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Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide
OL-16506-17
Chapter 12 IEEE 1588v2 PTP Support
Information About IEEE 1588v2 PTP
• IPv6 and Multiprotocol Label Switching (MPLS) encapsulation are not supported for PTP packet
transfer over Cisco ASR 1002-X Routers.
• The time-of-day recovered from a 1588v2 session does not synchronize with the system clock.
• GPS interfaces can be used only for clock recovery. You cannot transmit the system clock on the
GPS interface.
Information About IEEE 1588v2 PTP
IEEE 1588v2 PTP is a packet-based two-way message exchange protocol for synchronizing a local clock
with a primary reference clock or a grand master clock in hierarchical master-slave architecture. This
synchronization is achieved through packets that are transmitted and received in a session between a
master clock and a slave clock. IEEE 1588v2 PTP supports system-wide synchronization accuracy in the
sub-microsecond range with little use of network and local clock-computing resources.
The following sections describe the terminologies used for better understanding of the IEEE 1588v2
PTP.
PTP Clocks
PTP employs a hierarchy of clock types to ensure that precise timing and synchronization is maintained
between the source and the numerous PTP clients that are distributed throughout the network. A logical
grouping of PTP clocks that synchronize with each other using the PTP protocol, but are not necessarily
synchronized to the PTP clocks in another domain, is called a PTP domain.
The three PTP clock types are Ordinary clock, Boundary clock, and Transparent clock.
• Ordinary clock--This clock type has a single PTP port in a domain, and maintains the timescale
used in the domain. It may serve as a source of time, that is, be a master, or may synchronize to
another clock by being a slave. It provides time to an application or to an end device.
• Boundary clock--This clock type has multiple PTP ports in a domain, and maintains the timescale
used in the domain. It may serve as a source of time, that is, be a master, or may synchronize to
another clock by being a slave. A boundary clock that is a slave has a single slave port, and transfers
timing from that port to the master ports.
• Transparent clock--This clock type is a device that measures the time taken for a PTP event
message to pass through the device, and provides this information to the clocks receiving this PTP
event message.
Table 15-1 shows the 1588v2 PTP support matrix on a Cisco ASR1000 platform.
Components of a PTP-enabled Network
The three key components of a PTP-enabled data network are grand master, PTP client, and PTP-enabled
router acting as a Boundary clock.
Table 12-1 1588v2 PTP Support Matrix on a Cisco ASR1000 platform
Platform/PTP Clock mode
Ordinary
Clock
Boundary
Clock
Transparent
Clock Hybrid Clock
ASR1002X Yes Yes No No