claim 18 (depends on 17) The non-transitory computer readable storage media of claim 17, wherein instructions to select according to the predetermined priority order of selection includes instructions to: if the network device is not successful at selecting a time server based on the multicast request: send into the enterprise network a link layer protocol request for a network time protocol service; and if a response is received to the link layer protocol request, select a time server based on information contained in the response to the link layer protocol request. ### Claim 19 (depends on 18) The non-transitory computer readable storage media of claim 18, wherein instructions to select according to the predetermined priority order of selection includes instructions to: if the network device is not successful at selecting a time server based on the link layer protocol request: attempt to connect to an Internet network time protocol server. ### Claim 20 (depends on 19) The non-transitory computer readable storage media of claim 19, wherein instructions to select according to the predetermined priority order of selection includes instructions to: if the network device is not successful at connecting to the Internet network time protocol server: detect network time protocol packets sent via multicast into the enterprise network by one or more peer network devices.