What is meant by ring topology

IT networks

Network topology

Topology is the study of the position and arrangement of geometric structures in space (corresponds to the Duden foreign dictionary). The network topology describes how the network components or nodes are physically connected to form the network structure. The network nodes include active and passive components. In the case of computers, strictly speaking, it is only the network cards. Nodes are also peripheral devices such as printers, scanners and network components such as repeaters, hubs, routers and switches, which are required to connect and expand networks. The physical connections can be wired or wireless. The three basic topologies are ring, star and bus structure. They can be combined to form more complex topologies such as tree and mesh structures.

Bus structure

All nodes are connected to a central line, the bus. The bus is formed by a coaxial cable RG-58 with 50 Ω impedance, which must be terminated at its open ends with 50 Ω resistors to avoid signal reflections. The components are connected via coaxial BNC-T adapters. There are no active components for signal processing between the nodes and the nodes also behave passively in this regard.

The best-known example of this bus structure is Ethernet in its simplest form, 10Base-2, with a data rate of 10 Mbit / s. It is also called Thin-Wire-Ethernet, Thinnet or Cheapernet. A cable segment is limited to 185 m. A maximum of 30 nodes can be connected. The cable length between two nodes must be at least 0.5 m.

With direct data transfer using the baseband method, only the signals from one node can be sent undisturbed on the bus. If a second node sends signals on the busy bus, an overlay occurs, which is referred to as a collision. The data can no longer be used.

Special advantages of a bus topology
Simple, inexpensive cabling.
Easily add and remove network nodes.
No active network components are required in the segment.
The failure of a node has no effect on network functionality.
Important disadvantages of a bus topology
A single defect in the bus line or a missing termination blocks the entire bus segment.
The segment length and the number of nodes are limited due to the lack of data regeneration.
As long as one node is transmitting, all other nodes have to wait.
Collision detection and prevention protocols are necessary for optimal data traffic.

Star structure

All network nodes are connected directly to a central node. The central node can be an active or passive network component. The terminal computer and the client-server system shown above are connected in a star topology to the central computer as an active node. The peer-to-peer network with a central passive hub or active multiport repeater is physically connected in a star structure. The data traffic always goes through the central node.

The wiring is mostly done using twisted pair cables with RJ45 connectors. The number of nodes is determined by the connection options provided by the central node. The normal data rate reaches 10 Mbit / s. The data traffic via the central node corresponds to a point-to-point connection.

Main advantages of a star structure
Simple, easy to understand and service-friendly structure.
Nodes can be added or removed on the fly.
The failure of a node has no effect on the network.
Central management of all nodes and connections.
High transmission rates if the central node is an active network component.
Particular disadvantages of a star structure
The failure of the central node blocks the entire star structure.
High quality standards at the central node or doubling it increases the costs.
With a passive hub, the transfer rate decreases the more nodes want to participate in the data traffic.

Ring structure

All components in the ring have equal rights and are only connected directly to the predecessor and successor via their network card, the actual node. The data traffic traverses the entire ring in a specified direction. Since the network cards have repeater functions and regenerate the data signals, a large number of nodes can be connected to form large ring structures. The failure of a component blocks the entire ring. With a double ring structure, the network is given a redundancy that can intercept and prevent this type of error. With fiber optic cables, data rates of up to 100 Mbit / s and distances of up to 200 km can be achieved. With the token passing, the data traffic requires a special transport protocol with addressing. The best-known ring structure is the token ring.

Advantages of a ring structure
Simple structure and expandability in the event of interrupted network operation.
All network nodes have equal rights and regenerate the signals.
Many participants can be connected in a large ring.
There is no data collision and a guaranteed bandwidth.
Important disadvantages of a ring structure
The failure of a network component blocks the entire ring in the single-ring topology.
Expensive components with active nodes for failure protection and special transport protocols.
The transmission time increases with large rings and distant targets.

The picture on the left shows the simple ring topology, with the active network component being the network card built into the workstation. The picture on the right is an improved ring network secured against station failures. The workstations and hosts are connected to the actual ring components in a star configuration with twisted pair cables. Several of these active ring line distributors (RLV) or multistation access units (MAU or MSAU) can be combined to form a large ring system. They automatically recognize connected or disconnected hosts and loop through the data signals accordingly. The ring connection with fiber optic cable allows data rates of up to 100 Mbit / s. The procedure is specified up to 1 Gbit / s. Another chapter provides information on cable types and their properties.

Tree structure

A network structure in tree topology is made up of combined star structures. In many mainframe systems, the central computer forms the root as the top node. It is connected to a star distributor, which is connected to other star distributors to which the host computers are connected. The tree structure is ordered hierarchically. The way to less important network components leads to the central computer via several distributor uplinks.

Advantages of the tree structure
Easily expandable with hierarchical order
The failure of an end node has no effect on the topology
Very large networks can be formed
Disadvantages of the tree structure
The failure of individual distribution nodes interrupts the data transport between the branches
The root distributor can become a bottleneck

Mesh structure

Each network node is connected to various other nodes by point-to-point connections. If all nodes are directly connected to one another, a fully meshed network is obtained. Almost all wide area networks work in a mesh topology. Data bottlenecks or connection disruptions can be avoided through intelligent routing processes.

Advantages of a mesh topology
High data transfer rates
Expandable as required
The failure of individual nodes is compensated for by routing procedures
Disadvantages of a mesh topology
A lot of connection cables between the nodes
If many nodes are networked, complete meshing cannot be achieved
The usual mesh topology requires a complicated routing procedure
Very high energy consumption, as all connection nodes are active computer systems