Subject: Sub Agent Processing of AgentX GetNext Response

From: "Ashish Hanwadikar" <[email-masked]>
Date: Fri, 31 Jul 1998 19:29:15 +0530

Hi all,
	While going through the AgentX RFC we noticed one ambiguity:

"Section	7.2.2.2.  Subagent Processing of the agentx-GetNext-PDU
   Upon the subagent's receipt of an agentx-GetNext-PDU, each
   SearchRange in the request is processed as follows:
   (1) The subagent searches for a variable within the
       lexicographically ordered list of variable names for all
       variables it instantiates (without regard to registration of
       regions) within the indicated context and session, for which the
       following are all true:"

	Suppose master agent sends AgentX GetNext request to a subagent (Sub Agent
#1) with a SearchRange (falling under a target MIB Region #1). The sub agent
responds with a oid and its value falling under a different MIB Region
(lexicographically after MIB Region #1). Lets call these region as MIB
Region #2. Now suppose another sub agent had registered an MIB Region #3.
The lexicographical relationship is
	MIB Region #1 < #3 < #2
	That means, if the SearchRange doesn't fall within MIB Region #1, then
ideally target sub agent should return endOfMIBView. The Master Agent will
find lexicographically next region, i.e. MIB Region #3 (by subagent #2) and
resend the request to sub agent #2.
	If first sub agent returns the oid and value from MIB Region #2 (as he has
to search through a list of lexicographically ordered list of instantiated
variables without regard to registration of region), then the SNMP Response
for SNMP GetNext will be wrong.
	Either this is a error or it is not clear what is meant by "without regard
to registration of MIB region". Please clarify.
	Also, in the section "7.2.4.3.  Processing of Responses to
agentx-GetNext-PDU and agentx-GetBulk-PDU ", the Master Agent never checks
whether for each oid in the VarBind the response returned by a sub agent is
valid or not. I think the master agent should check whether, for the oid in
the varbind, the response returned by the sub agent is falling within the
target MIB Region (which he determined while preparing the AgentX GetNext
PDU for that particular sub agent).
	Thanks.
With regards,
Ashish K Hanwadikar
Senior Software Engineer,
Wipro Infotech, Technology Solutions,
Bangalore
INDIA

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From: Mike Daniele <[email-masked]>
Date: Fri, 31 Jul 98 12:58:03 -0400

Hi Ashish,

>PDU for that particular sub agent).

7.2.1 states

    1) Honoring the registry

      Because AgentX supports overlapping registrations, it is possible
      for the master agent to obtain a value for a requested varbind
      from within multiple registered MIB regions.

      The master agent must ensure that the value (or exception)
      actually returned in the SNMP response PDU is taken from the
      authoritative region (as defined in section 7.1.5.1).

I think this "blanket rule" covers your concerns.

Note that the master agent may use the ending oid of the
searchrange to "scope" the instances the subagent may return,
as described in 2) of section 7.2.1, and 7.2.2.2.

Does this make it clear?

Regards,
Mike