A Hub is simple device used to connect two computers or more then two computers to enable communication between them. In other words a Hub is a multiport repeater which sends the data to other network. Now let us understand one basic network to understand the function of hub.
Basic Network using Hub
Basic Network using HubAs shown in the figure two computers lets say Sid and Melly are connected to each other with the help of HUB. Now for example if Sid wants to communicate with Melly then what will he do ? Sid doesn't even know the IP address of Melly then how will he able to communicate? There are lots of question about communication taking place between them.
Now Sid knows only two things, first is IP Address of himself that is 192.168.10.2 and MAC Address(Hardware Address that is given by the company) of himself that is 00:3b:4c:00:34:cc. IP Address of Melly is 192.168.10.3 and MAC Address is 00:3b:5c:11:as:cc as shown in the figure. But these Addresses of Melly are not seen or known by Sid.
So now what Sid will do is, he will just send message “Hi, Melly” to the HUB. He is actually not knowing that where his data/message is going. Now when the message reaches HUB , and now what is HUB going to do is it will broadcast the message sent by the Sid(Source) to all the Computers attached to its port.
Source Destination192.168.10.2 192.168.10.255
So as shown above Sid’s message will be broadcasted to all the Computers attached to the HUB, because HUB will consider the Destination Address as 192.168.10.255. Now as data is sent to all the computers, Melly will also receive it. And all other computer will also receive the same, but now out of all the person whose name is Melly will send back the Message with its IP Address as well as its MAC Address to the Source.
( Actually Sid’s IP Address and his MAC Address will be broadcasted like follows
source : 192.168.10.2(00:3b:4c:00:34:cc)
Destination: 192.168.10.255(FF:FF:FF:FF:FF:FF)
)
So in this way Sid can come to know the IP Address of Melly. Melly will send ARP(Address Resolution Protocol) to the Sid, and it will be containing the IP Address of her and also MAC Address. So now the Destination for the Melly will be Sid’s IP Address and MAC Address to send ARP.
Source Destination
192.168.10.3(00:3b:5c:11:as:cc) 192.168.10.2(00:3b:4c:00:34:cc)
Now both of them are having the things they need to communicate with each other. This is how communication take place in HUB.
Disadvantages of HUB
- It is Layer 1 device
- Cannot break Broadcast Domain as well as Collision Domain
- Low Bandwidth
- High Traffic of data
Reason of Collision and high Traffic while using HUB
Suppose that one network is created using HUB. Assume, in that network 50 computers are connected via HUB. Now if all of them starts sending data at a same time then HUB will broadcast all the data to each of the computer connected to its port. So main reason to this traffic and collision is the broadcast. If the number of computer increases in the network traffic will increase and whole network can go down. That is why Bridges and Switches came in market to resolve this kind of problem of the HUB.
Important Point about HUB: HUB works with one Broadcast Domain as well as one Collision Domain
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