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10.2 What is Mesh?

2. Theoretical Background

2.1 What is a Mesh Network?

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A mesh network is a topology where each device (node) is interconnected, creating multiple paths for data. Unlike traditional networks that rely on a single central point (such as a router), a mesh network is decentralized.

How It Works

In a mesh network, each ESP32 node acts as both a sender and receiver, functioning as a repeater. This differs from a star network where communication only goes through one central hub. A mesh network is more decentralized, thus improving coverage and network reliability.

In this setup, one ESP32 acts as the root node, which connects the mesh network to an external network, while other nodes can serve as intermediate parents that forward data or as leaf nodes that only send and receive their own data. Data in the network is automatically routed through available nodes until it reaches the final destination, either another node within the mesh or an external network via the root node. This creates an efficient, flexible, and fault-tolerant network.

Key characteristics include:

  • Self-Healing: If one node fails, data is automatically rerouted through another available path.
  • Wide Coverage: Each node functions as a repeater, significantly extending signal range.

2.2 Topology Comparison: Mesh vs. Star

To understand the advantages, let’s compare it with the commonly used Star topology in home Wi-Fi.

  • Mesh

    Mesh Topology

    Connects devices directly, creating multiple paths for data. A mesh network is more flexible than a star network and requires fewer gateways to communicate with the same number of devices. However, it is more complex and costly compared to a star network. Mesh networks also lack universal standards, which may cause compatibility issues between devices from different vendors.

  • Star

    Star Topology

    Connects devices through a central hub. A star network is simpler and cheaper than a mesh network but depends heavily on the central hub. Device failures in a star network do not affect the rest of the system, but if the hub fails, the entire network goes down. Star networks are best suited for devices that need to communicate directly with a central node, such as office equipment, security cameras, and medical devices.

Component Mesh Topology Star Topology
Resilience Very High. Supports self-healing. Low. If the hub/router fails, the entire network fails.
Coverage Wide and flexible. Easy to expand. Limited by the hub/router’s range.
Complexity More complex to configure. Simple and easy to set up.

2.3 Types of Nodes in a Mesh Network

In this lab, we will learn about 4 types of nodes:

  • Root Node
    The root node is the highest-level node in a Wi-Fi mesh network and acts as the only link between the mesh network and the external IP network. It connects directly to a conventional Wi-Fi router and forwards data packets between the external network and the mesh nodes. There must only be one root node in a mesh network, and it can only have one upstream connection—to the router. The root node is crucial in ensuring that all mesh network data can be accessed by external devices.

  • Leaf Nodes
    Leaf nodes are nodes that have no child nodes (no downstream connections). They can only send or receive their own data packets and do not forward data from other nodes. Typically, leaf nodes are located at the farthest edge of the mesh where no new downstream connections are possible. If a node only has a station interface (station-only node) and lacks a softAP interface, it is designated as a leaf node since downstream connections require a softAP.

  • Intermediate Parent Nodes
    Intermediate parent nodes are neither root nor leaf nodes. They have one upstream connection (to a parent node) and may have multiple downstream connections (to child nodes). These nodes can send, receive, and forward data from both upstream and downstream connections. Unlike leaf nodes, they can still form downstream connections in the future. They serve as bridges in the mesh network, enabling data to flow between different layers.

  • Idle Nodes
    Idle nodes are nodes that have not yet joined the mesh network. They attempt to establish an upstream connection with an existing intermediate parent node or try to become the root node if certain conditions are met (for example, when no root node exists in the network). Idle nodes remain passive until they successfully join or are integrated into the mesh network.

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