774 Network Topology Types

774.1 Learning Objectives

By the end of this section, you will be able to:

Identify Topology Types: Recognize star, bus, ring, full mesh, and partial mesh configurations
Understand Topology Characteristics: Know the advantages and disadvantages of each type
Apply Topologies to IoT: Select appropriate topology for different IoT scenarios
Read Network Diagrams: Interpret logical topology symbols and conventions

774.2 Prerequisites

Topologies Introduction: Understanding of physical vs logical topology concepts

774.3 Logical Topologies Overview

Overview diagram comparing five logical topology types (star, extended star, bus, ring, full mesh, partial mesh) with simplified device symbols and connection lines showing data flow patterns — Figure 774.1: Logical topologies overview showing network data flow patterns

774.3.1 Purpose and Features

Logical topology explains network operation, not physical layout.

Key features: 1. Symbols - Simplified device icons 2. Flow lines - Represent connections and data flow 3. Layout - Hierarchical arrangement 4. Labels and addresses - Device identification and IP information

774.3.2 Network Device Symbols

Common symbols (Cisco-style):

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graph LR
    subgraph Symbols["Common Network Device Symbols"]
        R["Router<br/>(Routes between networks)"]
        S["Switch<br/>(Connects devices in LAN)"]
        FW["Firewall<br/>(Security boundary)"]
        AP["Access Point<br/>(Wireless connectivity)"]
        SRV["Server<br/>(Provides services)"]
        PC["Computer<br/>(End device)"]
        IOT["IoT Device<br/>(Sensor/Actuator)"]
    end

    style R fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style S fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style FW fill:#E67E22,stroke:#2C3E50,stroke-width:2px,color:#fff
    style AP fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style SRV fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style PC fill:#E67E22,stroke:#2C3E50,stroke-width:2px,color:#fff
    style IOT fill:#2C3E50,stroke:#16A085,stroke-width:2px,color:#fff
    style Symbols fill:#f0f0f0,stroke:#7F8C8D,stroke-width:2px

Note: No official international standards for network symbols (unlike electrical symbols). Cisco conventions are widely adopted.

774.3.3 Link Symbols

Symbol	Meaning
Solid line	Ethernet (wired)
Dashed line	Wireless connection
Wavy line	Serial connection
Lightning bolt	High-speed link
Thick line	Multiple connections bundled

774.3.4 Hierarchical Layout

Best practice: Arrange logical diagrams hierarchically

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graph TB
    Internet([Internet])

    subgraph Core["Core Layer (Top)"]
        R1[Router/Gateway]
    end

    subgraph Distribution["Distribution Layer"]
        SW1[Switch 1]
        SW2[Switch 2]
    end

    subgraph Access["Access Layer (Bottom)"]
        D1[Device 1]
        D2[Device 2]
        D3[Device 3]
        D4[Device 4]
        D5[Device 5]
        D6[Device 6]
    end

    Internet <--> R1
    R1 <--> SW1
    R1 <--> SW2
    SW1 <--> D1
    SW1 <--> D2
    SW1 <--> D3
    SW2 <--> D4
    SW2 <--> D5
    SW2 <--> D6

    style Internet fill:#7F8C8D,stroke:#2C3E50,stroke-width:2px,color:#fff
    style R1 fill:#2C3E50,stroke:#16A085,stroke-width:3px,color:#fff
    style SW1 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style SW2 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style Core fill:#f8f9fa,stroke:#2C3E50,stroke-width:2px
    style Distribution fill:#f8f9fa,stroke:#16A085,stroke-width:2px
    style Access fill:#f8f9fa,stroke:#E67E22,stroke-width:2px

Layout principles: - Core devices at top/center - Connected devices radiating outward - Two-way data flow understood - Hierarchy shows message routing

774.4 Star Topology

Figure 774.2: Star topology with central hub/switch connecting all devices

Configuration: All devices connect to central node (switch/hub)

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graph TD
    Hub[Central Hub/Switch]

    D1[Device 1]
    D2[Device 2]
    D3[Device 3]
    D4[Device 4]
    D5[Device 5]
    D6[Device 6]

    Hub --- D1
    Hub --- D2
    Hub --- D3
    Hub --- D4
    Hub --- D5
    Hub --- D6

    style Hub fill:#E67E22,stroke:#2C3E50,stroke-width:4px,color:#fff
    style D1 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D2 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D3 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D4 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D5 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D6 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff

