1.6 The
Holy Grail of Discovery?
Network discovery is the proverbial "Holy Grail"
of network operations. Everyone dreams of perfection in network discovery, but few have
found it, and a perfect automated discovery solution for one person is not often the best
for another, who only wants certain conceptually selected devices. Many people observe
that all the time it takes to tune things to make the "perfect auto-discovery"
it would be just as fast to enter the IP addresses by hand for exactly the devices needed
to be monitored.Indeed, in our
experience, a simple user-defined, manually entered operations model has often proven to
be the shortest and fastest path to model exactly what the user needs/wants to model. This
problem of seeking the Holy Grail of Discovery, combined with pragmatic limitations of
perfection in discovery has led us to take a more hybrid approach.
We wanted to give the user the ability to do network
scans and add devices automatically, but had to deliver this in a very targeted manner so
that the software only searches designated discovery zones of the network. Additionally,
the software had to support the people who prefer to build their own models explicitly
through AutoNOC's interpreter or via the web GUI as there are quite a few network managers
who simply do not allow network discovery on their networks.
The result of these experiences is the current
implementation of discovery in AutoNOC. There are two components of it. The first
component is the Network object. This is the user designed object that specifies
targeted ranges in the network that AutoNOC should search within, including which tickets
should be used, etc. The second component is the background Network Crawler. The
network crawler scurries around in the operations model comparing the model to the real
network. If it detects any changes between the model and the network it will make them.
1.6.1 Targeted Discovery with the
Network Object
When a new user starts the software up, they will be
prompted with a dialog box that simplifies a default network object down to seed IP
addresses and the related community and agent names. This dialog pre-configures a default
starting Network Object.
Each Network Object has separate targeted
network zones, methods, rules, community names, etc. Everything needed to discover a
certain part of a network. The network objects periodically execute and scan their
designated target zones. They can add devices and also remove devices that are no longer
present.
The screenshot above shows the methods tab
of the network object.
1.6.2 Network Crawler
The Network Crawler is disabled by default. Once
enabled (it is enabled as a property of the Discovery service) the software will
periodically patrol the network model and search for differences between the model and the
actual network objects. If it finds differences between the real object and the model it
will modify the model to update it with the new changes.
Note that the software also makes use of a Discovery
Grace Period. The grace period determines how long a given difference must exist
prior to making the change to the model. This allows the software a window to detect, for
instance, down interfaces, prior to actually removing them from the model. The network
crawler runs as a background low-impact process. Devices that are currently being
controlled are identified by a star in the Design tab of the GUI. The software
will crawl one device at a time. |
