Mesh

Relay Node

<\/script>\n
'; }, get iframeSnippet() { const domain = '{ SITE_DOMAIN }'; const type = '{ embed_type }'; const slug = '{ embed_slug }'; return ''; }, get activeSnippet() { return this.method === 'script' ? this.scriptSnippet : this.iframeSnippet; }, copySnippet() { navigator.clipboard.writeText(this.activeSnippet).then(() => { this.copied = true; setTimeout(() => { this.copied = false; }, 2000); }); } }" @keydown.escape.window="open = false" @click.outside="open = false">

Embed This Widget

Theme


      
    


    
    

      Widget powered by
      .
      Free, no account required.
    

  





    
    

    
    

      
A Mesh node that retransmits received messages to extend the network's communication range.

    


    
    
    

      Also known as:
      
      Relay
      
    

    
  


  




  
  

    
What Is a Relay Node?


A Relay Node is a Bluetooth Mesh node that retransmits received mesh messages on the advertising channels to extend the network's communication range. Relay nodes are the backbone of the managed flooding delivery mechanism, enabling messages to hop across multiple radio ranges and reach devices that are not within direct range of the originator.


How Relaying Works


When a relay node receives a mesh Network PDU on an advertising channel, it performs the following steps:


    

  1. Decrypt the network layer using the Network Key (NetKey) to verify the message belongs to this network.
    2. 

  2. Check the cache for duplicates (source address + sequence number). If already seen, silently drop.
    3. 

  3. Decrement TTL by 1. If the resulting TTL is 0 or 1, do not relay (TTL 1 means the message was intended for one more hop, which this node has consumed).
    4. 

  4. Re-encrypt with the NetKey (updating the network nonce with the new TTL).
    5. 

  5. Retransmit on the advertising channels after a small random delay.
    6. 



The relay node does not need to decrypt the application layer (AppKey) to forward the message. It operates purely at the network layer, which means relay nodes cannot read application payloads -- an important security property.


Relay Retransmit Parameters


Each relay node has configurable retransmit settings:


    

  • Relay Retransmit Count (0 -- 7): number of retransmissions of a relayed message. The total transmissions = Count + 1. A typical value is 2 (three total transmissions).
    • 

  • Relay Retransmit Interval Step (10 -- 320 ms, in 10 ms steps): delay between retransmissions. Randomized jitter is added to reduce collisions.
    • 



These parameters are configured via the Configuration Server model by the provisioner or a Configuration Client.


Which Nodes Should Relay


Not every node should be a relay. Enabling relay on all nodes in a dense network causes excessive advertising channel congestion. General guidelines:






Scenario
Recommendation






Mains-powered nodes (lights, outlets)
Enable relay




Battery-powered sensors
Disable relay (use Low Power Node instead)




Dense deployment (> 1 node per 3 m)
Enable relay selectively (every 2nd or 3rd node)




Linear topology (hallway)
Enable relay on every node along the path






Power Consumption


Relaying requires the node to keep its radio in receive mode on the advertising channels continuously (or with a high duty cycle). This is incompatible with battery operation in most practical deployments. Relay nodes are therefore almost always mains-powered. The continuous scanning draws 5 -- 15 mA depending on the SoC, which is negligible for mains-powered devices but would drain a coin cell in hours.


Relay vs. Directed Forwarding


With Directed Forwarding (Mesh 1.1), messages can follow pre-discovered paths instead of being flooded through all relays. Directed forwarding nodes maintain a small forwarding table and only relay messages that match a known path entry. This dramatically reduces airtime in large networks while still using relay nodes for group-addressed or unknown-destination messages.

  

  

  
  
  




  
  
Related Terms

  

  

    
    Bluetooth Mesh
    
    Managed Flooding
    
  





  

  
  

  
  

  
  
  

    
Related Content

    

      
      
        

          
          
Bluetooth Mesh Networking: Architecture and Concepts

          
          Mesh & Audio
          
        

        
        
        
…Not every mesh node has the same role: Node Type Function Relay Node Re-broadcasts received messages, extends range Friend Node…

        
      
      
      
        

          
          
Mesh 1.1: Directed Forwarding and Subnet Bridging

          
          Mesh & Audio
          
        

        
        
        
…Classic Bluetooth Mesh uses managed flooding : every relay node rebroadcasts every packet it receives (TTL permitting). In…

        
      
      
      
        

          
          
Bluetooth Mesh Implementation: From Provisioning to Production

          
          Mesh & Audio
          
        

        
        
        
…managed flooding approach where messages propagate through relay nodes , eliminating the need for a central hub and…

        
      
      
      
        

          
          
BLE Smart Home: Locks, Sensors, and Home Automation

          
          Industry Applications
          
        

        
        
        
…lighting networks without a hub. The managed flooding relay architecture: Provisioner (phone/hub) sends provisioning…

        
      
      
    

  

  

  
  




  
Frequently Asked Questions


  

    
    

      
      

        
Our glossary covers 90+ BLE technical terms organized by category. Each term includes a definition, related terms, and links to relevant chips and guides.