Juniper ACX1000 Configuration Manual page 300

ACX Series Universal Access Router Configuration Guide
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You can configure a maximum of four slave ports on a router. A slave port or logical
interface is defined as any slave-only port configured for IPv4 or Ethernet, or any
dynamic port configured for Ethernet.
You can configure up to 29 master ports on a router. A master port or logical interface
is defined as any master-only port configured for IPv4 or Ethernet, or any dynamic
port configured for Ethernet.
Any logical interface that you configure as a dynamic port is considered to be both
a slave port and a master port, even if it functions only as a slave port or a master
port in a network, when the total number of slave ports and master ports on a router
is computed.
In PTP over IPv4 deployment, it is necessary to configure certain basic settings on a
PTP master port before the PTP slave ports to connect to the master port. PTP over
Ethernet offers a plug-and-play service because any PTP client starts receiving packets
and can request delay-response packets from the master port after you configure an
interface to be a master.
PTP over Ethernet is compatible with Junos OS releases earlier than Release 12.3X51.
When you perform an upgrade to Release 12.3X51 and later from a previous release on
an ACX Series router, you can modify the slave and master ports previously configured
for IPv4 to enable PTP over Ethernet based on your network needs.
You cannot configure a fully redundant PTP ring using IP. A fully redundant PTP ring
is supported only when Ethernet encapsulation is used.
Configuration of dynamic ports in conjunction with Synchronous Ethernet to enable
hybrid mode is not supported.
Multiple PTP timing domains are not supported for PTP over Ethernet, similar to PTP
over IPv4. Although a single node can contain interfaces configured for PTP over IPv4
and PTP over Ethernet, both of these interfaces must be part of the same PTP domain.
SONET/SDH networks define the ability to configure a local priority to a synchronization
source in the ITU G.781 standard. Addition of such locally configured priorities to PTP
sources to influence BMCA to determine a particular path for PTP packets is not
supported.
Although you can configure a slave port to use either IP or Ethernet simultaneously, a
single slave port is selected based on the announce messages it receives from the
master port and the PTP event packets are exchanged only with a single master port.
The IPv4 unicast implementation of PTP enables you to limit the number of slave ports
that can be supported simultaneously in the system. With multicast Ethernet-based
implementation, in which the master port is not provisioned with the slave port
information, the master port cannot limit the number of slave ports that it services.
This control must be exercised with proper networking planning and design.
PTP over Ethernet on ACX Series Routers Overview on page 238
Configuring PTP Multicast Master and Slave Ports for Ethernet Encapsulation on
page 274
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