Networking Guide

Introduction The OSI Reference Model
Physical Media Cat 5 Wiring Scheme
Network Components Network Topologies
Network Architectures Network Types
 
 

Networking Guide : Network Components

Hub

Hub is the central connection point in a network. Hub is used in a network that uses star topology. A sending computer transmits its signal to a hub, the hub then retransmits the signal to all other computers. A passive hub functions as a relay station that receives and retransmits signal. An active hub functions as a repeater that regenerates signal before retransmitting.

hub
Picture: Hub
When A sends to C, the Hub receives signal from A and retransmits it to both B and C.
Only C then processes the signal.

Using a hub, the network bandwidth (capacity) is shared by all available computers, therefore each computer only uses a portion of bandwidth. That's why hub is mostly used in small networks where there are only a few connected devices or computers. However, hub is not required if there are only two computers in a network. In that case, a direct connection using cable or wireless link can be used to connect both computers.

Switch

Like hub, switch works as the central connection point in a network. However when a switch receives a packet from a sending computer, it examines the destination address (i.e. MAC address of the destination computer) from the packet header and retransmits the packet to the destination computer only. That's possible because a switch maintains a table that maps all its ports with all connected devices' MAC addresses.

switch
Picture: Switch
When A sends to C, the Switch receives signal from A and only retransmits it to C.
B doesn't receive the signal.

Using a switch, the whole bandwidth can be used by each connected computer. That's why most big networks in which a large amount of data must be transferred at any given time, use a switch instead of hub. Switch is not always a separate device, it is very often integrated with router.

 
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Related links

Home Networking Guide : Ethernet