Network Management

Week 8, Mar 21
LT-412, Mon 4:15-6:45 pm

Java

We will use the Drexel University Java SNMP package.

snmpget.java

This is a mini-version of the snmpget command; it retrieves a single OID. It assumes localhost.
Review the code:

Create the SNMPv1CommunicationInterface object
Create the OID for which we are looking
getMIBEntry (this performs the actual request)
extract the value:

newVars is the VarBindList returned
pair is the first component of newVars, an (OID,value) pair
snmpValue is the second component of pair

downcast to correct actual type

Note that although the documentation states that an OID is to convert to an int[], this in fact does not work; it must be long[].

Compiling and running:
    CLASSPATH=".:snmp.jar:$CLASSPATH"
    export CLASSPATH
    javac snmpget.java
    java snmpget arg

Demo on system group 1.3.6.1.2.1.1.x.0, 1.3.6.1.2.1.2.2.1.6.2

snmpgetnext.java
1.3.6.1.2.1.4.20 (should be an IP address)

tableget1.java

Demo of table retrieval. Here we use retrieveMIBTable, rather than getMIBEntry. The only difference is that we now retrieve a rather long SNMPVarBindList rather than one of length 1. Note makeArrayList(), not actually used.

What would you have to do to retrieve one row of this table?
What would you have to do to retrieve row i, column j?
What would you have to do to get a column? Assuming you did not know the dimensions of the table?
What would you have to do to get all the OID index values?

tableget2.java

Here I convert from SNMPVarBindList to ArrayList<SNMPSequence>. Also, printing is deferred until the end, and there is a printValue method that does some casting.

Some NMS products:

    OpenNMS:
    GroundWork
    Nagios

    lots of commercial ones

    Why open source? To get people to write app-specific modules!

Centralized v Distributed configurations
    Two basic strategies:

one NMS, queries all agents
intermediate agents querying subagents, collating results, reporting to master NMS

The latter can be leveraged into multi-layer management structures

Inter-AS routing: BGP
        complex administrative choices
        transit or no transit?
        Accept routes from neighbors (input selection)
        route selection?
        advertise chosen route to where? (output selection)
        Multi_exit_discriminator (MED)