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Ring network

A ring network, also known as ring topology, is a network configuration in which each device or node is connected to exactly two neighboring nodes, forming a closed loop where data packets travel sequentially in a unidirectional or bidirectional circular path from one node to the next until reaching their destination.^[1] This topology ensures that data transmission follows a logical ring structure, often implemented physically as a star-wired layout for easier management, and relies on protocols like token passing to regulate access and prevent collisions.^[2] Common implementations include local area networks (LANs) and metropolitan area networks (MANs), with data rates varying from 4 Mbps in early systems to over 100 Mbps in fiber-optic variants.^[3] The origins of ring networks trace back to the 1970s, when researchers explored deterministic access methods to address limitations in shared-medium networks like Ethernet.^[3] IBM played a pivotal role in popularizing the topology through its Token Ring network, developed in the late 1970s and commercially released in 1985, which was later standardized as IEEE 802.5 with initial speeds of 4 Mbps on shielded twisted-pair cabling.^[2] This system used a 3-byte token frame that circulated the ring, granting transmission rights to the possessing node for predictable performance.^[3] In the 1980s, the Fiber Distributed Data Interface (FDDI), an ANSI standard, extended ring concepts to high-speed fiber-optic LANs at 100 Mbps, employing dual counter-rotating rings for fault tolerance and supporting up to 500 nodes over a total distance of 100 km.^[4] Similarly, Synchronous Optical Networking (SONET), standardized by ANSI following the 1984 AT&T divestiture, adopted ring topologies for telecommunications backbones, enabling high-capacity, self-healing fiber rings at rates from 51.84 Mbps (OC-1) upward to provide resilient wide-area connectivity.^[5] Ring networks offer several key advantages, including collision-free operation via token mechanisms, which ensures fair and deterministic bandwidth allocation even under heavy load, making them suitable for time-sensitive applications.^[2] They are also relatively straightforward to install and troubleshoot, as cable faults can be isolated by monitoring the loop.^[1] However, a major drawback is their vulnerability to single points of failure: a break in the ring or node malfunction can halt the entire network unless mitigated by dual-ring designs like those in FDDI or SONET.^[2] Adding or removing nodes often requires network reconfiguration, disrupting operations, which contributed to the decline of pure ring LANs in favor of more flexible topologies like Ethernet by the 1990s.^[1] Despite this, ring principles persist in modern resilient systems, such as metro Ethernet rings and optical transport networks.^[5]

Fundamentals

Definition and Topology

A ring network is a network topology in which each node connects to exactly two other nodes, forming a closed loop or circular data path that enables sequential transmission of data around the ring. In this configuration, data packets travel from one node to the next in a predetermined direction until they reach their intended destination, ensuring that every node has a direct path to transmit and receive information without requiring a central controller. This topology is characterized by its simplicity and efficiency in distributed environments, where nodes function as both transmitters and repeaters for incoming signals. The basic structure of a ring network can be unidirectional, where data flows in a single direction (clockwise or counterclockwise), or bidirectional, allowing traffic in both directions through separate paths or dual connections. Each node typically includes a receiver for incoming data and a transmitter for outgoing data, with the signal being regenerated at each hop to maintain integrity over the loop. Visually, a ring network is often represented as a circle of nodes linked by lines, with arrows indicating the direction of data flow; for instance, in a unidirectional ring, arrows point consistently around the perimeter, illustrating the sequential progression of packets from source to destination. Unlike bus topologies, which use a single shared communication line prone to collisions, or star topologies that rely on a central hub for connectivity, ring networks distribute control evenly without a single point of failure in the core structure. Mesh topologies, by contrast, provide multiple interconnections between nodes for redundancy, whereas rings maintain a fixed, loop-based linkage that prioritizes ordered access. One common method for managing access in such networks involves token passing, where a control token circulates to authorize transmission, though detailed protocols are covered elsewhere.

