The Clash of Industrial Switch Topologies: An In-Depth Technical Competition Between Star and Chain Topologies
In the underlying architecture of the industrial internet, network topology is akin to road network planning in a transportation system, directly influencing data transmission efficiency and reliability. In current industrial scenarios, the competition between star topology and chain topology has reached a fever pitch: the former dominates the mainstream market with centralized control and high fault tolerance, while the latter continues to penetrate specific scenarios with its advantages of minimal cabling and low cost. This article will conduct an in-depth comparison from three dimensions—technical principles, application scenarios, and cost-effectiveness—and reveal the applicable boundaries of the two topologies by incorporating real-world deployment cases of the industrial switch USR-ISG series.
The core advantage of star topology lies in its "hub-and-spoke" architecture. All devices are connected to a central switch (e.g., the USR-ISG208S-SFP with 8 Gigabit electrical ports + 2 SFP optical ports) via independent links, forming a radial structure similar to a wheel. This design brings three major technical benefits:
Deterministic Fault Isolation: When a link is interrupted (e.g., the network cable of a PLC is damaged), only a single device is affected. The MAC address table of the central switch can update routing in real-time, ensuring uninterrupted communication for other nodes. A case study in an automotive manufacturing workshop showed that after adopting star topology, network downtime caused by equipment failures decreased from 2.3 hours/year under chain topology to 0.7 hours/year.
Flexible Bandwidth Allocation: The central switch can dynamically adjust priorities through QoS policies. For example, the USR-ISG208S-SFP supports IEEE 802.1p/1Q standards, allowing motion control instructions from welding robots to be marked as high priority, ensuring exclusive access to Gigabit bandwidth, while image data from visual inspection systems is transmitted via the remaining bandwidth.
Exponential Improvement in Management Efficiency: Through the SNMPv3 protocol, administrators can remotely monitor over 200 parameters of USR-ISG switches, such as port status and traffic statistics. In a substation automation project, after adopting star topology, the number of on-site inspections by operations and maintenance personnel decreased from four times per month to once, and fault location time was reduced from 45 minutes to 8 minutes.
The survival logic of chain topology is rooted in its "minimalist" design. Devices are connected end-to-end to form a linear link, like a string of pearls. This structure demonstrates unique value in specific scenarios:
Extreme Compression of Cabling Costs: In long-distance deployment scenarios (e.g., highway tunnel monitoring), chain topology can save over 50% in cabling costs. A tunnel project adopted a serial deployment of USR-ISG1005 5-port Gigabit switches, reducing optical cable laying by 3.2 kilometers compared to star topology.
Innovative Breakthrough in Redundancy Design: Through "hand-in-hand" ring network technology, chain topology can achieve redundancy protection similar to that of a ring. When a link segment is interrupted, switches automatically switch to a backup path with a switching time of less than 50ms. A wind farm project adopted this technology, increasing annual availability from 99.2% to 99.997%.
Precision in Latency Control: In deterministic network scenarios (e.g., motion control), the fixed path of chain topology can eliminate microsecond-level jitter caused by switch forwarding in star topology. A case study in a semiconductor factory showed that chain topology reduced the synchronization error of robotic arms from ±50μs to within ±5μs.
The Dominion of Star Topology:
High-Density Device Scenarios: In a smart manufacturing workshop, a single USR-ISG208S-SFP can connect 8 PLCs, 4 robot controllers, and 2 HMIs, achieving logical isolation through VLAN division. A car body welding workshop adopted this solution, reducing network conflict rates from 12% to 0.3%.
Critical Infrastructure Scenarios: In substation automation systems, the centralized management advantages of star topology are particularly prominent. The USR-ISG switch's IEC 61000-4-5 surge immunity certification (4kV) and wide temperature operating range (-40°C to 85°C) can withstand extreme environments such as lightning strikes and electromagnetic interference.
Scenarios Requiring Flexible Expansion: The "plug-and-play" feature of star topology supports rapid capacity expansion. When a logistics warehouse added 20 AGVs, network expansion was completed within 2 hours by simply adding port modules to the central switch.
The Survival Space of Chain Topology:
Linear Layout Scenarios: In rail transit traction power supply systems, chain topology can be deployed linearly along the contact network, reducing optical cable bending losses. A high-speed rail project adopted a chain network of USR-ISG1005 switches, deploying one switch every 2 kilometers and reducing total costs by 37%.
Resource-Constrained Scenarios: In explosion-proof areas, the minimalist design of chain topology can reduce device power consumption. The fanless design (power consumption <8W) and IP40 protection rating of the USR-ISG1005 meet the requirements of flammable and explosive environments such as oil refineries.
Deterministic Transmission Scenarios: In power line carrier communication (PLC), the fixed path of chain topology can eliminate random delays caused by switch buffering in star topology. A smart grid project adopted this solution, reducing fault location time from minutes to seconds.
Constructing a TCO (Total Cost of Ownership) model for topology selection requires considering three dimensions:
Initial Investment: Star topology requires the deployment of a central switch, resulting in higher costs; chain topology only requires basic switches, with initial costs 30%–50% lower.
Operations and Maintenance Costs: The centralized management of star topology can reduce the frequency of manual inspections, resulting in long-term operations and maintenance costs over 40% lower; fault troubleshooting in chain topology requires segment-by-segment detection, with operations and maintenance costs increasing exponentially with link length.
Business Interruption Losses: The fault isolation feature of star topology can limit business interruption time to minutes; a single point of failure in chain topology may cause a network-wide outage. A case study in a chemical enterprise showed that annual business interruption losses under chain topology were 3.2 times those under star topology.
Taking a 100-node industrial network as an example:
Star Topology Solution: Using 1 USR-ISG208S-SFP (approximately ¥8,000) + 100 network cables (approximately ¥15,000), with an initial investment of ¥23,000; 5-year operations and maintenance costs of ¥12,000; estimated annual business interruption losses of ¥5,000.
Chain Topology Solution: Using 20 USR-ISG1005 switches (approximately ¥12,000) + 2,000 meters of optical cable (approximately ¥8,000), with an initial investment of ¥20,000; 5-year operations and maintenance costs of ¥30,000; estimated annual business interruption losses of ¥16,000.
TCO Comparison: The 5-year total cost of star topology is ¥60,000, while that of chain topology is ¥78,000. Despite lower initial investment, the long-term costs of chain topology are significantly higher than those of star topology.
As the industrial internet evolves towards deterministic networks, time-sensitive networking (TSN), and other directions, topology structures are exhibiting two major trends:
The Rise of Hybrid Topologies: By combining the centralized control of star topology with the minimal cabling of chain topology, a "core-edge" architecture is formed. For example, in smart factories, the core layer adopts star topology to connect the MES system, while the edge layer adopts chain topology to connect production line equipment, achieving a balance between cost and reliability.
Empowerment by Intelligent Switches: New-generation industrial switches (such as the USR-ISG series) are integrating AI algorithms to dynamically optimize topology structures. For example, when detecting excessive load on a link, the switch can automatically trigger link aggregation, increasing bandwidth from 1Gbps to 2Gbps.
The competition between star topology and chain topology is essentially an eternal trade-off between "reliability" and "cost" in industrial networks. In scenarios such as critical infrastructure and high-density devices, the centralized control and high fault tolerance of star topology are irreplaceable; in scenarios such as linear layouts and resource constraints, the minimalist design and low-cost advantages of chain topology are hard to shake. With the technological iteration of industrial switches like the USR-ISG series, the boundaries between the two topologies are blurring—the future of industrial networks will undoubtedly be an era of intelligent topologies that are "selected on demand and dynamically adapted."
