I am an engineer my the Air Traffic Control provider in New Zealand. We are looking at upgrading our remote control equipment. At remote sites we have radio and navigation equipment which typically have remote interfaces via floating relay contact outputs and opto-isolated inputs.

To many of these sites we now have LAN connections so a PLC interface at the remote site with a SNMP MIB browser at the central site seems an attractive solution. Devices such as the Omron CS1W-ETNO1 and Siemens CP343-1 IT support TCP/IP, FTP and SMTP, but not SNMP. I have asked Siemens and Omron if their PLCs are likely to support SNMP in the future, but have not got a reply.

Does anyone know if a simple application could be written on such devices that would support SNMP?

 

Look at the TECLA product line at www.oldi.com. An embedded PC, Programmable Data Processor which can interface to a variety of sensors, I/O, industrial controls, popular automation networks, and enterprise
information systems.

Best Regards,

Ray W. Valentine
Sales Engineer
Online Development Inc.
Ph.: 865-251-5222
Email: [email protected]

 

Check out SIXNET's IPm controllers and RTUs which are comparable replacements for any PLC. They support SNMP in addition to TCP/IP, FTP, Telnet, PPP, Modbus, web server and much more.

For details please go to:
http://www.sixnetio.com/html_files/oems/ipm_addons.htm#snmp

 

You didn't say if you wanted SNMP just for network stats, or as an actual application interface. For network stats, just use managed hub/switches. For a data/app protocol, using something Modbus or HostLink or ??? will be easier that SNMP.

Easy to add? Not likely - unless it's some special add-on card for custom IP-stack development. Parsing the OID (those chains X.X.X.X.X.X.X.X) is a fairly mechanical but not trivial problem. You'd need a fairly complete support library to handle these and walking and the nodes/leaf data types. Plus if you wanted MIB II stuff, likely you'll have NO access to any of that data in the RTOS.

I know a few PLC companies WITH SNMP just turned them off since CERT declared most default SNMP as "security risks". In fact, many people say SNMP stands for "Security's Not *MY* Problem". There is SNMPv3 (with fairly good security) but few devices support it.

Problems with SNMP:
1) most people just do the insecure v1 or v2

2) most PLC likely just support MIB II, which is just the Ethernet stats. Since a managed hub/swicth ALSO keeps these, you'd get very little extra value moving them to the PLC.

3) most SNMP implement the various counters in a vendor-specific way. There's one infamous "test" from the mid-90's that ran a know script of bad Enet/IP packets past 20 commercial bridges and NONE of them gave the exact result - some recorded NO errors at all so the "counters" where just dummy values always zero.

- LynnL

 

iSNMP software contains a "basic" GUI that will gather your SNMP Mib data.

find it at http://www.coisoftware.com/

 

Have a look at www.obermeier-software.de or email at [email protected] for further details. SNMP is quite a good idea for monitoring your ATC equipment. As i know even some modern radio and radar systems (i.e: Rohde & Schwarz) have SNMP "onboard". We have done two projects with a european ATC provider and SNMP was a "key-feature" there. Depending on your detailed requirements there are several ways for integrating various "external" signals (i.e. relay contacts) via SNMP. So you can build up a centralized monitoring system for monitoring all of your "business-critical" assets like your ATC equipment AND your LAN which is connecting the remote sites.

Greetings
Stefan