Historical Development

The concept of ring networks originated in the late 1960s through research on looped communication systems aimed at enhancing reliability in distributed computing. At Bell Labs, researchers John Newhall and David Farmer explored ring-like structures for interconnecting computers, presenting ideas at conferences that influenced subsequent designs.^[6] In 1970, David Farber at the University of California, Irvine, drew inspiration from this work to develop a token-passing ring network as part of a National Science Foundation-funded project, creating an early prototype using minicomputers connected at 2.5 Mbps over twisted-pair wire; this Distributed Computer System (DCS) demonstrated decentralized message passing and became operational by late 1973.^[6] During the 1970s, IBM advanced ring network technology, focusing on token ring protocols to enable efficient local area networking. IBM's research, led by engineers including Werner Bux and Hans Müller, refined the token-passing mechanism for collision-free data transmission, culminating in prototypes tested internally by the decade's end.^[7] In the early 1980s, IBM submitted its token ring design to the IEEE, contributing to the formation of the 802.5 working group in 1982 as part of the broader IEEE 802 LAN standards effort initiated in 1980.^[8] The IEEE 802.5 standard for Token Ring was first published in 1985, specifying speeds of 4 Mbps and later 16 Mbps over shielded twisted-pair cabling, and was fully ratified in 1989.^[9] Parallel to Token Ring's evolution, the Fiber Distributed Data Interface (FDDI) emerged in the 1980s as an optical ring standard for higher-speed backbones. Developed by the ANSI X3T9.5 committee starting in 1980, FDDI used dual counter-rotating fiber rings operating at 100 Mbps, with the initial standard published in 1986 and completed by 1994; it addressed metropolitan area networking needs with improved fault tolerance.^[4] IBM commercially released Token Ring in 1985, including hardware like the IBM Token-Ring PC Adapter, driving widespread adoption in enterprise environments during the mid-1980s. By the 1990s, ring networks began declining in favor of Ethernet due to the latter's lower cost, simpler implementation, and rapid speed advancements, such as Fast Ethernet at 100 Mbps in 1995.^[10] Formal support for Token Ring ended with the disbanding of the IEEE 802.5 working group in 2008, though ring topologies persisted in niche applications like industrial control systems for their deterministic performance.^[11] Dual-ring redundancy, as in FDDI, briefly extended ring viability for fault-tolerant designs but could not compete with Ethernet's scalability.^[4]

Operational Mechanisms

Data Flow and Transmission

In a unidirectional ring network, data frames propagate continuously in a single direction—typically clockwise or counterclockwise—forming a closed loop where each node serves as a repeater for the signal. Every frame passes through all nodes sequentially, enabling efficient broadcast-like dissemination while maintaining ordered access. This topology ensures that the signal latency is predictable, as the total propagation delay is bounded by the ring's circumference.^[12] The transmission process begins when a source node seizes the opportunity to insert a frame, often regulated by a token-passing mechanism to prevent contention. The node converts the circulating token into a data frame by appending its payload, destination address, and control information, then releases it onto the ring. As the frame circulates, intermediate nodes read the header to check the destination address; if matched, the receiving node copies the data while allowing the frame to pass unchanged. Upon returning to the source after a full loop, the node strips the frame from the ring to free bandwidth, ensuring no residual traffic accumulates. This copy-and-forward approach minimizes duplication while guaranteeing delivery in a fault-free environment.^[12]^[13] Signal propagation in classic ring implementations relies on encoding schemes that embed clock synchronization within the data stream for reliable bit recovery. For instance, early systems like IEEE 802.5 Token Ring employ differential Manchester encoding, in which a transition occurs at the beginning of every bit period, with an additional transition in the middle for a 0 and none for a 1, using voltage levels around ±3V for self-clocking and polarity independence. This self-clocking method, operating at speeds like 4 Mbps or 16 Mbps, facilitates precise timing extraction without dedicated clock lines and includes special delimiter symbols (e.g., start and end delimiters) formed by encoding violations to demarcate frame boundaries unambiguously. At the bit level, frames adhere to a structured format: a 1-byte start delimiter signals initiation, followed by access control and frame control bytes, 6-byte source and destination addresses, variable-length data (up to 18,000 bytes in high-speed variants), and control fields for status.^[13]^[12] Basic error detection occurs at the transmission level through a 32-bit cyclic redundancy check (CRC) appended as the frame check sequence (FCS), computed as a polynomial over the frame's address, control, and data fields. Each receiving node recalculates the CRC upon frame arrival; a mismatch indicates corruption from noise or attenuation, prompting the node to set error-indicating bits in the frame status field and discard the payload. This mechanism provides robust integrity verification without forward error correction, relying instead on higher-layer retransmission if needed.^[13]^[12]

