Why Still Use a Ring Network Topology?

Quick Definition: Ring topology is a network layout that emphasizes equal access to network resources in which all devices are arranged in a circular pattern, one connected to the next.

Ring network topology is still covered on various network-based certifications, such as CompTIA Network+, despite its classification as a legacy topology. During its heyday, it did combat some serious limitations with bus topology and star topology. Let's dive into the inner workings of ring topology, and how it benefited early computer networks.

What is a Ring Network Topology?

A ring topology is a topology that creates a circle such that each node is connected to two other nodes. It is easiest to visualize this as a circle or ring. In a basic ring topology, data typically travels in one direction. The data goes from node to node until reaching its destination.

Early on, there were few implementations of the ring topology. IBM's Token Ring was the earliest of them and allowed for a single ring over copper. Let’s briefly go over tokens and how they play an integral role in ring topology.

What are Tokens?

Tokens are designated packets on a network used to control data flow and provide the possessor with the ability to transmit data. It circulates the network in a deterministic manner, providing each recipient with a chance to transmit data. Once the node is finished executing its task, or if it has no tasks to complete, the token is passed on.

In many ways, it is like a therapy session “talking stick”. Only the individual with the talking stick is allowed to share stories, and everyone else must listen until the baton is passed to another group member.

Ring Topology Diagram

Ring Topology Advantages

Though you probably won’t see a ring topology in a modern network, there are still several advantages to ring topologies. In ring network topologies, each node gets equal time share. Ring topologies make sure all the computers don’t try to talk at the same time, and they also eliminate collisions. Here are several advantages of ring topology:

Tokens Provide Equal Time Share Access 

This helps to avoid the noisy neighbor problem where one node tends to take the majority of the time and bandwidth on the network. Tokens are used to control access to the network. Only nodes that have a token are allowed to transmit data. This mitigates the possibility for data collisions and preserves necessary bandwidth to execute specified tasks.

Linear Data Transmission Prevents Collisions

It was important in early topologies to avoid collisions. The early competitor to the ring topology was the busy topology which had a high affinity for collisions. The lack of collisions leads to more time sending actual data instead of transmissions being halted to retries and avoid further collisions.

Ring Topology Can Be High Performant

As long as the network is small to medium size, ring topology can act as a speedy solution. A well-implemented ring topology will have a predictable and constant data rate. The data is not at risk of reflection like in bus topology, so the risk of data loss is greatly reduced. Additionally, the combinations of tokens and single-direction data transmission eliminate the possibility of data collision. Since data will never have to be re-sent, it will boost the network’s performance. 

Ring Topology Disadvantages

One of the downsides to a ring topology is that a break in the ring could render the entire ring useless. Traffic also flowed in a singular direction. This was mitigated by dual ring networks, but that increased the cost. If two separate nodes had a break in the ring, the same problem existed as a singular break in a one ring topology. The issue at hand was that a break in the network could impact the functionality of it.

Difficult to Troubleshoot:

While this may not seem like an issue, a failed network card in one of the machines could lead to the entire network segment being brought down. Often, it is difficult to discern where exactly the disconnect occurred. This can potentially cause hours of troubleshooting to discover which NIC broke or which wire snapped.

On the flip side, one of the best ways to mitigate this disadvantage is to implement a dual ring topology. In a nutshell, dual ring topology adds an additional ring to the topology, thus increasing its fault tolerance and redundancy. If one ring is severed, the traffic will route on the secondary ring.

Ring Topology Can Be Expensive

Signal degradation due to wire length is an inherent issue with ring topology. It can be overcome by leveraging FDDI (Fiber Distributed Data Interface). FDDI was a viable, pre-Ethernet option for ring topology, which was considered a pricey technology. It was a specific type of LAN used to transmit data over fiber optic cables. It has since been superseded by Ethernet. 

The cost of a ring topology can be reduced by using Cat5 cables to connect various nodes in the network. Unfortunately, this also requires each node to be conveniently accessible to the nodes next to it. This requirement can incur costs in and of itself. For example, the nearest node could be in another adjacent room, which would require additional drilling into the wall to make each node readily accessible to each other. Careful planning is required when implementing any topology, and costs can be reduced before they are incurred by optimizing your space for the specific topology you wish to implement.

Ring Topology Can Be Difficult to Configure:

This is likely the main reason it has become mostly extinct. Running a single or dual ring required quite a bit of cabling. It can be difficult to architect the wiring necessary to facilitate this type of topology.

Ring Topology is Not Scalable

Unfortunately, adding additional nodes to a ring topology can be a complex and time-consuming process. That is because you have to break the ring, connect your node, and then reconnect the ring. This can become a tricky process as more nodes are added to the network. Also, if tokens are getting passed, each node added means each node will have to wait that much longer for a token. This will inherently produce network latency.

What’s Happening with Ring Topology?

Ring topology is an important part of networking history. It solved a few issues that bus topology and star topology had at the time, such as collisions and the ability to prevent a "noisy neighbor" from stealing all the bandwidth on the network. At some point, this topology may make a comeback. As the saying goes, "What is old is new, and what is new is old."

Final Thoughts

While the ring topology may not be in use, it is always best to understand historical architectures to learn from them and their ideal use cases. With the emergence of new networking technologies and scenarios, there may be a need to revive older technologies. On the other hand, use cases where ring topologies are a poor choice need to be understood so they are not resurrected when they should not be.