System Management
7450 ESS OS Basic System Configuration Guide Page 247
In addition, performance is also improved by the removal of any PDV caused by internal queuing
within the boundary clock or slave clock. This is accomplished with hardware that is capable of
detecting and time stamping the IEEE 1588v2 packets at the Ethernet interface. This capability is
referred to as port-based time stamping.
NOTE: Support for port-based time stamping will be added to hardware modules over time.
Consult the latest release notes for a list of 7450 ESS modules capable of supporting port-based
time stamping of IEEE 1588v2 messages.
Port Based Timestamping of PTP Messages
For ultimate performance, the 1588 packets should be timestamped at the ingress and egress of the
7750 SR. This then avoids any possible PDV that might be introduced between the port and the
CPM. This capability to timestamp in the interface hardware is provided on a subset of the IMM
and MDA assemblies of the 7750 SR. Refer to the release descriptions for the complete list.
In order for this to operate, the CPM, IOM, IMM, and MDAs must be running the firmware that
supports the capability. The CPM firmware upgrade occurs automatically when the CPM card
software is updated. Since upgrading of IOM, IMM, and MDA firmware is service impacting, this
upgrade is not performed automatically on a soft reset of the MDA. The IOM/IMM firmware is
upgraded when the IOM/IMM card is hard reset. The MDA firmware is programmed during
system initialization, when the MDA is inserted, or when the MDA is hard reset via a clear mda
or clear card command. However, when an MDA is soft reset via either a clear card soft
command or during a major ISSU, the MDA firmware is not updated.
PTP Capabilities
PTP messages are supported via IPv4 unicast with a fixed IP header size. Table 32 describes the
support message rates for slave and master states. The ordinary clock can be either in the slave or
master state.
Table 27: Support Message Rates for Slave and Master Clock States
Support Message Slave Clock Master Clock
Request Rate Grant Rate
Min Max
Announce 1 packet every 2
seconds
1 packets every 2
seconds
1 packets every 2
seconds
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