Node Connectivity and Failure Handling

In ring networks, each node acts as an active repeater, regenerating and amplifying incoming signals to prevent degradation and ensure reliable propagation around the loop. This active repeating is essential for maintaining signal integrity over distances, distinguishing ring topologies from passive configurations where nodes do not actively process signals. In the IEEE 802.5 Token Ring standard, one active node is elected as the active monitor through a contention process using MAC addresses, responsible for timing synchronization, token generation, and fault detection, while all others operate as standby monitors ready to assume the role if the active monitor fails.^[12]^[7]^[14] Physical connectivity between nodes relies on point-to-point links forming the closed loop, commonly using shielded twisted-pair cables (such as IBM Type 1 or Type 3) for Token Ring implementations supporting speeds up to 16 Mbps over distances of about 100 meters per segment. Fiber optic cables are employed in higher-speed variants like Fiber Distributed Data Interface (FDDI), enabling transmission up to 100 Mbps over several kilometers with lower attenuation. Node insertion follows a structured multi-phase procedure to avoid disrupting the ring: a new node first listens to the network, claims participation by inserting a special frame, calibrates timing, and fully joins only after verifying ring stability, while removal involves signaling neighbors to close the gap, often via multistation access units (MAUs) that electrically isolate the node.^[7]^[14] Failure modes in single-ring networks primarily involve single points of disruption, such as a cable break or node crash, which can partition the ring and halt data circulation for all nodes. Detection occurs through signal loss monitoring, where the absence of expected tokens or frames triggers alerts, or via beaconing in Token Ring, where a affected node broadcasts beacon frames to identify the failure domain spanning from the sender to its nearest active neighbor.^[12]^[7] Handling strategies emphasize automatic reconfiguration to restore connectivity with minimal downtime, typically within milliseconds. In Token Ring, MAUs use electrical bypass relays to isolate and shunt failed nodes, allowing the ring to reform around the fault, while the active monitor issues a ring purge to clear erroneous frames and regenerate a token. Fiber-based rings like FDDI employ optical bypass switches that optically loop signals past failed nodes or links, preventing light loss and enabling rapid isolation without electrical intervention. Dual-ring designs enhance resilience by dedicating a secondary ring for counter-rotating traffic, which can assume primary duties upon primary failure detection.^[12]^[14]

Variants and Implementations

Single-Ring Configurations

A single-ring configuration forms the foundational topology of a ring network, consisting of a closed-loop circuit that interconnects 2 to hundreds of nodes in a unidirectional manner, with data circulating sequentially through each station until it returns to the source. This setup was prominently featured in early local area networks (LANs), such as IBM's Token Ring, which operated at speeds of 4 Mbps or 16 Mbps to support shared access among connected devices.^[7]^[15] Key components include network interface cards (NICs), also known as adapters, installed in each node to manage frame insertion, removal, and error checking, ensuring compliance with the ring's protocol. Connections are typically handled by multistation access units (MAUs), which provide a physical star-wired interface while preserving the logical ring, allowing up to 260 devices per ring and enabling easy node addition or removal without disrupting the loop.^[15]^[7] Performance in single-ring designs is constrained by increasing latency with node count, as every frame must propagate through all stations, leading to cumulative delays; the total ring latency is given by

\tau = N \cdot \delta + \frac{L}{v},

where N is the number of nodes, \delta is the per-node processing delay (often equivalent to the bit transmission time), L is the total cable length, and v is the signal propagation velocity. This linear scaling limits scalability, with practical rings supporting up to 260 nodes but experiencing noticeable slowdowns beyond dozens of active stations under load.^[13]^[16] Such configurations found primary application in small-scale office networks during the 1980s and 1990s, where they efficiently handled moderate data traffic for tasks like file sharing and printing in environments with 10 to 50 workstations, prior to the dominance of Ethernet alternatives.^[7]^[17]

Dual-Ring and Redundant Designs

In dual-ring topologies, networks incorporate two counter-rotating rings—a primary ring for standard data transmission in one direction and a secondary ring serving as a backup that transmits in the opposite direction—to provide inherent redundancy and fault tolerance. This architecture allows the network to maintain connectivity even if one path is compromised, with data typically flowing clockwise on the primary ring and counterclockwise on the secondary. A prominent example is the Fiber Distributed Data Interface (FDDI), a 100 Mbps token-passing local area network standard that uses fiber-optic cabling to support up to 500 nodes over distances of up to 200 km when wrapped.^[18]^[19] Redundancy mechanisms in dual-ring designs enable automatic reconfiguration upon detecting failures, such as cable breaks or node outages, by "wrapping" the secondary ring to form a single, continuous loop from the primary ring. In FDDI, stations equipped with optical bypass switches automatically isolate faulty components, preventing ring segmentation and allowing the network to self-heal rapidly through this wrapping process, which minimizes downtime and supports continuous operation. This fault-tolerant approach contrasts with single-ring vulnerabilities by ensuring traffic rerouting without manual intervention, though multiple simultaneous failures may segment the ring into isolated loops.^[18]^[19] Logical ring implementations extend redundancy to software-defined configurations over non-ring physical media, creating virtual rings that emulate ring behavior for enhanced reliability. For instance, in metro Ethernet networks, standards like ITU-T G.8032 Ethernet Ring Protection Switching (ERPS) form logical rings across Ethernet infrastructure, enabling sub-50 ms protection switching for traffic restoration in ring-like topologies without requiring a physical loop. These virtual designs leverage protocols to block redundant paths under normal conditions and activate them during faults, providing scalable redundancy in diverse physical layouts.^[20]^[21] Telecommunications enhancements build on dual-ring principles through Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) rings, which employ Add-Drop Multiplexers (ADMs) to dynamically route traffic by adding or dropping signals at nodes without interrupting the overall ring flow. ADMs in these systems multiplex lower-speed signals into high-capacity optical carriers (e.g., OC-3 at 155 Mbps or higher), supporting bidirectional protection paths that switch in under 50 ms to restore services after failures, making them ideal for carrier-grade metro and wide-area networks. This architecture facilitates efficient bandwidth allocation and self-healing, with traffic automatically rerouted along the protection ring.^[22]^[23]

