7210 SAS-MXP, R6, R12, S, SX, T BASIC SYSTEM
CONFIGURATION GUIDE RELEASE 22.9.R1
System management
If the internal PTP process is used as a time source for System Time and OAM, it must be specified as a
server for NTP. If PTP is specified, the prefer parameter must also be specified. After PTP has established
a UTC traceable time from an external grandmaster source, that clock will always be the time source into
NTP, even if PTP goes into time holdover.
Note:
Use of the internal PTP time source for NTP promotes the internal NTP server to stratum 1 level.
This may impact the NTP network topology.
The following NTP elements are supported:
• server mode
In this mode, the node advertises the ability to act as a clock source for other network elements. By
default, the node will, by default, transmits NTP packets in NTP version 4 mode.
• authentication keys
These keys implement increased security support in carrier and other networks. Both DES and MD5
authentication are supported, as well as multiple keys.
• symmetric active mode
In this mode, the NTP is synchronized with a specific node that is considered more trustworthy or
accurate than other nodes carrying NTP in the system. This mode requires that a specific peer is set.
• broadcast
In this mode, the node receives or sends using a broadcast address.
• alert when NTP server is not available
When none of the configured servers are reachable on the node, the system reverts to manual
timekeeping and issues a critical alarm. When a server becomes available, a trap is issued indicating
that standard operation has resumed.
• NTP and SNTP
If both NTP and SNTP are enabled on the node, SNTP transitions to an operationally down state. If
NTP is removed from the configuration or shut down, SNTP resumes an operationally up state.
• gradual clock adjustment
Because several applications (such as Service Assurance Agent (SAA)) can use the clock, if a major
adjustment (128 ms or more) is needed, it is performed by programmatically stepping the clock. If a
minor (less than 128 ms) adjustment is needed, it is performed by either speeding up or slowing down
the clock.
• rate limit events and traps
To avoid the generation of excessive events and traps the NTP module rate limits the generation of
events and traps to three per second. At that point, a single trap is generated to indicate that event and
trap squashing is taking place.
6.1.2.3 SNTP time synchronization
To synchronize the system clock with outside time sources, the 7210 SAS devices include a Simple
Network Time Protocol (SNTP) client. As defined in RFC 2030, SNTP Version 4 is an adaptation of NTP.
SNTP typically provides time accuracy within 100 ms of the time source. SNTP can only receive the time
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