PTP messages are supported via IPv4 unicast with a fixed IP header size or via IPv6.
PTP messaging is supported on network interfaces. If a node loopback address is used as the source interface for 1588 packets, the packets can ingress any network IP interface on the router. If the source interface is associated with a physical port, packets must be sent to the interface on that port.
PTP messaging is also supported on IES interfaces for access ports.
The 7705 SAR can also forward IPv4-encapsulated PTP messages over BGP-LU routes for frequency synchronization. The following profiles are supported for these messages: ieee1588-2008, itu-telecom-freq, and g8275dot2-2016.
Table: Rates for IP-Encapsulated PTP Messages describes the supported message rates for slave and master states for IP-encapsulated PTP traffic, based on the profile configured. The ordinary clock can be either in the slave or master state. The boundary clock can be in both of these states.
ieee1588-2008 |
itu-telecom-freq |
g8275dot1-2014 g8275dot2-2016 |
||
|---|---|---|---|---|
Announce |
Minimum rate |
1 per 16 seconds |
1 per 16 seconds |
1 per 16 seconds |
Maximum rate |
8 per second |
8 per second |
8 per second |
|
Default rate |
1 per 2 seconds |
1 per 2 seconds |
8 per second |
|
Sync and Delay |
Minimum rate1 |
64 per second |
64 per second |
16 per second |
Maximum rate |
128 per second |
128 per second |
128 per second |
|
Default rate |
64 per second |
64 per second |
16 per second |
|
See Table: Rates for Ethernet-Encapsulated PTP Messages for the supported message rates for Ethernet-encapsulated PTP traffic.
State and statistics data for each master clock are available to assist in the detection of failures or unusual situations.
The PTP algorithm is able to recover the clock using both the upstream and downstream directions in both ordinary slave and boundary clock modes. The ability to perform bidirectional recovery improves the performance of networks where the upstream and downstream load is not symmetrical.
The Bell Labs algorithm looks at the PTP packet exchange in both directions between the master and slave. There can be more packet delay variation in one direction if there is a high utilization rate or congestion in that direction. The algorithm assesses the stability and reliability of the packet exchange in each direction and assigns weight values based on the results. The system gives preference to frequency synchronization from the direction with a higher weight value. The weight values change dynamically and can be viewed with detailed PTP show commands.