In Start Topology, all the computers are connected to the central located device called as hub. All the devices on the network are connected with a hub device through a communication link. Each computer requires a single wire for the connection to the hub.
A hub maybe a hub, a router or a switch.
In star Topology, there exists a point-to-point connection between a node and hub device. The hub device takes a signal from any node and passes it to all the other nodes in the network. The hub works as a server and it controls and manages entire function of the network.
If one host needs to send data to some other host, it will send the message to the central connecting hub device. The central connecting hub device then replicates the message and forwards it on to the appropriate host.
Depending on the network card used in each computer of the star topology, a RJ-45 network cable or a coaxial cable is used to connect computers together.
The picture to the down below shows how this network topology gets its name, as it is shaped like a star.
How does communication happen in a Star topology?
Let’s say all the computers of a computer lab are connected to a common hub (switch). The hub maintains a Content Addressable Memory (CAM) table in this case, where hardware addresses of the all the connected nodes are stored inside a memory in the switch.
For example, if computer X wants to send a data packet to computer Y then computer X will forward the message to the switch. The switch will check the address of the destination computer and forward the message to the same computer.
In the case of a hub device, a hub device does not have its own memory. So when computer X sends a message to computer Y, then hub announces “Hey I have got a message packet for this address. Who of you has this address?” This procedure is called as Address Resolution Protocol (ARP) and using this ARP protocol the hub is able to find the address of the intended computer and hence, it transfers the packet to the destination computer.
Characteristics of Star Topology:
- High Speed
- Very Flexible
- High Reliability
- High Maintainability
Advantages of Star Topology:
- Easy to manage and maintain the network because each node require separate cable.
- Easy to locate problems because cable failure only affect a single user.
- Easy to extend the network without disturbing to the entire network
- Due to Hub device network control and management is much easier.
- Fault identification and removing nodes in a network is easy.
- It provides very high speed of data transfer.
Disadvantages of Star Topology:
- Entire performance of the network depends on the single device hub.
- If the hub device goes down, the entire network will be dead.
- Star topology requires more wires compared to the ring and bus topology.
The star topology possess numerous advantages hence it is most widely used topology in today’s local-area networks (LANs).
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