Access and Control Methods

Token-Passing Protocols

In token-passing protocols for ring networks, a special control frame known as a token circulates continuously around the logical ring, granting the possessing node exclusive rights to transmit data and thereby preventing collisions inherent in shared-medium access methods.^[24] This deterministic approach contrasts briefly with probabilistic methods like CSMA/CD used in non-ring topologies, ensuring predictable access without contention.^[25] The IEEE 802.5 standard defines the Token Ring protocol, which employs two primary token types: a free token, available for seizure by any node, and a busy token, created when a node converts the free token into a data frame header to initiate transmission.^[26] To support differentiated access, the protocol incorporates a priority mechanism with eight levels (0 through 7), where higher-priority nodes can reserve the token via fields in the frame format, allowing them to preempt lower-priority transmissions upon token reacquisition.^[24] The operational cycle begins with the token's rotation around the ring, where each node checks for data to send; if none, it forwards the token, completing a full rotation in a time determined by ring latency and node count.^[25] Fair access is enforced through the Token Holding Timer (THT), which limits a node's token possession to a configurable maximum—typically 10 milliseconds—to prevent monopolization and guarantee bounded response times for all stations.^[24] An extension to the base protocol, Early Token Release, enhances efficiency under high-load conditions by allowing a transmitting node to immediately release a new free token after dispatching its frame, rather than waiting for the frame to return, thereby enabling multiple concurrent transmissions on the ring.^[26] This optional feature, supported in IEEE 802.5 implementations, reduces idle time and improves throughput without altering the core token-passing logic.^[25]

Alternative Access Protocols

In ring networks, alternatives to token-passing protocols for managing access and preventing collisions include slotted and demand-based methods, which aim to provide efficient medium utilization without the overhead of circulating a single token. These approaches were explored in early experimental systems to address limitations in deterministic access under varying loads.^[27] The slotted ring protocol divides the circulating bit stream into fixed-size slots that continuously rotate around the ring, allowing nodes to insert data packets into empty slots as they pass by. Each slot includes header information to indicate availability and destination, enabling nodes to seize an empty slot for transmission while stripping their own packets upon return to maintain ring hygiene. This method, inspired by reservation techniques in shared media, was analyzed in performance models for local area networks, showing effective handling of multiple simultaneous transmissions through the multiplicity of slots. Early implementations, such as those in the Cambridge Ring variants, demonstrated its suitability for integrated voice and data environments by reducing idle time on the medium.^[28]^[29] Demand-based access protocols, such as register insertion, enable nodes to transmit on demand by buffering packets locally until an opportunity arises on the ring. In this scheme, each node maintains a register or buffer; when no data is present on the ring (a gap detected), the node inserts its packet directly into the stream, effectively delaying the downstream traffic temporarily to accommodate the insertion. Upon the packet's return, the node removes it and restores the original stream from the buffer. This approach was developed for high-speed optical fiber rings operating up to 100 Mbit/s, providing fair access without fixed slots or tokens. Prototypes highlighted its use in next-generation LANs, where nodes signal transmission intent implicitly through gap detection.^[30]^[31] Compared to token-passing, which remains the dominant method for deterministic access in ring networks, slotted and register-insertion protocols exhibit lower overhead at low to medium loads due to the absence of token circulation delays. Slotted rings achieve higher throughput with multiple concurrent packets, particularly for short messages, while register insertion offers superior average response times at high loads—up to 60% improvement in throughput and halved delays through partitioning schemes—though both may introduce contention delays under heavy, bursty traffic. These alternatives were particularly advantageous in experimental high-speed prototypes but saw limited commercial adoption relative to token-based standards.^[27]^[31]

Performance Evaluation

Key Advantages

Ring networks provide deterministic performance through their ordered access mechanisms, such as token-passing protocols, which ensure predictable latency for data transmission. In these topologies, the maximum wait time for a node to transmit is bounded by the time required for the token to traverse the entire ring circumference, allowing for reliable scheduling in time-sensitive applications.^[32] A key benefit is the equal access granted to all nodes, independent of their physical position in the network. Unlike bus topologies where position can affect signal propagation, ring designs allocate a fair share of bandwidth to each node, preventing distance-based degradation and promoting equitable resource utilization.^[33] The simplicity of wiring in ring topologies reduces installation complexity compared to fully meshed networks, requiring only two connections per node to form a closed loop, which uses fewer cables overall. In star-wired implementations common to networks like Token Ring, this approach facilitates expansion with minimal disruption by connecting new nodes via access units without breaking the logical ring.^[32] In redundant designs, such as dual-ring configurations, ring networks enable effective fault isolation, confining the impact of a failure to specific segments while allowing traffic to reroute around affected areas. This containment ensures that a single link or node failure does not propagate across the entire network, enhancing overall resilience.

