Device Modeling

Terry Slattery
Principal Architect

Some network configuration management vendors are building systems that model network devices.  Their intent is that their customers will find that working with a model of a router or switch will be easier than working with a larger number of individual device types.  The alure to the network configuration vendor is that they can write one set of policies and apply it to a wide number of devices. There are at least two reasons why this strategy won’t work.

The first reason has to do with training customers on the generic model.  That’s the crux of the problem — it is a new syntax that the customer must learn.  Instead, should the vendor choose a device-independent syntax or design around the leading equipment vendor’s syntax?  Both approaches are fraught with problems.

If a new language is used, the customers must be trained on the language, which is a significant burden on the network management vendor as well as the customers.  If a major equipment vendor’s language is used, that creates a burden on the customer to remember which syntax to use for the network management system and on the device itself.   I see a large number of human errors occurring in these scenarios.  There are also enough variations between similar hardware of major vendors that this choice has significant problems.

The second problem is that for a given problem, it is practically impossible to use a generic model to match that of real configurations.  My prime example is QoS configuration where the variation between devices is too great to handle.  The underlying hardware, often the ASICs themselves, drive changes in syntax between devices.  Even Cisco’s attempt at a single command set, the Modular QoS CLI, has many subtle variations.  It gets even more challenging when other vendors are considered.

The only solution I see that is workable is to use the CLI syntax of each device type, just as network engineers have to do in the real world.  They already deal with the variations and understand them.  Why complicate their lives with yet another variation?



Re-posted with Permission 

NetCraftsmen would like to acknowledge Infoblox for their permission to re-post this article which originally appeared in the Applied Infrastructure blog under


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