Communication Topology and It's Classification

**Communication Topology: Topology is physical layout of a communication network. Two communication devices are connected by a link and two or more link creates a topology.

**Types of topology:
                                1. Mesh
                                2. Star
                                3. Bus
                                4. Ring

1.       Mesh topology: 
    --> Every device has a dedicated p-2-p link to every other devices.
Advantages: Dedicated links, so guaranteed transmission.
                        Robust topology
                        Privacy/security topology
Disadvantages: Huge number of cabling.
                             Huge cost of installation
                             Installation and Reconnection is difficult.

2.       Star topology: 
     --> Each device has a dedicated p-2-p link only to a central controller called HUB.--> The central controller should have the intelligence about where from the data/info receive and where to send.
Advantages: Need less cabling than Mesh
                        Installation is easy
                        Robust topology
Disadvantage: If the central controller is disable then the whole topology will disabled.

3.       Bus topology:
--> It is multipoint
--> One long cable acts as a backbone cable to link all the devices in a network.
--> All the devices connected to the backbone cable by a drop line and tab.
Advantages: Easy installation
                        Less cabling
                        Backbone cable can be a efficient path
Disadvantages: Difficult reconnection and Fault isolation.
                             It can be difficult to add new device.

4.       Ring topology:
--> Each device has a dedicated p-2-p connection only with the two devices on either side of it.
-->signal passed along the ring.
Advantages: Relatively easy to install and reconfigure.
                        To add or delete a new device requires changing only two connections.
Disadvantages: Unidirectional traffic
                             A break in the ring can disable the entire network.

## The device between the transmitting device and receiving device is called HOP.

**One direction: From device to device until it reaches its destination. Each device acts as a repeater.