Hi James,
>First, technically speaking, there are NO traps in SNMP V2, because SNMP V2
>does
>not recognize the trap designation (SNMP type a4) as supported.
SNMPv2c includes traps. It does not include v1 trap PDUs...which have
special formatting elements different from all other PDU types)...SNMPv2c
normalized the trap PDU to have the same format as all other PDU types,
and gave it a new PDU type code (a7). RFC 1908 gave initial info re how
to map between v1 and v2c traps; RFC 2089 later elaborated on that; and
now SNMPv3 provides the mapping in the "Coexistence" RFC (which I think
will be #2576 when it's foramlly publsihed as an RFC...it has already bene
approved as such by the IESG).
>SNMP V2 hatched a concept called "notifications" and another called
>"reports" which were meant to replace traps.
"Notifications" is simply a classifier for SNMPv2c traps and informs.
Informs are identical to traps in all respects except that the receiver
of an inform PDU must issue a response back to sender which simply
lets the sender know that the inform was received (not necessarily
acted on).
Reports are a new type of PDU that were defined with SNMPv2c but not
used until SNMPv3. They are intended to be "engine-to-engine"
signals and are not (typically) exposed to the higher layer apps.
>But no vendors, so far as I know, went along with this
>and thus traps are alive and well today.
Many vendors support SNMPv2c, including traps and informs.
>Second, trapd does have code to recognize when an agent says it is using SNMP
>V2
>as opposed to V1, but there should be no difference in the varbind structure.
>They are still "type-length-value" with the encoding done by the same Basic
>Encoding Rules of ASN.1.
That's partly correct...yes, varbinds and varbindlists have the
same structure and encoding rules in SNMPv1/v2c/v3. However, as part
of the normalization of the trap PDU format in SNMPv2c, some of the
special fields from the SNMPv1 trap PDU were moved to varbinds in
the varbindlist of the SNMPv2c trap PDU. When mapping a v1 trap to a
v2c trap, certain aspects of the positioning/ordering of varbinds
in the v2c varvbindlist are mandated by the standards (see specs
cited above). NetView would have to make the correct mappings
(and I certainly have no reason to think it does not!).
Cordially,
BobN
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