I came across an article which States that we can have mixed os in cluster.
Article talk about having flannel as networking plugin but i want to use Calico opensource plugin instead as it provides encryption.
Any idea if this is possible using Calico opensource?
Calico for Windows does exist https://www.tigera.io/tigera-products/calico-for-windows/
But it appears to be a commercial product so you would probably want to contact them to ask about it. Assuming it's equivalent to normal Calico, I don't see any reason it wouldn't work. BGP and IPIP are both standardized protocols that aren't specific to any OS.