Hubs
Hubs also called wiring cocentrators . Provide a central attachment point for network cabling . Hubs come in three types.
1] Passive
2] Active
3] Switching
The following sections describe each pf these type e in more detail.
Passive Hubs:-
Passive hubs do not contain any electronic components and do not process the data signals from several network cable segments . All devices attached to a passive hub receive all the packets that pass through the hub.
Because the hub dosent clean up or amplify the signals (in fact , the hub absorbs a small part of the signal.) the distance between a computer and the hub can be more than half the maximum permissible distance between two compuiters on the network ...
Ex:-
If the network design limits the distance between two computer to 200 meters, the maximum distance between a computer and the hub is 100 meters.
As you might guess , the limited functionally of passive hubs makes them inexpensive and easy to configure. That limited functonility however , is also thew biggest disadvantges passive hubs , due to the fact that there are few machins on the LAN and small distances between them . Hubs follow the 5-4-3 rule , where no more than 5 network segments can be connected to 4 hubs with only only 3 of them being populated.
Active Hubs:-
Active hubs incorrect electronic compoinents that can amplify and clean up the electronic signals that flow between devices on the network .this process of cleaning up the signals is called signal regenration has the following benifits.
1] The network is more robust (less sensitive to errors).
2] Distance between devices can be increased.
These advantages genrally owtweight the fact that active hubs cost considerably more than passive hubs.
Earlier in this chapter, you l;earned about repeater ,devices that amplify and about repeater ,devices that amplify and regenrate network signals . Beause active hubs function in part as repeters assasionally are called multiport repeaters.
Intelligent Hubs:-
Intelligent hubs are enhanced active hubs.Several functions can add intelligence to hub:
1] Hub management:-
Hubs now support network management protocols that enable the hub to sent packts to a central network console. These protocols also enable the console to control the hub; for example,a net word adminitrator can order the hud to shutdown a connection that is generating network erros.
Switching Hub:-
The latest developement in hubs is the switching hub which includes circuitry that very bad, a switching hub repeates a packet. Many switching hubs have the capablity of switching hub are replacing briges and routers on many networks.
In essance,a switching hub acts like a very fast bridge , which is what described in the next section . Switching hubs are the most expencive of hubs on the market .Often they are simply reftered to as switches . As for the exam think of all types of hubs as simply a hub.
Routers, Hubs, Repeaters, Bridges, Modems, Switches
