Configuring Ptp; Overview; Basic Concepts - H3C SR6600-X Configuration Manual

Configuring PTP

Overview

Precision Time Protocol (PTP) synchronizes time among devices. It provides greater accuracy than other
time synchronization protocols such as NTP. For more information about NTP, see "Configuring NTP."

Basic concepts

PTP profile
A PTP profile defines the following PTP standards:
IEEE 1588 version 2—1588v2 defines high-accuracy clock synchronization mechanisms. It can be
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customized, enhanced, or tailored as needed. 1588v2 is the latest version.
• IEEE 802.1AS—802.1AS is introduced based on IEEE 1588. It specifies a profile for use of IEEE
1588-2008 for time synchronization over a virtual bridged local area network (as defined by IEEE
802.1Q). The BMC algorithm in 802.1AS supports only the peer delay mode, and point-to-point
full-duplex Ethernet, IEEE 802.1 1, and IEEE 802.3 EPON links.
PTP domain
A PTP domain refers to a network that is enabled with PTP. A PTP domain has only one reference clock
called "grandmaster clock (GM)." All devices in the domain synchronize to the clock.
Clock node and PTP port
A node in a PTP domain is a clock node. A port enabled with PTP is a PTP port. PTP defines the following
types of basic clock nodes:
Ordinary Clock (OC)—A PTP clock with a single PTP port in a PTP domain for time synchronization.
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It synchronizes time from its upstream clock node through the port. If a clock node works as the clock
source and sends synchronization time through a single PTP port to its downstream clock node, it is
also called an OC.
• Boundary Clock (BC)—A clock with more than one PTP port in a PTP domain for time
synchronization. A BC uses one of the ports to synchronize time from its upstream clock node. It uses
the other ports to synchronize time to the relevant upstream clock nodes. If a clock node works as
the clock source and synchronizes time through multiple PTP ports to its downstream clock nodes, it
is also called a BC, such as BC 1 in
Transparent Clock (TC)—A TC does not need to keep time consistency with other clock nodes. A TC
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has multiple PTP ports. It only forwards PTP messages among these ports and performs delay
corrections for the messages, instead of performing time synchronization. TCs include the following
types:
End-to-End Transparent Clock (E2ETC)—Forwards non-P2P packets in the network and
calculates the delay of the entire link.
Peer-to-Peer Transparent Clock (P2PTC)—Forwards only Sync, Follow_Up, and Announce
messages, terminates other PTP messages, and calculates the delay of each link segment.
Figure 42 shows the positions of these types of clock nodes in a PTP domain.
Figure 42.
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