A hub is a networking device, which is used to connect the two segments of a wired network.
A network switch performs the same functionality in a network as a hub except a different that switch does not broadcast the data packets to all the computers in a network like a hub. A network switch has multiple ports like 4, 8, 16 and 24 etc. All the computers in a wired network are directly connected with the switch through Ethernet cable. Switches limit the traffic to and from each port and all the devices connected to the switch has maximum available bandwidth. Switch doesn’t provide the built-in firewall capabilities like the routers. In the telecommunication and packet switched infrastructure switches play an important role. They transmit the data towards its destination based on the IP address.
A gateway can be hardware or software and it acts as a bridge between two networks. A gateway is an entrance point of a network. A gateway connects a LAN with internet. A router acts as a gateway device in a network. In big networks, a computer server which acts as a gateway also acts as a proxy server and a firewall server. A gateway computer is usually attached with the router and switch.
ISDN (Integrated Services Digital Network) is a data communication method and it is used over the regular telephone lines. To use the ISDN lines, you need to install add-on adapters known as ISDN terminal adapters. ISDN Terminal Adapter works like a digital modem i.e. it converts the signals from digital to analog and vice versa. ISDN Terminal adapter is plugged into the serial port of the system. Some ISDN adapters have the feature of switching between digital and analog modes.
CSU/DSU stands for channel service unit and data service unit. CSU is used to connect a terminal to a digital line. DSU is used to perform the protective and diagnostic functions of the telecommunication line. CSU/DSU is a network device of the size of an external modem. The Channel service unit receives and transmits the signals from the wide area network line. CSU/DSU are two separate devices and they are sometimes used in conjunction with the T1 LAN cards.
A bridge is a network communication device that is used to connect two segments of a LAN that uses the same protocol. Bridge is like a router but it doesn’t analyze the data before sending. A bridge operates at the data link layer of the OSI model and it can be used to connect the physically different networks and the networks that use the different protocols such as Ethernet and Token Ring.
A modem is communication device that performs two different functions such as modulation and demodulation i.e. it converts the digital data into analog and analog into digital. The faster types of the modems are used by the internet such as DSL modem, cable modem and optical modems. The features like BPS, auto answer, data compression, voice/data, fax capability and flash memory distinguish one modem from the other.
Network bridge and router combined together to form a device known as brouter.