Conference 7.286::fddi

966.0. "DECconcentrator 500 SNMP 'ifInUnknownProtos' ???" by HADRES::KRAUSE (European NewProductEngineer for MCC) Tue May 25 1993 05:57

*** DECconcentrator 500 V3.1 SNMP Agent ***

I'd like to know the exact meaning of the SNMP variable
"ifInUnknownProtos" as supplied by the DECconcentrator 500 under 
"interface 1". This variable is part of MIB II but the description there 
is fairly general:

          Syntax:
               Counter

          Definition:
               The number of packets received via the interface which
               were discarded because of an unknown or unsupported
               protocol.

But what does this mean in the context of a Dc500 ?

Background: This variable counts up quickly. The Performance Analyzer
module of DECmcc counts "ifInUnknownProtos" as errors which results in 
an Inbound Error Packet Percentage of e.g. 85%. The network itself does 
not show any error symptoms. Querying the Dc500 with MCC's Concentrator 
AM (RBMS protocol) does not show any error counts, nor does it show any 
value in the range given by "ifInUnknownProtos".

I assume that "ifInUnknownProtos" does not count any errors, but a
certain type of good frames. But which ?  An explanation would surely
please our customer - pointers to documentation are welcome. To solve
the statistics problem this value should be moved to another variable,
e.g. into the DEC ELAN MIB. The MIB II description clearly implies an
error condition, so I think that the MCC PA correctly puts it in the
error statistics. 

Regrads from Munich,

*Robert

(CSC engineer)