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"Network domain" is a term used[by whom?] to differentiate between multiple private computer networks within the same infrastructure. The term is unofficial and has mostly spread through word of mouth.
Half of the staff of Building A uses Network 1, 192.168.10.0/24. This network has the Vlan identifier of Vlan 10
The other half of the staff of Building A uses Network 2, 192.168.20.0/24. This network has the Vlan identifier of Vlan 20
All of the staff of Building B uses Network 3, 192.168.0.0/24. This has the Vlan identifier of Vlan 11.
The router R1 serves as the gateway for all three networks, and the whole infrastructure is connected physically via ethernet cable. Networks 2 and 3 are routed through R1 and each has full access to the other.
Network 1 is completely separate from the other two, and will not have access to either of them. Network 2 and 3 are therefore in the same network domain, while Network 1 is in its own network domain, albeit alone.
These network domains can then be suitably named[by whom?] to match the infrastructure terminology.
While not a recognized standard term within networking circles, the phrase "network domain" meets the need for network administrators to separate different networks which use the same IP address-range, and has thus formed the term which is now[when?] widely[quantify] used[by whom?] in certain[which?] geographic areas.
Compare: Anderson, Howard; Yull, Sharon; Hellingsworth, Bruce (2001). Higher National Computing (2 ed.). Oxford: Routledge (published 2004). p. 260. ISBN 9781136398988. Retrieved 2015-08-18.
A network domain is more formally defined as a group for servers controlled by a primary domain controller. The idea is that this group of servers can behave as a single combined unit.
Chen, Lidong; Gong, Guang (2012). Communication System Security. Chapman & Hall/CRC Cryptography and Network Security Series. CRC Press. p. 313. ISBN 9781439840368. Retrieved 2015-08-18.
The terminology, network domain, comes from the cellular systems. Traditionally, a cellular service provider owns not only radio frequency spectrums but also certain network infrastructure, for example, base stations, switches, and servers. All these entities are connected through wired network to provide telephony service. A network domain is the wired portion of an operator's network.