Characteristics: - Easy to install and manage - Failure of one device doesn’t affect others - Easy to add/remove devices - Central node is single point of failure - Requires more cable than bus topology

IoT Use Cases: - Smart home with central hub - Office sensors connected to gateway - Industrial sensors to local controller

774.5 Extended Star Topology

Figure 774.3: Extended star topology with multiple star networks interconnected

Configuration: Multiple star topologies interconnected

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graph TD
    Core[Core Switch]

    SW1[Switch 1]
    SW2[Switch 2]
    SW3[Switch 3]

    D1[Device 1]
    D2[Device 2]
    D3[Device 3]
    D4[Device 4]
    D5[Device 5]
    D6[Device 6]
    D7[Device 7]
    D8[Device 8]
    D9[Device 9]

    Core --- SW1
    Core --- SW2
    Core --- SW3

    SW1 --- D1
    SW1 --- D2
    SW1 --- D3

    SW2 --- D4
    SW2 --- D5
    SW2 --- D6

    SW3 --- D7
    SW3 --- D8
    SW3 --- D9

    style Core fill:#2C3E50,stroke:#16A085,stroke-width:4px,color:#fff
    style SW1 fill:#E67E22,stroke:#2C3E50,stroke-width:3px,color:#fff
    style SW2 fill:#E67E22,stroke:#2C3E50,stroke-width:3px,color:#fff
    style SW3 fill:#E67E22,stroke:#2C3E50,stroke-width:3px,color:#fff
    style D1 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D2 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D3 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D4 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D5 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D6 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D7 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D8 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D9 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff

Characteristics: - Highly scalable - Fault tolerance (one switch fails, others continue) - Hierarchical management - More complex configuration

IoT Use Cases: - Multi-building campus network - Large industrial facility - Smart city infrastructure

774.6 Bus Topology

Bus topology diagram showing five devices connected in series along a single shared bus cable with terminators at both ends, illustrating minimal cabling but vulnerability to single cable failure — Figure 774.4: Bus topology with all devices connected to a single backbone cable

Configuration: All devices share common medium (bus)

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graph LR
    T1[Terminator]
    D1[Device 1]
    D2[Device 2]
    D3[Device 3]
    D4[Device 4]
    D5[Device 5]
    T2[Terminator]

    T1 ===|Bus Cable| D1
    D1 === D2
    D2 === D3
    D3 === D4
    D4 === D5
    D5 ===|Bus Cable| T2

    style T1 fill:#E67E22,stroke:#2C3E50,stroke-width:2px,color:#fff
    style T2 fill:#E67E22,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D1 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D2 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D3 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D4 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D5 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff

Characteristics: - Minimal cable required - Easy to extend - Well-suited for temporary networks - Bus failure affects entire network - Difficult to troubleshoot - Performance degrades with many devices

IoT Use Cases: - I2C sensor bus (on same PCB) - CAN bus in vehicles - Legacy building automation systems

774.7 Ring Topology

Ring topology diagram showing six devices connected in circular loop with directional arrows indicating token-based data flow clockwise around the ring, demonstrating equal access but vulnerability to single point failure — Figure 774.5: Ring topology with devices connected in circular pattern

Configuration: Devices connected in circular sequence

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graph LR
    D1[Device 1]
    D2[Device 2]
    D3[Device 3]
    D4[Device 4]
    D5[Device 5]
    D6[Device 6]

    D1 -->|Token Flow| D2
    D2 --> D3
    D3 --> D4
    D4 --> D5
    D5 --> D6
    D6 --> D1

    style D1 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D2 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D3 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D4 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D5 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D6 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff

Characteristics: - Equal access for all devices - Predictable performance - No collisions (token-based) - Single device failure can break ring - Difficult to reconfigure

IoT Use Cases: - Fiber optic industrial networks - FDDI (legacy) - Token Ring (legacy)

Modern variant: Dual ring for fault tolerance

774.8 Full Mesh Topology

Full mesh topology diagram showing five devices where each device has direct connections to all other devices (10 total connections forming complete graph), demonstrating maximum redundancy but high complexity and cost — Figure 774.6: Full mesh topology where every node connects to every other node

