Network Operating Systems (NOS) are the software that run on a server and enabling it to manage data, users, groups, security, applications, and other networking functions.

Upgrading a NOS is perhaps the most critical type of software upgrade involving significant, potentially drastic changes to the operation of your servers and clients.  As such, a great deal of forethought, product research, and rigorous evaluation is needed prior to the implementation of an NOS.  Common practice for such an endeavour in any network with more than a few users is the use of a project plan.

Amongst the most prominent reasons for upgrading an NOS are research, proposal, evaluation, training, pre-, during, and post implementation phases.