hi Manoj -
The idea of Site-ID is used in the context, say, if the controllers are spun in AWS in different region/AZ {East and West},
you would have the controllers in one region/AZ with the same site-ID and in the other region in a different site-ID.
This is especially true for vSmart. vManage is typically is a stand-alone and is in one region only. {Even for a cluster}
This requirement doesn't apply for vBond.
HTH.