Primary Disadvantages

Ring networks are particularly vulnerable to single points of failure, where a break in the cable or malfunction of a single node can disrupt the entire loop, halting data transmission across all connected devices unless redundancy measures are implemented.^[34] This susceptibility arises because data circulates unidirectionally through every node, making the topology inherently fragile without additional safeguards.^[35] Scalability in ring networks is limited by the linear increase in propagation delay as the number of nodes grows, since signals must traverse all intermediate nodes to reach their destination, leading to inefficiencies in larger configurations.^[36] For instance, in a network with many nodes operating at standard speeds like 16 Mbps, the cumulative latency can become substantial, on the order of a few milliseconds for the full ring circulation, which may degrade overall performance under heavy load.^[37] Maintenance of ring networks presents significant challenges, as diagnosing faults requires tracing the signal path along the entire loop, which can be time-consuming and complex in distributed setups.^[38] Furthermore, in pure ring configurations, inserting or removing a node typically disrupts the whole network, necessitating reconfiguration to restore connectivity, though star-wired variants mitigate this.^[37] Cost factors also hinder widespread adoption of ring networks, with higher expenses for specialized network interface cards (NICs) and extensive cabling requirements compared to more flexible topologies like Ethernet, especially in expansive deployments.^[39] These elevated implementation and upkeep costs make ring networks less economical for large-scale environments. Dual-ring designs can mitigate some failure risks but add further complexity and expense.^[40]

Applications and Evolution

Traditional Deployments

Ring networks found significant application in local area networks (LANs) during the 1980s and 1990s, particularly through IBM's Token Ring technology, which was widely deployed in corporate offices for reliable data sharing among workstations and servers. Introduced commercially in 1985, Token Ring enabled deterministic access via token passing, making it suitable for environments requiring predictable performance, such as business computing in large organizations. Networks could support up to 260 nodes per ring using shielded twisted-pair cabling, allowing scalability for office-wide connectivity without the collision issues common in bus topologies.^[41] It saw widespread adoption in the late 1980s and early 1990s as IBM integrated it with its Systems Network Architecture (SNA) for mainframe connectivity, though it began to decline in the mid-1990s with the rise of Ethernet.^[42] In industrial settings, ring networks based on token-passing protocols were utilized in manufacturing control systems to ensure fault-tolerant communication between programmable logic controllers (PLCs), sensors, and supervisory computers. These deployments emphasized the topology's ability to maintain operation despite node failures, critical for real-time process monitoring and automation in factories during the 1980s. For instance, IBM Token Ring variants were adapted for linking industrial controllers, providing low-latency data exchange in environments like assembly lines.^[43] Similar token-passing mechanisms influenced protocols like the Manufacturing Automation Protocol (MAP), which, while primarily bus-based, drew on ring-inspired concepts for orderly access in plant-wide networks.^[44] Telecommunications applications included early metropolitan area networks (MANs) leveraging Fiber Distributed Data Interface (FDDI), a 100 Mbps ring standard developed in the late 1980s for high-speed backbone connectivity across campuses. FDDI's dual-ring redundancy supported fault tolerance, making it ideal for linking buildings in university or corporate campuses, where it served as an upgrade from slower Ethernet backbones. Deployments began in the early 1990s, connecting distributed computing resources over fiber optics up to 200 km in circumference.^[45] Notable case studies highlight ring networks' experimental roots, such as the Massachusetts Institute of Technology's (MIT) Laboratory for Computer Science prototypes in the late 1970s and early 1980s. MIT operated a 1 Mbit/s distributed control ring with eight nodes starting around 1979, evolving to a 10 Mbit/s token ring by 1984 to test traffic patterns and initialization protocols. These efforts influenced commercial designs and demonstrated ring viability for research environments, contributing to adoption trends in the mid-1980s across academia and industry.^[46]^[47]

