Need help getting a handle on SNMP [closed]

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I'm implementing some SNMP functionality into an application so I can query devices for some basic data like serial numbers, name, manufacture, etc. I've had some reasonable success getting some rudimentary SNMP calls to work. I was mostly helped along by some test code I got off of www.codeproject.com. There were some bugs in it that I was able to debug using the help of this web page http://www.rane.com/note161.html. This web page laid out a nice actual example of a SNMP packet so I was able parse the packet myself.

The problem is though, this information is from a an Audio equipment manufacture LOL. So this is by no means a complete reference guide into SNMP. But it was pretty darn good and taught me alot about the protocol. I've looked all over to try and find anything that was as good as this to help me get a complete understanding of SNMP and have come up empty handed. Most resources seemed to be tilted to using third party SNMP solutions. I want something that says... "this byte means this, and that byte means that", because ultimately I have to parse these packets coming back from the devices. And unfortunately, they don't all look like the examples given from the Rane Coproration page. I've even tried looking over some RFCs, and my god my eyes glaze over after about 10 minutes of trying to find what I want. I mean how hard should it be to find a byte by byte description of such a well known protocol as SNMP?

Does anyone know were I can find some good information for SNMP that is on par with this? Maybe the information I need is indeed buried in some of the dozen of hundred page RFC documents, and someone can just show me where precisely in those documents the information I'm looking for exists.

Answer 1

The RFC references for SNMP seem a little abstract, because SNMP is actually built upon ASN.1 which defines a compact binary encoding of typed data. For the whole picture you have to dive into the ASN.1 standards too.

A good ASN.1 reference is A Layman's Guide to a Subset of ASN.1, BER, and DER, and the Wikipedia page on Basic Encoding Rules also has a good overview. Neither of these deal specifically with SNMP, but it should be enough to fit the pieces together.

Another reference that might be helpful is http://www.vijaymukhi.com/vmis/snmp.htm. It's written in a very casual style but might address some points missed elsewhere.

(You may have noticed that protocols with the word "Simple" in their name, usually aren't.)