This variable indicates the firmware installed on this entity.
For IOS devices, this variable's value is in the IOS Image
Naming Convention format.
IOS Image Naming Convention
Software images are named according to a scheme that identifies
what's in the image and what platform it runs on. The names have
three parts, separated by dashes: e.g. xxxx-yyyy-ww.
xxxx = Platform
yyyy = Features
ww = Where it executes from and if compressed