Network Topologies
Network topologies are categorized into the following basic types:
1. Bus Topology
2. Ring Topology
3. Star Topology
4. Tree Topology
5. Mesh Topology
Bus Topology
Uses single cable called Backbone to connect all device
To communicate the device broadcast the message
The message is seen by all the device
The message is accepted by the recipient only
Bus networks 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.
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.
Advantages of a Linear or Bus Topology
• Easy to connect a computer or peripheral to a linear bus.
• Requires less cable length than a star topology.
Disadvantages of a Linear or Bus Topology
• Entire network shuts down if there is a break in the main cable.
• Terminators are required at both ends of the backbone cable.
• Difficult to identify the problem if the entire network shuts down.
Ring Topology
It is in the shape of ring as name suggest
Token is used send message
Message travel in either "clockwise" or "counterclockwise" but not in both direction
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.
To implement a ring network, one typically uses FDDI (Fiber Distributed Data Interface), SONET (Synchronous Optical Network), or Token Ring technology. Ring topologies are found in some office buildings or school campuses.
Star Topology
It is widely used network topology
The shape of star topology resemble the shape of star
Hub is used to connect the device
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.)
Advantages of a Star Topology
• Easy to install and wire.
• No disruptions to the network then connecting or removing devices.
• Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
• Requires more cable length than a linear topology.
• If the hub or concentrator fails, nodes attached are disabled.
• 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.
Tree Topology
Hub is used as root of the tree
It follows hierarchical structure
Only hub connect with each other directly
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.
Advantages of a Tree Topology
• Point-to-point wiring for individual segments.
• Supported by several hardware and software venders.
Disadvantages of a Tree Topology
• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies.
Mesh Topology
Most difficult to implement and costly
Every device is connected with each other
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. (Recall that even in a ring, although two cable paths exist, messages can only travel in one direction.) Some WANs, most notably the Internet, employ mesh routing.
A mesh network in which every device connects to every other is called a full mesh. As shown in the illustration below, partial mesh networks also exist in which some devices connect only indirectly to others.
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