Re: lexicographic successor confusion

2009/2/10 Ragesh V <[email protected]>:
> Following are our MIB table entries.
>
> X.X.X.X.X.X.22.1.1
> X.X.X.X.X.X.22.1.1.1
> X.X.X.X.X.X.22.1.1.1000
> X.X.X.X.X.X.22.1.1.1001

I presume you've got a MIB structure of the form:

    myTable ::=  ... { X X ... 22 }
    myEntry ::=  ... { X X ... 22 1 }
    myCol1  ::=  ... { X X ... 22 1 1 }

and three rows with index values 1, 1000 & 1001

So X.X.X.X.X.X.22.1.1 would be the OID of the myCol1
MIB object, and would never appear as the result of
a GETNEXT request.
  (Which is where the idea of "lexically next" OIDs
tends to crop up)


> X.X.X.X.X.X.30.1.1
> X.X.X.X.X.X.30.1.1.1

And this is presumably a different table.


> In the above table our understanding is that the lexicographic successor for
> an OID is the immediate child of that OID

No.
The lexicographic successor is the next OID in a linear ordering of all valid
instances.   Whether this is a child, or a sibling, or a completely unrelated
OID is not relevant.


> and the next OID in the MIB tree cannot be the successor.

Wrong.
The next OID in the MIB tree *will* be the successor, if there are no
valid instances in the child subtree.



> For example, the OID "X.X.X.X.X.X.29.1.1" following are the lexicographical
> successors

> X.X.X.X.X.X.22.1.1.1

This comes *before* ....29.1.1 so cannot be a successor of it.


The successor of X.X.X.22.1.1 will be  X.X.X.22.1.1
The successor of X.X.X.22.1.1.1 will be  X.X.X.22.1.1000
The successor of X.X.X.22.1.1.1000 will be  X.X.X.22.1.1001
The successor of X.X.X.22.1.1.1001 will be  X.X.X.30.1.1.1

   (assuming that X.X.X.30.1.1 is the OID of the object itself, not an instance)



> The OID "X.X.X.X.X.X.30.1.1" cannot be the lexicographic successor for the
> "X.X.X.X.X.X.29.1.1".

Wrong(-ish)
X.X.X.30.1.1.1  *will* be the successor to X.X.X.29.1.1
  (even though X.X.X.29.1.1 is not a valid MIB object in the agent)

> Is our understanding correct or not??

Not

Dave

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