Configuration: Every device directly connected to every other device

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graph TD
    D1[Device 1]
    D2[Device 2]
    D3[Device 3]
    D4[Device 4]
    D5[Device 5]

    D1 --- D2
    D1 --- D3
    D1 --- D4
    D1 --- D5
    D2 --- D3
    D2 --- D4
    D2 --- D5
    D3 --- D4
    D3 --- D5
    D4 --- D5

    style D1 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D2 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D3 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D4 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D5 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff

Characteristics: - Maximum redundancy - No single point of failure - High fault tolerance - Multiple simultaneous connections - Expensive (many connections) - Complex configuration - Number of connections = n(n-1)/2

IoT Use Cases: - Zigbee mesh networks (automatic organization) - Critical infrastructure monitoring - Emergency communication systems

Example: 5 devices = 10 connections, 10 devices = 45 connections!

774.9 Partial Mesh Topology

Partial mesh topology diagram showing six devices with strategic connections (some fully meshed in core, others with single paths and two backup routes shown as dashed lines), balancing cost efficiency with selective redundancy for critical paths — Figure 774.7: Partial mesh topology with selective redundant connections for critical paths

Configuration: Some devices fully connected, others not

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graph TD
    D1[Device 1]
    D2[Device 2]
    D3[Device 3]
    D4[Device 4]
    D5[Device 5]
    D6[Device 6]

    D1 --- D2
    D1 --- D3
    D2 --- D3
    D2 --- D4
    D3 --- D5
    D4 --- D5
    D4 --- D6
    D5 --- D6
    D1 -.->|Redundant Path| D4
    D2 -.->|Redundant Path| D6

    style D1 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D2 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D3 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D4 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D5 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff
    style D6 fill:#16A085,stroke:#2C3E50,stroke-width:2px,color:#fff

Characteristics: - Balance between cost and redundancy - Critical paths have backup routes - Less expensive than full mesh - Not all devices have direct paths

IoT Use Cases: - Hybrid sensor networks - Multi-site WAN connections - Smart city infrastructure

774.10 Topology Selection Decision Tree

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flowchart TD
    Start["What are your<br/>IoT requirements?"]

    Q1{"Is reliability<br/>critical?<br/>(Mission-critical?)"}
    Q2{"Need self-healing<br/>without manual<br/>intervention?"}
    Q3{"Battery-powered<br/>sensors?"}
    Q4{"High bandwidth<br/>needed?<br/>(Video, audio)"}
    Q5{"More than<br/>30 devices?"}
    Q6{"Legacy system<br/>compatibility?"}

    Mesh["Full/Partial<br/>MESH<br/>Zigbee, Thread"]
    Star["STAR<br/>Wi-Fi, LoRaWAN"]
    Hybrid["HYBRID<br/>Star + Mesh"]
    Bus["BUS<br/>CAN, I2C"]
    Tree["TREE<br/>Extended Star"]

    Ex1["Smart factory<br/>Industrial IoT"]
    Ex2["Smart home<br/>Small office"]
    Ex3["Mixed deployment<br/>Video + sensors"]
    Ex4["Automotive<br/>Building automation"]
    Ex5["Campus network<br/>Multi-building"]

    Start --> Q1
    Q1 -->|"Yes"| Q2
    Q1 -->|"No"| Q4

    Q2 -->|"Yes"| Mesh
    Q2 -->|"No, manual OK"| Q5

    Q5 -->|"Yes"| Tree
    Q5 -->|"No"| Star

    Q4 -->|"Yes"| Q3
    Q4 -->|"No"| Q6

    Q3 -->|"Yes"| Hybrid
    Q3 -->|"No"| Star

    Q6 -->|"Yes"| Bus
    Q6 -->|"No"| Star

    Mesh --> Ex1
    Star --> Ex2
    Hybrid --> Ex3
    Bus --> Ex4
    Tree --> Ex5

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    style Q1 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Q2 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Q3 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Q4 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Q5 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Q6 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Mesh fill:#16A085,stroke:#2C3E50,color:#fff
    style Star fill:#16A085,stroke:#2C3E50,color:#fff
    style Hybrid fill:#16A085,stroke:#2C3E50,color:#fff
    style Bus fill:#16A085,stroke:#2C3E50,color:#fff
    style Tree fill:#16A085,stroke:#2C3E50,color:#fff
    style Ex1 fill:#7F8C8D,stroke:#2C3E50,color:#fff
    style Ex2 fill:#7F8C8D,stroke:#2C3E50,color:#fff
    style Ex3 fill:#7F8C8D,stroke:#2C3E50,color:#fff
    style Ex4 fill:#7F8C8D,stroke:#2C3E50,color:#fff
    style Ex5 fill:#7F8C8D,stroke:#2C3E50,color:#fff

