Basic System Configuration Guide System Management
Edition: 01 3HE 11010 AAAC TQZZA 249
6.4.6.11 PTP Clock Redundancy
Each PTP slave clock can be configured to receive timing from up to two PTP master
clocks. If two PTP master clocks are configured, and if communication to the best
master is lost or if the BMCA determines that the other PTP master clock is better,
then the PTP slave clock switches to the other PTP master clock.
For a redundant or simple CSM configuration on the 7705 SAR-8 and 7705 SAR-18,
a maximum of two PTP slave clocks can be configured as the source of reference
(ref1 and ref2) to the SSU. If a failure occurs between the PTP slave clock and the
master clock, the SSU detects that ref1 or ref2 is unavailable and automatically
switches to the other reference source. This switching provides PTP hot redundancy
for hardware failures (on the 8-port Ethernet Adapter card, version 2, 6-port Ethernet
10Gbps Adapter card, 8-port Gigabit Ethernet Adapter card, 10-port 1GigE/1-port
10GigE X-Adapter card, or Packet Microwave Adapter card) or port or facility failures
(SFP or cut fiber). If a loopback address is used, PTP packets may arrive on any
router network interface and the PTP clock will remain up.
The 7705 SAR-M (all variants), 7705 SAR-H, 7705 SAR-Hc, 7705 SAR-A (both
variants), 7705 SAR-Ax, 7705 SAR-W, 7705 SAR-Wx (all variants), and
7705 SAR-X support only one PTP slave clock. This slave clock can be configured
as the source of reference (ref1 or ref2) to the SSU.
6.4.6.12 PTP Ethernet Capabilities
The 7705 SAR can be configured to transmit and receive PTP messages over a port
that uses Ethernet encapsulation. The encapsulation type can be null, dot1q, or qinq.
Ethernet-encapsulated PTP messages are processed on the node CSM or CSM
functional block, and they are supported on ordinary slave, ordinary master, or
boundary clocks for either frequency or time of day/phase recovery. The
7705 SAR-Ax can also support a grand master clock. The 7705 SAR-H,
7705 SAR-Wx, 7705 SAR-8 (CSMv2 only), and 7705 SAR-18 can also support a
grand master clock when equipped to support GNSS. A PTP clock using Ethernet
encapsulation can support up to 50 external peer clocks.
All platforms and cards that support PTP functionality support Ethernet-encapsulated
PTP messages, except for the 8-port Ethernet Adapter card v2, and the 2-port
10GigE (Ethernet) Adapter card/module. See Table 25 and Table 26 for a complete
list of supported platforms and cards.
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