The network topology, the layout, and connections of the network hardware
The number of host systems your network can support
The types of hosts that the network supports
The types of servers that you might need
The type of network media to use: Ethernet, Token Ring, FDDI, and so on
Whether you need bridges or routers extend this media or connect the local network to external networks
Whether some systems need separately purchased interfaces in addition to their built in interfaces
Based on these factors, you can determine the size of your local area network.