A hub has multiple ports such as 6, 8, 16 and 24 etc. When data packets are reached at hub, they are broadcasted to all the computers unlike a switch and only the destined computer receives the data. When you want to connect more than computers with each other a hub or switch is required in a local area network. There are two types of a hub passive hub and active hub.
LAN card, network interface card or NIC is used to join the computers in a network. A NIC card is installed in any available PCI port inside the computer. A unique MAC (Media Control Access) address is assigned to LAN card. A MAC address is consists of two portions manufacture’s id and the card id (PROM on the network interface card holds the addresses). LAN card operates on the physical and data link layer of the OSI model. A LAN card usually has twisted pair, BNC and AUI sockets where the Ethernet cables are connected.
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.
A repeater is a network device that is used to retransmit the weaker signals in a network. A repeater receives the signals on the electromagnetic or optical transmission mediums. Repeater removes the unwanted noise from the incoming signals. A series of the repeaters is used to amplify the signals in the big network. The can also relay the messages between subnetworks that use different protocols but a repeater can’t perform intelligent routing like the routers.
A router is a network communication device that is used to connect two or more logically and physically different networks. A router can be used to connect a LAN to LAN, LAN to WAN and LAN to internet. A router acts as a post office where sorting and distribution of the posts (packets in case of routers) is done. A router works on the basis of an IP address. Every router has built-in operating system known as IOS. A router works on the network layer of the OS model and it routes the data towards the optimal path. Router uses the header information of the packets and forwarding table to define the best shortest possible path of the data.
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.