Re: Question Concerning Lexicographical Search

[Olivier Miakinen <[e-mail]>]

Kai Mao wrote:
> 
> Hello!
> 
>         I have a general SNMP implementation question.
> 
>         I have a question concerning the OID table used by SNMP's
> lexicographical search for GetNext requests.  How is the GetNext OID
> calculated without using a table?  It seems silly to maintain an ordered
> OID table of all the objects and instances for the GetNext requests.
> Since most SNMP agents utilize method routines for data retrieval, why
> should the SNMP agent have to maintain the OID table with information on
> instances?  Shouldn't the agent be isolated from information concerning
> instances?  But I just don't see how the GetNext can be performed
> without maintaining the OID table.

There is no need to maintain a lexicographically ordered table of
all instances. In some cases it is even impossible (for example the
tcpConnTable and the udpTable in MIB-II).

What you need is, when you receive a GetNext request, to read the
instances once (in any order) and to retain the smallest instance
that is greater than the one asked in the request. It is not so
hard to do.

Olivier.

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