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<div class="heading">NMIS Documentation</div>
<table>
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<td width="33%">Last updated 21 June 2001</td>
<td width="33%">
<p align="center"><a href="http://www.sins.com.au/nmis/nmis-doc.html">Online
Version</a></p>
</td>
<td width="33%">
<p align="center"><a href="http://www.sins.com.au/nmis/">NMIS Home Page</a></p>
</td>
</tr>
<tr>
<td width="50%" colspan="3">
<ul>
<li><a href="http://www.sins.com.au/sins/nmis/">NMIS Home Page</a> </li>
<li><a href="#Introduction">Introduction</a></li>
<li><a href="#Concepts">Concepts</a></li>
<li><a href="#RolesAndGroups">Roles and Groups</a></li>
<li><a href="#Health">Health</a></li>
<li><a href="#Events">Events</a></li>
<li><a href="#Thresholds">Thresholds</a></li>
<li><a href="#Updates">Updates</a></li>
<li><a href="#Interfaces">Interfaces</a></li>
</ul>
</td>
</tr>
<tr>
<td width="100%" colspan="3"><b><a name="Introduction">Introduction</a></b><p>
NMIS stands for Network Management Information System. It is a Network
Management System which performs multiple functions from the OSI Network Management
Functional Areas, those being, Performance, Configuration, Fault. A
primary function of NMIS is to make information about your network
available quickly and instantly. Some of this network is provided
"raw" other information is provided in a related manner.</p>
<p>It started as a SNMP polling and statistics viewer front-end to Tobi
Oetiker's <a href="http://ee-staff.ethz.ch/~oetiker/webtools/rrdtool/">RRDTool</a>. <a
href="http://ee-staff.ethz.ch/~oetiker/webtools/rrdtool/">RRDTool</a> replaces <a
href="http://ee-staff.ethz.ch/~oetiker/webtools/mrtg/mrtg.html">MRTG</a> but doesn't
include a front end and backend to handle SNMP polling and display resulting web pages
etc. The original NMIS evolved quite rapidly to meet demands of production
environments. </p>
<p> The backend, polling engine, uses SNMP to collect interface and health
statistics for Cisco Routers, certain Cisco Catalyst Switches and Generic SNMP devices
every 5 minutes. The collected statistics are stored in RRD's (Round Robin Databases)
and ensures that devices are up, issues alerts, etc. The
front end accesses the information stored in the RRD's and displays statistics the
resulting graphs, reports, etc. </p>
<p>Both the front and back ends are highly extensible and features are
easy to add as the structure is learnt. For example the backend was just collecting
interface statistics every poll cycle, it was easy to add collection of health (cpu,
memory, buffer, etc) and response time, availability.</p>
<p>NMIS uses a backend to collect data and maintain the information about
the data. It relies on RRD for databases, additional tables are text
based configuration information. The frontend is independant, it just
reads information from the RRD's and text tables and displays the
information. Simple.</p>
<p>It is intended that NMIS be low maintenance once it is running, it should
just go and go. More work needs to be done on this but I think it
going well so far.</p>
</td>
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<tr>
<td width="100%" colspan="3"><b><a name="Concepts">Concepts</a></b>
<p>The basic concept is that NMIS collects interface, CPU, Memory, buffer
and packet statistics from Cisco Routers and Switches, it is also capable
of supporting generic SNMP MIB 2 collection. Getting slightly
deeper, NMIS pings a device every poll cycle verifies that it is
"up", this is called "reachability", it holds this in
memory. </p>
<p>If no system information is available for the device it must be a new
device so perform a capabilities discovery on the device, this is the
subroutine getNodeInfo. Otherwise load the cached system information
with the loadSystemFile then run the updateUptime subroutine which gets
sysObjectID, sysUpTime and ifNumber, NMIS compares this with the cached
information to see if the same number of interfaces are present, that the
uptime has increased and that the sysObjectID is the same. </p>
<p>If the number of interfaces has changed run the createInterfaceFile
subroutine to update this information. (This should send an
configuration change event.)</p>
<p>If the sysObjectID has changed run the getNodeInfo subroutine. (This
should send an configuration change event.)</p>
<p>If the sysUptime is less then the cached information sysObjectID has
changed run the getNodeInfo subroutine. (This should send an node reload
event.)</p>
<p>The runHealth subroutine is run, this collects CPU, Memory, buffers,
etc, whatever is deemed necessary for that device type and stick it all in
an RRD. </p>
<p>Then the runInterfaces subroutine is run, it loads the cached interface
information, if none exists it creates it with createInterfaceFile.
