Precise time in traps
Christopher Nelson
traps to a third system, should I expect that the times in the traps
when the server sees them are fairly accurate and coordinated and
allows me to tell which trapped event happened first? Or is the time
in the traps SNMPd uptime or something that won't be adjusted as PTP
updates the system clock?
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Dave Shield
> If I have two systems running PTP (precision time protocol) which send
> traps to a third system, should I expect that the times in the traps
> when the server sees them are fairly accurate and coordinated and
> allows me to tell which trapped event happened first? Or is the time
> in the traps SNMPd uptime or something that won't be adjusted as PTP
> updates the system clock?
The sysUpTime value in a notification is the time that the SNMP
agent has been running. This will not be coordinated between
separate systems. (This value may also be affected by tweaks
to the system clock).
So no - this timestamp is not going to be useful in ordering events.
You haven't said anything about the payload of these traps.
If they include timestamp varbinds provided by the PTP module,
then it's quite possible that the values will be more accurate.
But the standard SNMP trap information won't really help you here.
Dave
Christopher Nelson
>> traps to a third system, should I expect that the times in the traps
>> when the server sees them are fairly accurate and coordinated and
>> allows me to tell which trapped event happened first? Or is the time
>> in the traps SNMPd uptime or something that won't be adjusted as PTP
>> updates the system clock?
>
> The sysUpTime value in a notification is the time that the SNMP
> agent has been running. This will not be coordinated between
> separate systems. (This value may also be affected by tweaks
> to the system clock).
> So no - this timestamp is not going to be useful in ordering events.
>
> You haven't said anything about the payload of these traps.
> If they include timestamp varbinds provided by the PTP module,
> then it's quite possible that the values will be more accurate.
> But the standard SNMP trap information won't really help you here.
No doubt I could create a PTP-based trap but I was thinking of things
like cold start and link up. Sounds like I don't gain anything in
trap analysis by having highly-coordinated clocks. Thanks.
Mike Ayers
> Sent: Wednesday, December 16, 2009 4:48 AM
> No doubt I could create a PTP-based trap but I was thinking of things
> like cold start and link up. Sounds like I don't gain anything in
> trap analysis by having highly-coordinated clocks. Thanks.
Hmmm... if you can find an object for the system clock time, then you could perform gets on sysUpTime and sysClockTime in the same packet. A little jitter interpolation and you could quickly get very close to the coordinated time value of received traps.
HTH,
Mike