774.11 Topology Scalability Comparison

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graph TB
    subgraph Scale["Scalability: 10 vs 50 vs 100 Nodes"]
        subgraph S10["10 Nodes"]
            Star10["Star: 10 links<br/>Cost: $"]
            Mesh10["Full Mesh: 45 links<br/>Cost: $$"]
            Bus10["Bus: 1 segment<br/>Cost: $"]
        end

        subgraph S50["50 Nodes"]
            Star50["Star: 50 links<br/>Cost: $$"]
            Mesh50["Full Mesh: 1,225 links<br/>Cost: $$$$$ IMPRACTICAL"]
            Bus50["Bus: 1 segment<br/>Performance: DEGRADED"]
        end

        subgraph S100["100 Nodes"]
            Star100["Star: 100 links<br/>May need hierarchy"]
            Mesh100["Full Mesh: 4,950 links<br/>IMPOSSIBLE"]
            Bus100["Bus: 1 segment<br/>UNUSABLE"]
        end
    end

    subgraph Formula["Connection Formula"]
        StarF["Star: n connections<br/>O(n) - Linear"]
        MeshF["Full Mesh: n(n-1)/2<br/>O(n²) - Quadratic"]
        PartialF["Partial Mesh: ~2-3n<br/>O(n) - Linear"]
    end

    subgraph Recommendation["Recommendation by Scale"]
        Small["< 30 nodes:<br/>Star or Full Mesh OK"]
        Medium["30-100 nodes:<br/>Partial Mesh or Tree"]
        Large["> 100 nodes:<br/>Hierarchical/Tiered"]
    end

    style Star10 fill:#16A085,stroke:#2C3E50,color:#fff
    style Mesh10 fill:#16A085,stroke:#2C3E50,color:#fff
    style Bus10 fill:#16A085,stroke:#2C3E50,color:#fff
    style Star50 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Mesh50 fill:#e74c3c,stroke:#2C3E50,color:#fff
    style Bus50 fill:#e74c3c,stroke:#2C3E50,color:#fff
    style Star100 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Mesh100 fill:#e74c3c,stroke:#2C3E50,color:#fff
    style Bus100 fill:#e74c3c,stroke:#2C3E50,color:#fff
    style StarF fill:#2C3E50,stroke:#2C3E50,color:#fff
    style MeshF fill:#2C3E50,stroke:#2C3E50,color:#fff
    style PartialF fill:#2C3E50,stroke:#2C3E50,color:#fff
    style Small fill:#16A085,stroke:#2C3E50,color:#fff
    style Medium fill:#E67E22,stroke:#2C3E50,color:#fff
    style Large fill:#2C3E50,stroke:#2C3E50,color:#fff

774.12 Topology Comparison Summary

Topology	Connections	Fault Tolerance	Complexity	Best For
Star	n	Low (hub = SPOF)	Simple	Small networks, central control
Extended Star	n	Medium (branch isolation)	Moderate	Multi-floor buildings
Bus	1 segment	Very Low	Simple	Legacy systems, PCB buses
Ring	n	Low (single break fails)	Moderate	Token-based systems
Full Mesh	n(n-1)/2	Very High	Complex	Critical systems (<30 nodes)
Partial Mesh	~2-3n	High	Moderate	Balanced cost/reliability

774.13 Summary

Star topology provides simple management with central hub but creates single point of failure
Extended star scales star topology through hierarchical layers
Bus topology uses minimal cabling but bus failure affects entire network
Ring topology offers equal access but single device failure can break the ring
Full mesh provides maximum redundancy but connection count grows quadratically
Partial mesh balances redundancy and cost by protecting only critical paths
Topology selection depends on device count, reliability needs, and budget

774.14 What’s Next

Continue to Topology Selection and Decision Framework for detailed guidance on choosing the right topology based on specific IoT requirements, including performance metrics, cost analysis, and real-world decision scenarios.