Contemporary and Legacy Uses

Despite the dominance of Ethernet-based networks, Token Ring persists in legacy IBM mainframe environments, particularly for Systems Network Architecture (SNA) applications in z/OS Communications Server, where it supports backward compatibility for older enterprise systems. Emulation of Token Ring is available in virtual machine platforms like z/VM, allowing guest operating systems to utilize virtual Token Ring adapters for maintaining compatibility with historical workloads in emulated environments. In modern industrial settings, ring topologies remain relevant for Industrial Internet of Things (IIoT) and Supervisory Control and Data Acquisition (SCADA) systems, providing deterministic control through redundancy mechanisms. For instance, PROFIBUS networks can be configured as redundant optical rings using Optical Link Modules (OLMs), enabling fault-tolerant communication in process automation where predictable latency is critical for safety and reliability.^[48] These configurations support real-time fieldbus communications in manufacturing and energy sectors, ensuring minimal downtime via automatic failover in ring structures.^[49] Optical ring networks continue to underpin telecommunications backbones, with Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) rings providing self-healing capabilities for high-availability transport in regional and national infrastructures as of 2025.^[50] These legacy systems are evolving toward Dense Wavelength Division Multiplexing (DWDM) rings, which increase capacity by multiplexing multiple wavelengths on a single fiber, often in hybrid setups integrating Ethernet services for metro aggregation.^[51] Such DWDM ring architectures facilitate seamless interoperability between optical transport and packet-based Ethernet, supporting diverse traffic in carrier networks.^[52] Emerging applications leverage virtual ring topologies within Software-Defined Networking (SDN) frameworks for data centers, enabling dynamic reconfiguration of logical rings over physical underlays to optimize traffic flow and resilience.^[53] In SDN environments, these virtual rings allow centralized control for load balancing and fault recovery, adapting ring structures virtually without hardware changes, which is particularly useful for scalable cloud interconnects.^[54]

Common Misconceptions

Topology Confusions

One common confusion arises between ring and bus topologies, where the ring is often mistakenly viewed as a variant of the bus due to superficial similarities in shared media access. In reality, a ring topology forms a closed loop in which each node connects directly to exactly two others, enabling unidirectional data flow without the need for terminators at endpoints, as signals circulate continuously around the circle.^[55] In contrast, a bus topology employs a linear backbone cable to which all devices connect in parallel, requiring terminators at both ends to absorb signals and prevent reflections, with data propagating bidirectionally along the shared line.^[55] This structural difference means that a single cable failure in a bus severs the network into isolated segments, whereas in a ring, the loop maintains connectivity unless a node fails.^[56] Another frequent mix-up involves assuming all ring networks require physical wiring in a literal circular loop, overlooking the distinction between physical and logical topologies. The physical topology describes the actual arrangement of cables and devices, while the logical topology defines how data traverses the network regardless of cabling.^[57] A key example is IBM's Token Ring network, which employs a star-wired physical topology—devices connect via dedicated links to a central multistation access unit (MAU)—but operates as a logical ring, where data and tokens pass sequentially from one station to the next in a virtual circle managed by the protocol.^[58] This design allows for easier fault isolation and cabling flexibility, countering the misconception that rings demand direct point-to-point loops in hardware.^[59] Ring topologies are also sometimes conflated with daisy-chain configurations, particularly in serial interconnections, leading to errors in understanding redundancy and failure modes. A daisy chain links devices in a sequential linear fashion without closing the circuit, resembling an open-ended bus where data must traverse each intermediate node to reach distant ones, and a break anywhere disrupts downstream communication.^[38] In contrast, a true ring closes the daisy chain into a loop, providing an alternate path for data to circumvent a single failure via the opposite direction, though it requires protocol support to reconfigure dynamically.^[60] Without this loop closure, a daisy chain lacks the inherent redundancy of a ring, making it unsuitable for high-availability scenarios.^[56] Diagrammatic representations often exacerbate these confusions, especially with star-wired implementations like Token Ring, which visually resemble star topologies at first glance. In such diagrams, the central hub and radial connections mimic a star's centralized structure, leading observers to overlook the internal ring logic where the MAU internally wires ports into a looped path for token circulation.^[59] This external similarity can mislead in network planning, as a true star relies on the hub for all switching without sequential passing, whereas the star-wired ring preserves the token-passing discipline of a pure ring.^[58] Proper labeling and internal schematics are essential to distinguish these, avoiding deployment errors in hybrid environments.^[56]

Performance Myths

One common misconception about ring networks is that they offer infinite scalability, allowing seamless expansion to thousands of nodes without performance degradation. In reality, the latency in ring networks grows linearly with the number of nodes, O(N), due to the ring latency—the time required for a token or data frame to propagate around the entire ring—which increases proportionally as more stations are added, making large-scale deployments inefficient for high-throughput applications. Another overstated claim concerns the reliability of ring networks, particularly those employing dual-ring configurations, which are often portrayed as completely fault-tolerant. While dual rings provide redundancy by allowing traffic to reroute around a single failure in one direction, they are not immune to multiple simultaneous failures; for instance, two breaks in the ring can segment it into isolated sub-rings, preventing communication between affected segments and causing network partitioning.^[18] Configuration errors, such as improper station initialization or mismatched ring speeds, can also disrupt the entire network, underscoring that dual-ring setups enhance but do not eliminate vulnerability to cascading issues.^[12] Misconceptions about speed frequently arise when comparing ring networks like Token Ring to Ethernet, with some asserting that Token Ring is inherently slower. Token Ring operated at 4 Mbps or 16 Mbps, which was competitive with 10 Mbps Ethernet in the 1980s, often delivering superior effective throughput under heavy loads due to its collision-free token-passing mechanism rather than Ethernet's contention-based access.^[14] However, as Ethernet evolved to 100 Mbps and beyond in the 1990s, Token Ring's fixed speeds and higher implementation costs led to its decline, not an intrinsic speed deficit.^[61] The notion that ring networks provide inherent determinism suitable for all real-time applications is also exaggerated, as they offer predictable access delays but fall short for hard real-time systems without specialized extensions. Standard Token Ring protocols guarantee bounded latency through token circulation, ensuring fair access akin to its advantages in load balancing, yet the worst-case delay scales with ring size and traffic, necessitating advanced scheduling algorithms to meet stringent deadlines in time-critical environments.

