What Is a Token Ring? Understanding Local Area Networks

Developed by IBM in the late 1900s and standardized by IEEE 802.5, token rings provide an alternative to the more commonly used ethernet technology. Whether you are a network professional, learner, or simply someone interested in networking technologies, understanding token rings can enrich your understanding of network topologies and data transmission techniques.

What is a local area network (LAN)?

A local area network, commonly known as a LAN, is a network of interconnected devices confined to a specific geographic location, such as a building or residence. The size of a LAN varies depending on its use, ranging from a home setup with a single user to a corporate environment with thousands of users and devices. 

The distinguishing feature of a LAN is its limited scope: it serves devices in a localized area instead of a wide area network (WAN) or a metropolitan area network (MAN), both of which cover larger geographic zones. WANs and MANs often function as connective tissues that link multiple LANs.

What is a token ring network?

Token ring networks represent a particular type of LAN topology designed to manage data transmission in a more controlled manner. In this setup, data travels uni-directionally through a “ring” of interconnected nodes. The critical element here is the “token,” which is a unique digital signature that grants the authority to transmit data. When the token arrives at a particular station within the network, that station then sends its own data to the next place.

While token ring and ring topology might seem similar, they are fundamentally different. A token ring represents a networking protocol, while a ring topology characterizes a network layout where devices are interconnected circularly.

How token ring networks work

A token ring network, initially developed by IBM in the 1970s, operates on a ring topology and utilizes a token-passing mechanism to control data transmission between network nodes. Unlike ethernet, the token ring ensures a collision-free environment by allowing only one station to transmit simultaneously. 

When a station has data to send, it captures a circulating “free” token, converts it to a “busy” token, and then transmits a data frame. The frame travels the network until it reaches its destination and copies the data. The frame then completes its journey back to the originating station, confirming successful transmission, after which a new free token is released for other stations to use.

Token ring vs. Ethernet

When comparing token ring and ethernet technologies, several key distinctions arise. Unlike ethernet, in which all stations compete for network access through their bus topology, token rings ensure that every station gets a scheduled opportunity to transmit data. This makes the network more predictable and equitable, enhancing its reliability.

While Ethernet primarily uses unshielded twisted pair (UTP) wiring, token ring networks rely on shielded twisted pair (STP) wiring for more secure and robust transmissions. Ethernet also relies on carrier sense multiple access with collision detection (CSMA/CD) for data transmission, which can lead to occasional data collisions. Token ring employs a token-passing protocol, ensuring a more controlled and reliable data transmission.

Types of token rings

Token rings come in different variations, each offering its features and limitations. Specifically, Type 1 and Type 3 token rings are the most commonly used.

Type 1

Type 1 token rings can support a substantial network, accommodating 255 stations. They primarily use STP cabling with IBM-style Type 1 connectors, offering a robust and secure transmission medium.

Type 3

Type 3 token rings are more limited in scope, supporting up to 72 devices per network. These networks utilize UTP cabling, generally of Category (Cat) 3, 4, or 5 types, with Registered Jack 45 (RJ-45) connectors. 

Token ring hubs

In a token ring network, computers or stations connect to a centralized hub known as a multistation access unit (MAU or MSAU). The MAU is a conduit for data transmission in a logical ring pattern, even though the physical connections are star-shaped. 

An MAU may function as the central hub but operates differently from an ethernet hub. The network uses a unique token-passing mechanism, where a single data packet or token circulates among the stations, granting permission for data transmission. MAUs make adding or removing nodes from the system easier and act as protection if a node fails.

However, due to the dwindling prevalence of token ring networks, it is more common to encounter ethernet hubs or switches in contemporary settings today.

When are token rings used?

Network professionals may use token rings for media access control (MAC) protocols. Unlike point-to-point communication channels, LANs operate on shared media networks, which requires a sophisticated method for managing multiple devices’ access to the network. 

While contention-based methods like those in ethernet networks offer one approach, token rings employ a token-passing protocol for media access control. This token-based system facilitates orderly and collision-free data transmission, which professionals may find especially useful in environments requiring highly reliable or deterministic data transfer. 

Pros and cons of token rings

Token ring networks offer several advantages that contribute to their reliability and performance. One such feature is the priority system, which allows network administrators to designate high-priority stations that get more frequent access to the network. Each token frame contains priority fields, ensuring only stations with matching or higher priority levels can seize the token. Other advantages include:

• Eliminates collisions: The token-passing mechanism ensures that you don’t have data collisions in the network.

• Speed: Continual development has led to higher-speed versions of the token ring.

On the other hand, you may experience several disadvantages with token rings. Some of these include:

• System failures: Token rings are less reliable than some of their counterparts. Because of the ring topology, one point of failure can often affect the entire system. However, many professionals use MAUs to minimize this concern.

• Outdated: As more modern technologies emerge, token rings become less common, leading to fewer options for compatible hardware and software.

How to learn more about token rings

Learning about token ring networks can provide valuable insights into alternative networking topologies that prioritize controlled data transmission and reliability. Consider the following avenues to deepen your understanding:

• Educational courses: Many online platforms offer courses on network technologies, including token rings. 

• Books and academic journals: Various textbooks and articles explore the intricacies of token ring technology. 

• Industry publications: Websites dedicated to networking technologies often publish articles, reviews, and comparisons that can help you understand where token rings stand in the current technology landscape.

Getting started with Coursera

A type of local area network (LAN) topology, a token ring network transmits data in a single direction across a defined number of locations using a token.

You can learn more about network topologies with in-depth courses on Coursera offered by industry experts. IBM Data Topology by IBM is a highly-rated intermediate course designed to help you master data architecture, network concepts, and data management. Afterward, you may enroll in Peer-to-Peer Protocols and Local Area Networks course, also available on Coursera. Offered by the University of Colorado, this course focuses on medium access control protocols alongside local area network and wireless LAN technologies.