A network segment (in computer science) is a logically or physically isolated part of a network .
The network is divided into segments in order to optimize network traffic and / or increase the security of the network as a whole.
Physical separation
As a rule, the physical network segment is limited to a network device that connects the nodes of the segment to the rest of the network:
- Switches ( Layer 2 in the OSI model )
- Routers (Layer 3 in the OSI model )
The physical network segment is a collision domain . Devices operating on the first level of the OSI model (repeaters or hubs) do not limit the collision domain.
Logical separation
It is widely practiced to divide an IP- based network into logical segments , or logical subnets. To do this, each segment is allocated a range of addresses , which is defined by the network address and network mask . For example (in CIDR records):
- 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24, etc. - in each segment up to 254 nodes
- 192.168.0.0/25, 192.168.128.0/26, 192.168.172.0/27 - in segments up to 126, 62, 30 nodes, respectively
Logical subnets are connected via routers .
Literature
- RFC 4632 (Eng.) Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan