- play_arrow Overview
- play_arrow Precision Time Protocol
- play_arrow Precision Time Protocol Overview
- play_arrow Precision Time Protocol Clocks
- PTP Boundary Clock Overview
- Example: Configure PTP Boundary Clock
- Example: Configure PTP Boundary Clock With Unicast Negotiation
- Configure PTP TimeTransmitter Clock
- Configure PTP TimeReceiver Clock
- Example: Configure Ordinary TimeReceiver Clock With Unicast-Negotiation
- Example: Configure Ordinary TimeReceiver Clock Without Unicast-Negotiation
- PTP Transparent Clocks
- Configure PTP Transparent Clock
- play_arrow Precision Time Protocol Profiles
- play_arrow PHY Timestamping
- play_arrow Precision Time Protocol over Ethernet
- PTP over Ethernet Overview
- Guidelines to Configure PTP over Ethernet
- Configure PTP Dynamic Ports for Ethernet Encapsulation
- Configure PTP Multicast TimeTransmitter and TimeReceiver Ports for Ethernet Encapsulation
- Example: Configure PTP over Ethernet for Multicast TimeTransmitter, TimeReceiver, and Dynamic Ports
- play_arrow Precision Time Protocol Additional Features
- Precision Time Protocol (PTP) over Link Aggregation Group (LAG)
- Precision Time Protocol (PTP) Trace Overview
- Line Card Redundancy for PTP
- Timing Defects and Event Management on Routing Platforms
- SNMP MIB for Timing on Routing Platforms
- PTP Passive Port Performance Monitoring on PTX10004 and PTX10008 Devices
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- play_arrow Global Navigation Satellite System (GNSS)
- play_arrow GPS Systems on Routing Platforms
- play_arrow Integrated GNSS on Routing Platforms
- play_arrow GNSS Configuration for Routers Using External GNSS Receiver
- play_arrow Assisted Partial Timing Support (APTS) on Routing Platforms
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- play_arrow Synchronous Ethernet
- play_arrow Synchronous Ethernet Overview
- play_arrow Synchronous Ethernet on 10-Gigabit Ethernet MIC
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- play_arrow Clock Synchronization
- play_arrow Clock Synchronization Concepts
- play_arrow Clock Synchronization for ACX Series Routers
- play_arrow Clock Synchronization for MX Series Routers
- play_arrow Clock Synchronization for PTX Series Routers
- play_arrow Centralized Clocking
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- play_arrow Hybrid Mode
- play_arrow Hybrid Mode Overview
- play_arrow Hybrid Mode and ESMC Quality-Level Mapping
- Configure Hybrid Mode and ESMC Quality-Level Mapping Overview
- Configure Hybrid Mode with Mapping of the PTP Clock Class to the ESMC Quality-Level
- Configure Hybrid Mode with a User-Defined Mapping of the PTP Clock Class to the ESMC Quality-Level
- Example: Configure Hybrid Mode and ESMC Quality-Level Mapping on ACX Series Router
- Example: Configure Hybrid Mode and ESMC Quality-Level Mapping on MX240 Router
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- play_arrow Configuration Statements and Operational Commands
- play_arrow Appendix
Network Time Protocol
Network Time Protocol (NTP) is a protocol used to synchronize time on all the devices in a network.
NTP Overview
Network Time Protocol (NTP) is a widely used protocol used to synchronize the clocks of routers and other hardware devices on the Internet. Primary NTP servers are synchronized to a reference clock directly traceable to Coordinated Universal Time (UTC). Reference clocks include GPS receivers and telephone modem services, NTP accuracy expectations depend on the environment application requirements. However, NTP can generally maintain time to within tens of milliseconds over the public internet.
NTP is defined in the RFC 5905: Network Time Protocol Version 4: Protocol and Algorithms Specification
Devices running Junos OS can be configured to act as an NTP client, a secondary NTP server, or a primary NTP server. These variations are as follows:
Primary NTP Server—Primary NTP servers are synchronized to a reference clock that is directly traceable to UTC. These servers then re-distribute this time data downstream to other Secondary NTP servers or NTP clients.
Secondary NTP Server—Secondary NTP servers are synchronized to a primary or secondary NTP server. These servers then re-distribute this data downstream to other Secondary NTP servers or NTP clients.
NTP Client—NTP clients are synchronized to a primary or secondary NTP server. Clients do not re-distribute this time data to other devices.
The NTP subnet includes a number of widely accessible public primary time servers that can be used as a network’s primary NTP server. Juniper Networks strongly recommends that you authenticate any primary servers you use.
Each device on your network can be configured to run in one or more of the following NTP modes:
Broadcast Mode—One or more devices is set up to transmit time information to a specified broadcast or multicast address. Other devices listen for time sync packets on these addresses. This mode is less accurate than the client/server mode.
Client/Server Mode—Devices are organized hierarchically across the network in client/server relationships.
Symmetric Active (peer) Mode—Two or more devices are configured as NTP server peers to provide redundancy.
By default, if an NTP client time drifts so that the difference in time from the NTP
server exceeds 128 milliseconds, the NTP client is automatically stepped back into
synchronization. The NTP client will still synchronize with the server even if the
offset between the NTP client and server exceeds the 1000-second threshold. You can
manually request that a device synchronize with an NTP server by using the
set date ntp operational command on the router. On devices
running Junos OS that have dual Routing Engines, the backup Routing Engine
synchronizes directly with the primary Routing Engine.
All Juniper platforms that run Junos OS support the leap second adjustment. By default, if the NTP server is aware of the leap second calculations, then the Junos device will automatically add the 1 second delay. PTP (Precision Time Protocol) is used to detect and propagate leap second synchronization changes throughout all nodes in a network. NTP is also required for Common Criteria compliance.
For more details about the Network Time Protocol, go to the Network Time Foundation website at http://www.ntp.org.
NTP supports IPv4 VPN and IPv6 routing and forwarding (VRF) requests on Junos OS. VRF request is also supported on Junos OS Evolved Release 20.2R1 onwards. This enables an NTP server running on a provider edge (PE) router to respond to NTP requests from a customer edge (CE) router. As a result, a PE router can process any NTP request packet coming from different routing instances.
