- Gateway: an interface providing a compatibility between networks by converting transmission speeds, protocols, codes, or security measures.
- Router: a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node. It works on OSI layer 3.
- Switch: a device that connects devices together on a computer network, by using packet switching to receive, process and forward data to the destination device. Unlike less advanced network hubs, a network switch forwards data only to one or multiple devices that need to receive it, rather than broadcasting the same data out of each of its ports. It works on OSI layer 2.
- Bridge: a device that connects multiple network segments. It works on OSI layers 1 and 2.
- Hub: for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming. A hub works at the physical layer (layer 1) of the OSI model. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision. Hubs are now largely obsolete, having been replaced by network switches except in very old installations or specialized applications.
- Repeater: an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.
Hybrid network devices include:
- Multilayer switch: a switch which, in addition to switching on OSI layer 2, provides functionality at higher protocol layers.
- Protocol converter: a hardware device that converts between two different types of transmission, for interoperation.
- Bridge router (brouter): a device that works as a bridge and as a router. The brouter routes packets for known protocols and simply forwards all other packets as a bridge would.
Hardware or software components which typically sit on the connection point of different networks (for example, between an internal network and an external network) include:
- Proxy server: computer network service which allows clients to make indirect network connections to other network services.
- Firewall: a piece of hardware or software put on the network to prevent some communications forbidden by the network policy. A firewall typically establishes a barrier between a trusted, secure internal network and another outside network, such as the Internet, that is assumed to not be secure or trusted.
- Network address translator (NAT): network service (provided as hardware or as software) that converts internal to external network addresses and vice versa.
Other hardware devices used for establishing networks or dial-up connections include:
- Multiplexer: a device that combines several electrical signals into a single signal.
- Network interface controller (NIC): a device connecting a computer to a wire-based computer network.
- Wireless network interface controller: a device connecting the attached computer to a radio-based computer network.
- Modem: device that modulates an analog "carrier" signal (such as sound) to encode digital information, and that also demodulates such a carrier signal to decode the transmitted information. Used (for example) when a computer communicates with another computer over a telephone network.
- ISDN terminal adapter (TA): a specialized gateway for ISDN.
- Line driver: a device to increase transmission distance by amplifying the signal; used in base-band networks only.
**Source - Alfacom Technologies website**