Basics of networking

The logical network topology includes:

·         peer to peer,

·         pass the token,

·         multiple access.

Point-to-point logical topology

In a point-to-point topology, data is only transmitted from one device to another. These devices can be connected to each other directly, e.g. a computer to a switch, or indirectly, over long distances, using an intermediate device, e.g. connecting two routers several kilometres apart.

In both cases, we can talk about logical point-to-point connections. This is a logical topology, often used in LANs that use a physical star topology.

Logical topology for token transfer

In a topology with token passing, data is passed sequentially to network devices. The device that receives a batch of data analyses it to see if it points to it. If the data is not intended for it, it will forward it to a neighbouring device. In this way, all devices transfer data between source and destination devices.

Multiple access logical topology

Multi-access topology (sometimes also called broadcast or logical bus topology) allows devices on a network to communicate over a single physical transmission medium. It was mostly used with physical bus and star topologies in the early stages of its development, when hubs were still used as network access points.

Every device in this topology can see the data sent over the network, as it is sent to all devices, but only the specific device to which the data is addressed can interpret it. As the devices in the network share a common medium, it is necessary to implement mechanisms to control access to this medium, these are: CSMA/CD, CSMA/CA and token pass.

Link (network) access method

The CSMA/CD method, a collision detection method, involves monitoring the state of the link. If the device that is to start a transmission detects that the link is idle, it starts such a transmission. If, during the transfer, it detects that another device on the network is also sending its data, the transfer will be interrupted. After a while, it retries the transfer. Older versions of Ethernet use this mechanism.

The CSMA/CA method, a collision avoidance method, also involves monitoring the state of the link, but detecting that the carrier, i.e. the device where the transmission medium is idle, starts by sending information about its intent before transmission begins. This mechanism exists in wireless networks.

The token transfer method involves sending a special piece of data called a token from device to device, possession of which initiates the transfer.