A security domain is the determining factor in the classification of an enclave of servers/computers. A network with a different security domain is kept separate from other networks. Examples: NIPRNet, SIPRNet. JWICS, NSANet are all kept separate. A security domain is the determining factor in the classification of an enclave of servers/computers. A network with a different security domain is kept separate from other networks. Examples: NIPRNet, SIPRNet. JWICS, NSANet are all kept separate.