From: Guyler, Rik (rguyler@shp-dayton.org)
Date: Wed Oct 03 2007 - 17:12:04 ART
Andy, the numbers are absolute but they are used as a threshold in reference
to a given slice of time. In this case delta is correct because you need to
monitor the amount of change within that time slice. Absolute would monitor
the change from the very beginning.
Here's an example:
If your number started out at zero and climbed to 100,000 but never climbed
more than 10,000 per minute then the absolute number of 100,000 means
nothing to this scenario. Now, if at the 10 minute mark you jump from
100,000 to 150,000 in 30 seconds, then the delta from the 10 minute mark to
the 11 minute mark satisfies the condition and triggers the alarm or
whatever.
If the requirements read that you need to trigger the alarm when the total
number of errors reaches 100,000 no matter how long it takes, then the
absolute value would be correct.
Delta is simply stating that you have to have a certain number of events
during a certain slice of time. In other words, in your scenario, at the
end of each 60 second time slice the delta counter gets reset back to zero
even though the absolute counter continues to climb.
Rik
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Andy
Cole
Sent: Wednesday, October 03, 2007 2:55 PM
To: Cisco certification
Subject: RMON Absolute or Delta ?
When configuring RMON you need to choose between Absolute or Delta. I pick
the wrong one about half the time, (might be better off just flipping a
coin).
The way I remember which does what:
Delta = Difference
Absolute = Fixed number
Task:
The network administrator has requested that R1 log an event when the
interface input octets value reaches 45000 per minute and when the value
falls back below 35000 per minute.
In my mind these are absolute numbers (45000 & 35000) But the solution
calls for Delta.
I need help understanding when to use Absolute and when to use Delta.
Andy
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