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Ethernet ring protection switching (ERPS) helps to prevent fatal loops from disrupting a network. ERPS is similar to spanning-tree protocols, but ERPS is more ...Ethernet Ring Protection... · Ring Node States · Raps Message Blocking And...Missing: repeater | Show results with:repeater
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Ring Network - an overview | ScienceDirect Topics
A ring network consists of devices connected in a closed loop, where each node has one connection to its predecessor and one to its successor, forming a circle ...
[22]
A Brief Overview of SONET Technology - Cisco
Jun 14, 2005 · Multiple lower-level SONET signals can be mixed together to form higher-level SONET signals. An Add/Drop Multiplexer (ADM) is an example of LTE.
[23]
Add-Drop-Multiplexer - an overview | ScienceDirect Topics
The rings are implemented using SONET/SDH add/drop multiplexers (ADMs), which we studied in Section 6.1 . These ADMs selectively drop and add traffic from/to ...
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[PDF] Token Ring/IEEE 802.5
The related IEEE 802.5 specification is almost identical to and completely compatible with IBM's Token Ring network. In fact, the IEEE 802.5 specification was.Missing: free busy
[25]
[PDF] Token Ring - Network Protocols Lab
– Bus: IEEE 802.4. – Ring: IEEE 802.5,. Fiber Distributed Data Interface (FDDI). • Token Holding Time (THT) = maximum time a station may hold a token. Ring ...Missing: protocol details free busy
[26]
IEEE 802.5 Token Ring
IEEE 802.5 Token Ring. The Token Ring network was originally developed by IBM in the 1970s. It is still IBM's primary local area network (LAN) technology ...<|separator|>
[27]
The slotted ring vs. the token-controlled ring: A comparative evaluation
Abstract: In this paper we analyze the performance of two predominant ring architectures: the slotted ring and the token-controlled ring.Missing: comparison | Show results with:comparison
[28]
Modeling a Slotted Ring Local Area Network - IEEE Computer Society
Models for local area networks of the slotted ring style of architecture are developed and evaluated. The hardware protocol is modeled using a BCMP network.
[29]
A performance analysis of the slotted ring protocol for a voice/data ...
Abstract. A performance analysis of the slotted ring protocol for a voice/data integrated network environment is presented. At each node two types of packet ...
[30]
High-speed optical-fibre ring network with a register insertion access ...
The ring is to operate at speeds up to 100 Mbits−1 and employs the register-insertion technique as the access protocol. Other possible protocols are also ...
[31]
Register-insertion: A protocol for the next generation of ring local ...
The register-insertion ring is known for its high maximum throughput as well as its low average response time at medium and high loads.
[32]
Why a ring? - ACM Digital Library
This approach reduces the wiring cost that one might anticipate in a star topology. ... II., and Pogran, K., "A Star--Shaped. Ring Network with Iligh ...
[33]
Basic Knowledge of Network Systems - SpringerLink
Oct 21, 2022 · The advantages of the ring topology include: simple structure, assigning equal status to all workstations in the system; easy networking, where ...
[34]
[PDF] Token Ring
– One approach: change one bit in token which transforms it into a “start-of-frame sequence” and appends frame for transmission. – Second approach: station ...
[35]
[PDF] N92-14219
Basic ring topology, shown in Figure 3, has the advan- tage of being a group of point-to-point links, with each node being an active repeater; thus it requires ...
[36]
[PDF] Performance Modeling and Evaluation of Topologies for Low ... - DTIC
However, since a message from one node in a ring must traverse every other node in that ring, this topology becomes inefficient as the number of nodes increases ...
[37]
The Impact of Network Topology on Data Transmission Speedand ...
May 24, 2024 · Simple to expand. Disadvantages of Ring Topology. Removing and adding causes network disruption. Troubleshooting poses a challenge. Data ...
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Network Topology Types: Complete Overview - NAKIVO
May 13, 2021 · The ring topology is faster than the bus topology. The coaxial cable and connectors used to install a network of the ring topology are the same ...
[39]
Token Ring Network - an overview | ScienceDirect Topics
The media access unit (MAU), also known as the multistation access unit (MSAU), is the Token Ring equivalent of a hub or switch on the Ethernet networks. All ...
[40]
[PDF] Module 4: Local Area Networks (LANs) - Jackson State University
The ring topology is susceptible to failure with break in the cable; but, it could be made more fault tolerant with the use of a backup ring. – Ring topologies ...
