Network Topologies : Strucuture of Network

Computer network topology is the way various components of a network (like nodes, links, peripherals, etc) are arranged. Network topologies define the layout, virtual shape or structure of network, not only physically but also logically. The way in which different systems and nodes are connected and communicate with each other is determined by topology of the network.
Topology can be physical or logical. Physical Topology is the physical layout of nodes, workstations and cables in the network; while logical topology is the way information flows between different components.

So We can say that Topology is arrangment of Networking Devices

Now we will discuss various types of Network Topologies…

Star Topology

Many home networks use the star topology. A star network features a central connection point called a “hub” that may be a hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.
Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer’s network access and not the entire LAN. (If the hub fails, however, the entire network also fails.)

 star topology

Advantages of a Star Topology
  1. Easy to install and wire.
  2. No disruptions to the network then connecting or removing devices.
  3. Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
  1. Requires more cable length than a linear topology.
  2. If the hub or concentrator fails, nodes attached are disabled.
  3. More expensive than linear bus topologies because of the cost of the concentrators.
The protocols used with star configurations are usually Ethernet or LocalTalk. Token Ring uses a similar topology, called the star-wired ring.

Ring Topology

In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either “clockwise” or “counterclockwise”). A failure in any cable or device breaks the loop and can take down the entire network.

network topologies

To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses.

Bus Topology

Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.
Ethernet bus topologies are relatively easy to install and don’t require much cabling compared to the alternatives. 10Base-2 (“ThinNet”) and 10Base-5 (“ThickNet”) both were popular Ethernet cabling options many years ago for bus topologies. However, bus networks work best with a limited number of devices. If more than a few dozen computers are added to a network bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable.

Image result for bus topology

Advantages of a Linear Bus Topology
  1. Easy to connect a computer or peripheral to a linear bus.
  2. Requires less cable length than a star topology.
Disadvantages of a Linear Bus Topology
  1. Entire network shuts down if there is a break in the main cable.
  2. Terminators are required at both ends of the backbone cable.
  3. Difficult to identify the problem if the entire network shuts down.
  4. Not meant to be used as a stand-alone solution in a large building.

Tree Topology

Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the “root” of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points) alone.
network topologies
Advantages of a Tree Topology
  1. Point-to-point wiring for individual segments.
  2. Supported by several hardware and software venders.
Disadvantages of a Tree Topology
  1. Overall length of each segment is limited by the type of cabling used.
  2. If the backbone line breaks, the entire segment goes down.
  3. More difficult to configure and wire than other topologies.

Mesh Topology

Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination.

mesh topology network topologies

Advantages of Mesh topology
1) Data can be transmitted from different devices simultaneously. This topology can withstand high traffic.
2) Even if one of the components fails there is always an alternative present. So data transfer doesn’t get affected.
3) Expansion and modification in topology can be done without disrupting other nodes.
Disadvantages of Mesh topology
1) There are high chances of redundancy in many of the network connections.
2) Overall cost of this network is way too high as compared to other network topologies.
3) Set-up and maintenance of this topology is very difficult. Even administration of the network is tough.

Hybrid Topology

A combination of any two or more network topologies. Note 1: Instances can occur where two basic network topologies, when connected together, can still retain the basic network character, and therefore not be a hybrid network. For example, a tree network connected to a tree network is still a tree network. Therefore, a hybrid network accrues only when two basic networks are connected and the resulting network topology fails to meet one of the basic topology definitions. For example, two star networks connected together exhibit hybrid network topologies.

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