Lab 7 9.1 RMON Delta vs. Absolute

I just don't understand the difference between delta and absolute thresholds in RMON.  I know this is an often discussed topic, and it's given me a lot of trouble in labs and the real world.  Lab 7 task 9.1 says to configure RMON trap when ifEntry.11 from BB2 exceeds 15000.  Now in my mind that is a variable.  15000 = X.  In this case X has an absolute value that we are looking for.  Why then is this supposed to be delta in the config?  I thought delta was for measuring against a previous threshold.  Is it delta because we are also looking for a bottom threshold of 5000?  Or is it supposed to be delta based on the type of MIB?  If it is, how can we know what to configure when?  I am sure things like CPU utilization reaching 80% for example are an absolute threshold... but interface mibs give me fits... I just can't seem to figure it out... any help?

 

Thanks in advance for the help!  i am attempting SP lab for the 3rd time on May 4th!   Hopefully third times a charm!   These tests are not as well written and straight forward as the R&S.  But it's still fun... to a point :).

Comments

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    You have to look at what it is you are actually looking at.



    So let's say it was CPU Utilization (obviously not for 15,000 but we'll
    pretend).  Whatever value you pick like 80% will be an absolute value. 
    You can have it occur more than once and you want to know each time it
    happens.



    Now let's take something like packet count (or byte count/octets).  The
    number 15,000 will ONLY occur once.  Or at least once per 4.2 billion
    octets since that's a 32-bit number that rolls over.  So that makes no
    sense to measure as an absolutely value.  15,000 may be too much too,
    but it depends on how often you are measuring and how much traffic you
    EXPECT to have on that line!  Every 10 seconds on a 128K line may be an
    indication of something bad about to happen.



    So you have to take your measurement in context to really understand
    the absolute versus delta measurements.



    Good luck on your exam!  I hope I've helped a bit!






     



    Scott Morris, CCIEx4
    (R&S/ISP-Dial/Security/Service Provider) #4713,

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    apollogold wrote:

    I just don't understand the difference between delta and absolute
    thresholds in RMON.  I know this is an often discussed topic, and it's
    given me a lot of trouble in labs and the real world.  Lab 7 task 9.1
    says to configure RMON trap when ifEntry.11 from BB2 exceeds 15000. 
    Now in my mind that is a variable.  15000 = X.  In this case X has an
    absolute value that we are looking for.  Why then is this supposed to
    be delta in the config?  I thought delta was for measuring against a
    previous threshold.  Is it delta because we are also looking for a
    bottom threshold of 5000?  Or is it supposed to be delta based on the
    type of MIB?  If it is, how can we know what to configure when?  I am
    sure things like CPU utilization reaching 80% for example are an
    absolute threshold... but interface mibs give me fits... I just can't
    seem to figure it out... any help?

     

    Thanks in advance for the help!  i am attempting SP lab for the
    3rd time on May 4th!   Hopefully third times a charm!   These tests are
    not as well written and straight forward as the R&S.  But it's
    still fun... to a point :).







    Internetwork Expert - The Industry Leader in CCIE Preparation

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