Hubs/Repeaters are used to connect together two or more network segments of any media type. In larger design, signal quality begins to deteriorate as segment exceeds their maximum length. A hub provides the signal amplification required to allow a segment to be extended a greater distance.
Passive hub simply forwards any data packets they receive over one port from one workstation to all their remaining ports. Active hubs, also sometimes referred to as "multiport repeaters", regenerate the data bits in order to maintain a strong signal.
Bridges: The bridge function is to connect separate homogeneous networks. Bridges map the Ethernet address of the nodes residing on each network segment and allow only necessary traffic to pass through the bridge. When a packet is received by the bridge, the bridge determines the destination and source segments.
If the segments are different, then the packet is "forwarded" to the correct segment. Bridges are also called "store-and-forward" device because they look at the whole Ethernet packet before making filtering or forwarding decisions.
Router: Routing achieved commercially popularity in the mid – 1980s – at a time when large-scale Internetworking began to replace the fairly simple, homogeneous environments. Routing is the act of moving information across an Internetwork from a source to a destination. It is often contrasted with bridging, which perform a similar function.
Routers use information within each packet to route it from one LAN to another, and communicate with each other and share information that allows them to determine the best route through a complex network of many LANs.
Switches: LAN switches are an expansion of the concept in LAN bridging, which controls data flow, handles transmission errors, provides physical addressing, and manages access to the physical medium. Switches provide these functions by using various link-layer protocols. LAN switches can link four, six, ten or more networks together. A store-and-forward switch, on the other hand, accepts and analyses the entire packet before forwarding it to its destination.
Transceivers: Transceivers are used to connect nodes to the various Ethernet media. Most computers and network interface cards contain a built-in 10BaseT or 10Base2 transceiver, allowing them to be connected directly to Ethernet without requiring an external transceiver. Many Ethernet devices provide an AUI connector to allow the user to connect to any media type via an external transceiver.
Gateway: A computer that controls the traffic of your LAN or your ISP receives is a Gateway. A server serves as a Gateway, the gateway also works as a firewall and a proxy server. A Gateway is a device such as a mini or microcomputer capable of operating on a stand alone basis but which also provides connection for communication with the other computers and access to shared resources.
Normally a gateway is associated with a router. A router is a device that lets you know the next network data should be sent to next. A router can be connected to more than one network at a time. A gateway is associated with a router because a router which uses headers and forwarding tables to figure out where packets or data is sent provides the path through which information is sent in and out a gateway.
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