2. ISDN(Integrated Services Digital Network) The ISDN (ISDN, Integrated Services Digital Network, synthesis digital network service) is the digital line network which packet transmission / circuit switching data communication digitized to a switchboard / trunk / member line entirely can use.

5. IP(Internet Protocol) Internet Protocol address distinguishes a side near the network part and LSB (least significant bit) as a host part with a side near MSB (most significant bit). The network part specifies the network, and the host part specifies the equipment in the network. The subnet mask is used for the distinction between the network part and the host part.