Then for each interface it collects ifDescr, ifOperStatus, ifInOctets and
ifOutOctets. If the ifDescr is different, the cached interface
information must be out of date (this is how shifting ifIndex is handled)
create it again with createInterfaceFile. If the ifOperStatus shows
down when the interface is supposed to be up, raise an event.
Otherwise store ifOperStatus, ifInOctets and ifOutOctets in an RRD, adding
ifOperStatus to the total interface availability of the device.</p>
<p>After the interfaces are complete, calculate the response time for the
device with another ping and store some health metrics in another RRD, we
store the reachability of the device, the interface availability of the
device, the responsetime and create a health metric from a simple
algorithm which weights various collections and makes up a metric to
indicate the overall health of that device, more on this in the <a href="#Health">health</a>
section.</td>
</tr>
<tr>
<td width="100%" colspan="3"><b><a name="RolesAndGroups">Roles and Groups</a></b>
<p>The ability exists to put nodes into two types of groups, the first
group is a role which is core, distribution and access, the second group
is used to group devices together for reports, and general
information. It is logical hat the second group be something like
the building name or city/suburb of the device as this helps identify
problem areas.<p>Roles play an important part in NMIS, they allow things
to be weighted for events and various other functions. The concept
of weighting according to role is simple, if it is a core device then it
is important and should be treated as such, if it an access device then it
is less important. The idea is to try and remove the noise, ie all
events coming in at critical and which ones really are.</td>
</tr>
<tr>
<td width="100%" colspan="3"><b><a name="Health">Health</a></b>
<p>The following statistics are considered part of the health of the
device:</p>
<ul>
<li>Reachability - is it up or not; </li>
<li>Availability - interface availability of all interface which are
supposed to be up; </li>
<li>Response Time; </li>
<li>CPU; </li>
<li>Memory; </li>
</ul>
<p>All of these metrics are weighted and a health metric is created.
This metric when compared over time should always indicate the relative
health of the device. Interfaces which aren't being used should be
shutdown so that the health metric remains realistic. The exact
calculations can be seen in the runReachability subroutine.</td>
</tr>
<tr>
<td width="100%" colspan="3"><b><a name="Events">Events</a></b>
<ul>
<li>Escalation</li>
<li>Events based on device role</li>
<li>Stateful</li>
</ul>
</td>
</tr>
<tr>
<td width="100%" colspan="3"><b><a name="Thresholds">Thresholds</a></b><p>The thresholds
routine runs whenever you like, it process the collected statistics in the
RRDs and compares the numbers to stored thresholds and if exceeded raises
an event for that device. The thresholds use the device role to
weight the events.</td>
</tr>
<tr>
<td width="100%" colspan="3"><b><a name="Updates">Updates</a></b><p>Updates ensures that
all the cached system and interface information is kept up to date.
If the network is constantly changing then it should be run frequently,
otherwise it could be run less frequently.</td>
</tr>
<tr>
<td width="100%" colspan="3"><b><a name="Interfaces">Interfaces</a></b>
<p>Interfaces which aren't in use should be shutdown (admin down) so that
NMIS doesn't think it is supposed to manage them. A simple lookup is
done on interface types to determine if NMIS should collect statistics on
them. This is done during the createInterfaceFile subroutine.</td>
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distrib
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Mandriva
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2009.1
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x86_64
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media
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contrib-release
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by-pkgid
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14e7762649c6c85d29d87b731da4bd26
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39
