Re: [tkined] unknown asn1 type 0x15

Juergen Schoenwaelder (schoenw@ibr.cs.tu-bs.de)
Thu, 16 Apr 1998 10:57:52 +0200

>>>>> Matthias Geining writes:

Matthias> I try to build a small scotty agent for Linux and Irix
Matthias> 6.2. I use scotty 2.1.7 and 2.1.8 with tcl/tk 7.6/4.2.

Matthias> I get an error when I try to get atNetAddress
Matthias> (1.3.6.1.2.1.3.1.1.3). It seams for me that there is not a
Matthias> big difference between atTable mib and ipNetToMediaTable
Matthias> mib. Therefore I write the same value to atNetAddress and
Matthias> ipNetToMediaAddress (1.3.6.1.2.1.4.22.1.3). I can read
Matthias> ipNetToMediaTable without problems. But I get the error on
Matthias> the agent

Matthias> unknown asn1 type 0x15 (snmp send reply)

Matthias> by reading atTable. If I don't set atNetAddress instance I
Matthias> can read the atTable. So whats wrong?

The short answer is simple: Don't implement atTable. This table has
been deprecated in RFC 1213, which was published seven years ago.

The longer answer goes as this: The atTable uses the SMI data type
NetworkAddress, which was defined as an ASN.1 CHOICE with a single
option: IpAddress. This idea proved to be problematic and hence the
only table using NetworkAddress in MIB-2 got deprecated. (Newer MIBs
use the textual conventions to define new address types, which is much
more flexible because it always maps to an OCTET STRING for a protocol
point of view. The problem with this approach however is that you
usually need two objects in order to interpret an address.)

Scotty does not really support the NetworkAddress SMI data type and I
guess this is the cause of the error message you got. I am not sure
whether this is worth to be fixed because the usage of NetworkAddress
is problematic in itself. (Note that NetworkAddress has been removed
from SMIv2 anyway.)
Juergen

-- 
Juergen Schoenwaelder  schoenw@ibr.cs.tu-bs.de http://www.cs.tu-bs.de/~schoenw
Technical University Braunschweig, Dept. Operating Systems & Computer Networks
Bueltenweg 74/75, 38106 Braunschweig, Germany.        (Tel. +49 531 / 391 3283)
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