Types of Network & Topology


Types of Networks

I’ll just make you to skim through types of network and topology. I’m not gonna discuss every nook and cranny of Networking concepts here. Generally Networks were categorized based on the geographical size. I repeat again, based on it’s geographic distance but not the numbers of systems you have. So we have few types in it.

LAN: A Local area network is a network in which computers are relatively close together, such as within the same office or building. But again this doesn’t mean that LAN is a small network, LAN may have thousands of systems connected. What makes a network a LAN is that all those systems are within close proximity to each other. You need an example? You ever played Counter Strike LAN Gaming? if not, never mind, just think about your office or may be cyber cafe.

WAN: A Wide area network is a network used to connect two or more LANs that are relatively far apart. Let’s take your example again, a WAN may connect your office in Hyderabad with your office in Bangalore. If you notice, I didn’t even mention about the systems your office contains. All the time I was saying geographic distance.

MAN: A Metropolitan area network, is a network that’s smaller than a typical WAN but larger than a LAN. MAN connects two or more LANs that are within the same city but are far enough apart that the networks can’t be connected using a simple cable or wireless connection. Lets say MAN may connect your office in Hyderabad – X Street with your office in Hyderabad – Y Street itself. Don’t get muddled, it’s entirely based on the geographic distance. Okay, just see the Image below. Don’t ask me where did I get this Image from. Now it makes sense right?
LAN-MAN-WAN

Network Topology

Topology refers to the way in which the network of computers is connected. Each topology is suited to specific tasks and has its own pros and cons. The choice of topology is depends upon type and number of equipment being used, rate of data transfer required, response time, and cost. Before diving into the types of Topology, you need to know What is a Packet? Chill, it’s just a Message.

Packet: A packet is a message that sent over the network from one system to another system. The packet includes the address of the system which sent the packet, the address of the system where the packet is being sent to. In technical words, we can call as Source and Destinations.

Back to the Topology again, there are Various commonly used topology, wanna know about them? Okay go ahead.
1.Bus topology
2.Star topology
3.Expanding stars
4.Ring topology
5.Mesh topology

Bus Topology

In this topology all the systems/components in entire network connected as a single cable, with each system can listen in on the packets being sent over that cable. In a bus topology, every node on the network can see every packet that sent on the cable. Each system/computer looks at each packet to determine whether the packet is intended for it or not. If so, the node claims the packet. If not, the node ignores the packet. This way, each computer can respond to data sent to it and ignore data sent to other computers on the network. If the cable in a bus network breaks, the entire network is effectively disabled. Okay, you need an example? Let’s go to baggage claim area in the Airport. We only look for our packets and we ignore others packets right? And assume, what happens if the thread has been stopped? You can’t get your packet and Nobody else gets the packet. Similarly Bus Topology works. I know this is some bad example but trust me this is how I’ve learnt.

080725-mad-airlines-hmed4p

Key Characteristics of this topology are:
o Flexible
o Expandable
o Moderate Reliability
o Moderate performance

Star Topology

In a star topology, each network node is connected to a central device called a hub or a switch. If a cable in a star network breaks, only the node connected to that cable is isolated from the network. The other nodes can continue to operate without interruption. If the network uses a hub, the network topology has the physical appearance of a star, but is actually a bus. That’s because when a hub is used, each computer on the network sees all the packets sent over the network, just like in a bus topology. In a true star topology, as when a switch is used, each computer sees only those packets that were sent specifically to it.
Okay Okay, you may think what on earth is a Hub and a Switch?

Hub: Hub is typically the least expensive, least intelligent. Its job is very simple guys, anything that comes in one port is sent out to the others. That’s it. If a message1 comes in for computer “A”, that message is sent out all the other ports, regardless of which one computer “A” is on.

Switch: It knows on which connection the sender of the message is located. Thus, when machine “A” responds to the message, the switches only need to send that message out to the one connection.

Key Characteristics of this topology are:
o High Speed
o Very Flexible
o High Reliability
o High Maintainability

Expanding stars

A bus can be used to connect several stars. In this case, two or more hubs or switches are connected to each other using a bus. Each of these hubs or switches is then the center of a star that connects two or more computers to the network. This type of arrangement is commonly used in buildings that have two or more distinct workgroups. The bus that connects the switches is sometimes called a backbone. Another way to expand a star topology is to use a technique called daisychaining. When you use daisy-chaining, a switch is connected to another switch as if it were one of the nodes on the star. Then, this second switch
serves as the center of a second star.

Ring Topology

In a Ring topology, packets are sent around the circle from computer to computer. Each computer looks at each packet to decide whether the packet was intended for it. If not, the packet is passed on to the next computer in the ring.

Mesh Topology

This has multiple connections between each of the nodes on the network. The advantage of a mesh topology is that if one cable breaks, the network can use an alternative route to deliver its packets. Mesh networks aren’t very practical in a LAN setting. For example, to network eight computers in a mesh topology, each computer would have to have seven network interface cards, and 28 cables would be required
to connect each computer to the seven other computers in the network. Obviously, this scheme isn’t very scalable. However, mesh networks are common for metropolitan or wide area networks. These networks use devices called routers to route packets from network to network. For reliability and performance reasons, routers are usually arranged in a way that provides multiple paths between any two
nodes on the network in a mesh-like arrangement.

Key Characteristics of this topology are:
o Fully connected
o Robust – Highly reliable
o Not flexible

Okay, we’re done with types and topologies now. Thanks for reading. I’ll post few more articles on networking soon. I would suggest you to watch videos on youtube to learn these concepts very quick.

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