Cisco Systems 1000 Series Manual De Usuario

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.

 

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 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.

The three key components of a PTP-enabled data network are grand master, PTP client, and PTP-enabled 
router acting as a Boundary clock. 

ASR1002X

Yes

Yes

No

No