[41]
https://ieeexplore.ieee.org/document/6434299
[42]
The IBM PC and IBM's Token Ring LAN 1981-1982
IBM entered the personal computer business leveraging external economies rather than doing everything internally as had done successfully with the System/360.Missing: deployments 1990s maximum nodes
[43]
[PDF] A Comparison of Industrial Communications Networks
Mini-Manufacturing Automation Protocol (Mini. MAP) is an example of a collapsed OSI model. The original. MAP is a bus or tree token-passing LAN using coax cable ...
[44]
Why a Ring? - MIT
Because it uses repeaters, a ring network can with ease span much greater physical distances than can the passive broadcast net. The passive broadcast net can ...
[45]
[PDF] LABORATORY FOR COMPUTER SCIENCE it MASSACHUSETTS
Jan 7, 1984 · The MIT Laboratory for Computer Science 10 Megabit token ring local area network was monitored. Over a one-week period 7 million packets and ...
[46]
How do you set up a redundant optical ring with PROFIBUS OLMs?
Nov 30, 2005 · Instructions: The diagram below shows how to set up a redundant optical ring with PROFIBUS OLMs: Fig. 1: Redundant optical PROFIBUS ring.Missing: topology | Show results with:topology
[47]
(PDF) Real-time fieldbus communications using Profibus networks
Aug 9, 2025 · This paper provides a comprehensive study on how to use Profibus fieldbus networks to support real-time industrial communications, that is, ...
[48]
Synchronous Optical Network Market Size & Forecast 2025-2032
Global synchronous optical network market is estimated to be valued at USD 7.33 billion in 2025 and is expected to reach USD 13.24 billion by 2032.Missing: ring | Show results with:ring<|separator|>
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[PDF] Introduction to DWDM Technology - Cisco
Early WDM began in the late 1980s using the two widely spaced wavelengths in the 1310 nm and. 1550 nm (or 850 nm and 1310 nm) regions, sometimes called wideband ...Missing: campus | Show results with:campus
[50]
Hybrid WDM Ring-Bus Optical Network - IEEE Xplore
This hybrid optical network allows dual operation of ring and bus topologies, and by incorporating WDM (wavelength division multiplexing) multiple protocolsMissing: DWDM Ethernet
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Revolutionizing Datacenter Networks via Reconfigurable Topologies
May 13, 2025 · New optical switching technologies are enabling a shift toward dynamically reconfigurable network topologies.<|separator|>
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Types of Network Topologies Explained - Cato Networks
Software-Defined Networking (SDN): SDN allows network topologies and routing to be defined and managed using code at the logical level. This enables ...Logical Network Topology · Network Monitoring Best... · How To Select The Right...<|control11|><|separator|>
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6 types of network topologies - TechTarget
May 5, 2022 · A ring topology is a configuration where every device directly connects to two other devices on a network, forming a continuous circle in a ...1. Bus Network Topology · 2. Ring Network Topology · 5. Tree Network Topology
[54]
Types of Network Topologies: Definitions and Use Cases - NetAlly
Bus Topology. In a bus topology, all devices share a single communication line or bus. Data from the network's source travels in both directions to all devices.Missing: misconceptions | Show results with:misconceptions
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Logical vs. physical topology: What's the difference? - TechTarget
Oct 25, 2024 · A network topology is the physical and logical layout that illustrates how a network functions. It serves as a map, guiding engineers just as a city map guides ...
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What Is a Token Ring? | phoenixNAP IT Glossary
Feb 26, 2025 · Token ring is a LAN technology using a token-passing protocol to manage access, ensuring only the device with the token can transmit data.Types Of Token Ring · How Does Token Ring Work? · The Advantages And...<|control11|><|separator|>
[57]
Understanding Token Ring - Ardent Tool of Capitalism
When a node that wants to transmit receives a token, it changes the token into a frame, appending its address, the recipient's address, and the data (see figure ...
[58]
Network Topology and Diagrams: Everything You Need to Know
In a ring topology, a daisy chain of connected devices forms a closed loop. Data travels in one direction from the source until it reaches its destination. An ...
[59]
Token Ring - Black Box
The IEEE ratified the Token ring LAN speeds of 4 Mbit/s and 16 Mbit/s in the IEEE 802.5 standard. Token Ring cabling. The original Token Ring specifications ...