Huawei Quidway S9300 Configuration Manual page 218

Quidway S9300 Terabit Routing Switch
Configuration Guide - Device Management
Concepts of 1588v2
PTP (Precision Time Protocol) is short for 1588, which is defined by the Institute of Electrical
and Electronics Engineers (IEEE). IEEE 1588 is a standard for Precision Clock Synchronization
Protocol For Networked Measurement and Control Systems. IEEE 1588v2 is defined as a time
synchronization protocol. IEEE 1588v2 ensures high-precision time synchronization between
devices, and now is also used in clock synchronization between devices.
A physical network can be logically divided into multiple clock domains. In each clock domain,
there is synchronized time, with which all devices in the domain are synchronized. The
synchronized time of one clock domain is independent of that of another clock domain.
Each node on a time synchronization network is called a clock. 1588v2 defines the following
types of clocks:
l
l
l
Besides the three basic types of the clock, the S9300 supports the following compound types of
clocks:
l
l
In the entire 1588v2 system, all clocks are organized according to the master-slave
synchronization hierarchy, with the grandmaster clock at the top of the hierarchy. Clock
Issue 03 (2011-12-29)
Ordinary clock
An ordinary clock (OC) has only one 1588v2 port, through which the local clock is
synchronized with an upstream 1588-aware node or distributes time signals to downstream
1588-aware nodes.
Boundary clock
A boundary clock (BC) has multiple 1588v2 ports. One port is synchronized with an
upstream 1588-aware node and the others distribute time signals to downstream 1588-
aware nodes.
In the case that a device obtains the standard time through an external non-1588v2 port
from a BITS device and distributes the time to downstream nodes through two 1588v2
ports. As the device has more than one 1588v2 port, the device is called a BC.
Transparent clock
Distinct from BC and OC that need to be synchronized with other clocks, TC does not need
to be synchronized with other clocks. A TC has multiple 1588v2 ports, through which
1588v2 packets are forwarded. In addition, the TC corrects forwarding delays for these
1588v2 packets and is not synchronized with other clocks through any port.
TC are classified into end-to-end (E2E) TC and peer-to-peer (P2P) TC.
– End-to-end transparent clock (E2ETC): directly forwards all 1588v2 packets on the
network, and participates in the calculation of the delay of the entire link.
– Peer-to-peer transparent clock (P2PTC): directly forwards Sync and Announce packets
on the network, terminates the remaining 1588v2 packets, and participates in calculating
the delay of each segment of the entire link.
TCOC: carries the characteristics of both a TC and an OC. A TCOC provides multiple ports
for communicating with the 1588v2 network. Among those ports, one is OC and the others
are TC. A TCOC implements 1588v2 frequency synchronization instead of time
synchronization.
TCandBC: carries the characteristics of both TC and BC. A TCandBC provides multiple
ports for communicating with the 1588v2 network. Among those ports, some are TC and
the others are BC. A TCandBC implements 1588v2 frequency synchronization and time
synchronization. The domain value of BC ports is the same as the 1588v2 domain value
configured in the system view.
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