Network segmentation involves partitioning a network into smaller networks; hence we can then say that Network segmentation is a way of dividing a big network (we can consider a network as a Broadcast Domain) into subnet, so that will be on its own, each, acting as a network segment or network layer.
A big network can be segmented to smaller subnets using a Router. It is important to note that When implementing network segmentation, the aim is to restrict the level of access to sensitive information, hosts and services while ensuring an organization can continue to operate effectively. For this reason, if network segmentation must be effective, network segmentation measures must be carefully planned, robustly enforced, closely monitored and be unable to be bypassed.
As the number of devices in the Broadcast Domain increases, number of Broadcasts also increases and the quality of the network will come down because of the following reasons.
1) Decrease in available Bandwidth: Large number of Broadcasts will reduce the available bandwidth of network links for normal traffic because the broadcast traffic is forwarded to all the ports in a switch. Every device in the broadcast domain will receive the broadcast.
2) Decrease in processing power of computers: Since all the computers need to process all broadcast packets, a huge portion of the computer CPU power is spent on processing the broadcast packets. This will reduce the processing power of computers.
By default, routers don’t pass broadcasts from one network segment to another network segment and therefore restrict the broadcast within the Broadcast Domain.
By segmenting a big broadcast domain into smaller smaller broadcast domains, we can keep the local broadcast traffic local. Routers drop unwanted traffic originating from one network to pass through the router to reach another network, thus increasing the bandwidth available to each user.
Another benefits of network segmentation using Routers include
Routers are used to connect networks of different media types. For example, one of your network segment may be using Tokenring as LAN Standard (just as an example, Tokenring is out from industry long way back) and other network segment is using Ethernet as the LAN Standard. A Router can be used to connect these different LAN Standards.