Networking concepts

Hub, Repeater, Switch, Bridge, Router and Gateway

   Major differences between different networking devices are mentioned in this table.

Network Devices	OSI layer corresponds to the Device	Functions
Hub	Physical	Multiport repeater. Any electrical signal that comes into one port, goes out of all other ports. Does not examine or manage traffic.
Repeater	Physical	Regenerates the signal. Connects two segments of a network cable. Extends physical length of network. Is a re-generator not an amplifier. Active hubs.
Switch	Data link	Connects n/w segments or n/w devices. Is a multipoint network bridge(bridge with numerous o/p ports). Process and routes data to the intended receiver. Intelligent than hub. Multilayer switch works on Data link and Network layer. Reduces traffic and divide the collision domain into segments. Uses MAC address for communication.
Bridge	Data link	A combination of hardware and software to link two similar networks. Divides a large network to smaller segments. Very much alike switch. Does data filtering and separating the collision domain like switch. Slower compared to switch since it uses s/w for switching. Controls congestion and isolation. Uses MAC address for communication.
Router	Network	Route data packets between different networks of same type. Can connect networks with different architecture like Token Ring and Ethernet. Cannot connect networks of different protocols like TCP/IP and IPX/SPX. Controls both collision domains and broadcast domains. Uses IP address for communication. Ability to identify best route for the packet to travel using a routing table.
Gateway	Application, Network, Session	Interconnects networks with different network protocol technologies by performing the required protocol conversions. Very intelligent device Works at network layer and above, but mostly work at application layer. Mostly it is a software installed in router.